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1
Childs, Conrad James. « The structure and hydraulic properties of fault zones ». Thesis, University of Liverpool, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.367208.
Texte intégral
2
Soden, Aisling Mary. « The initiation and evolution of ignimbrite faults, Gran Canaria, Spain ». Connect to e-thesis, 2008. http://theses.gla.ac.uk/191/.
Texte intégralRésumé :
Thesis (Ph.D.) - University of Glasgow, 2008.Ph.D. thesis submitted to the Department of Geographical and Earth Sciences, Faculty of Physical Sciences, University of Glasgow, 2008. Includes bibliographical references. Print version also available.
3
Fondriest, Michele. « Structure and mechanical properties of seismogenic fault zones in carbonates ». Doctoral thesis, Università degli studi di Padova, 2014. http://hdl.handle.net/11577/3424540.
Texte intégralRésumé :
In many seismically active areas (e.g. Italy, Greece) earthquakes, sometimes destructive, nucleate within (aftershocks surely do) and propagate through carbonates in the upper crust (e.g. L’Aquila earthquake, 2009, Mw 6.1). Seismology, geophysics and geodesy furnish key parameters related to the earthquake source (e.g. seismic moment, static stress drop, radiated energy) but lack sufficient resolution to constrain detailed three-dimensional fault zone geometry and coseismic on- and off-fault deformation processes at scales relevant to earthquake physics.
In this thesis it is proposed to study the internal structure and mechanics of fault zones hosted in carbonate rocks using a multidisciplinary approach, complementary to the seismological-based one. This includes detailed structural survey to quantify the architecture of exhumed fault zones in carbonates both by field and remote sensed methods (e.g. use of a drone to get high-resolution aerial images), rock deformation experiments under conditions relevant to the seismic cycle (e.g. use of rotary shear apparatus, uniaxial press, Split Hopkinson Pressure Bar), microstructural-mineralogical characterization (optical and scanning electron microscopy, electron microprobe analyses, X-ray powder diffraction, cathodoluminescence, X-ray microtomography, white light interferometry, image analysis) of natural and experimental fault rocks to infer the physico-chemical processes occurring during earthquakes.
Two fault zones cutting dolostones exhumed from < 3 km depth in the Italian Southern Alps were described: the Borcola Pass Fault Zone (BPFZ) and the Foiana Fault Zone (FFZ). In both cases the internal structure of the two fault zones was strongly influenced by the reactivation of preexisting anisotropies such as regional-scale joint sets and bedding surfaces.
The BPFZ is a secondary strike-slip branch of the regional Schio-Vicenza Line that developed in a fluid-rich upper crustal environment. The microstructural characteristics of the principal and secondary slip zones of the BPFZ, including detailed analysis of the clast size distribution of injected cataclasites, suggested coseismic fluidization processes during faulting, most likely related to the propagation of ancient seismic ruptures in to the shallow crust.
The FFZ is a major sinistral transpressive fault zone that developed in a fluid-poor upper crustal setting. Systematic along-strike and down-dip changes in the structure of the FFZ were recognized, allowing a comparison to be made between field observations and the predictions of three-dimensional earthquake rupture simulations. A noteworthy characteristic of the FFZ is the presence of thick belts (hundreds of meters) of in-situ shattered dolostones cut by discrete mirror-like fault surfaces.
The origin of mirror-like fault surfaces and in-situ shattered dolostones in the FFZ was investigated using, respectively, low- to high-velocity (0.0001-1 m/s) rotary shear friction experiments on dolostone gouges and low- to high-strain rate (quasi-static 10-3 s-1, dynamic > 50 s-1) uniaxial compression tests on dolostone rock cylinders. At applied normal stresses and displacements consistent with those estimated for the FFZ, experimental mirror-like fault surfaces comparable to the natural examples (e.g. clast truncation along fault surfaces, similar surface roughness) were formed in rotary-shear experiments only at seismic slip rates (v ≥ 0.1 m/s). I suggest therefore that small-displacement mirror-like fault surfaces developed in dolostone gouge layers represent markers of seismic slip. In-situ shattered dolostones similar to those found within the FFZ (i.e. rock fragments up to a few millimeters in size elongated in the stress wave loading direction, incipient zones of microfracturing down to the micrometer scale) were formed during uniaxial compression tests only above strain rates of ~ 200 s-1. The association of in-situ shattered dolostones cut by discrete mirror-like fault surfaces is interpreted to record the propagation of multiple earthquake ruptures within the shallow crustal portions of the FFZ.
Lastly, the structural complexity of the studied fault zones in terms of three-dimensional geometry of the fault-fracture network, fault rock spatial distribution, fault orientation and kinematics, compares favorably to the predicted damage distribution in three-dimensional earthquake rupture simulations, as well as the structure of active seismic sources hosted in carbonate rocks as illuminated by seismological techniquesIn molte regioni sismiche dell’area Mediterranea, tra cui l’Italia e la Grecia, gran parte dei terremoti, anche distruttivi, enucleano e propagano in sequenze di rocce carbonatiche della crosta superiore (terremoto dell’Aquila, 2009, Mw 6.1). Questo è vero soprattutto per le sequenze di foreshock e aftershock. Le indagini sismologiche, geofisiche e geodetiche forniscono dei parametri fondamentali per la caratterizzazione delle sorgenti sismiche (momento sismico, caduta di sforzo statico, energia elastica irradiata) ma non hanno risoluzione spaziale sufficiente per descrivere in maniera dettagliata la geometria delle sorgenti sismiche e i processi chimico-fisici attivi nelle zone di faglia durante un terremoto. Questi aspetti limitano fortemente la nostra conoscenza della fisica dei terremoti. In questa tesi la struttura interna e le proprietà meccaniche di zone di faglia sismogenetiche in rocce carbonatiche sono state studiate utilizzando un approccio multidisciplinare e complementare rispetto a quello classico basato su dati sismologici principalmente ricavati dall’inversione delle onde sismiche. I metodi utilizzati sono: (i) il rilevamento strutturale di dettaglio di zone di faglia esumate in carbonati con tecniche di terreno e di telerilevamento (ad es. utilizzo di un drone per ottenere immagini ad alta risoluzione di grandi affioramenti), (ii) la realizzazione di prove meccaniche su roccia (e polveri di roccia) in condizioni di deformazione rilevanti per il ciclo sismico (utilizzo di apparati di tipo rotary, pressa uniassiale e Split Hopkinson Pressure Bar), (iii) lo studio mineralogico-microstrutturale (microscopia ottica e a scansione elettronica, microsonda elettronica, diffrazione a raggi X su polveri, catodoluminescenza, microtomografia a raggi X, interferometria in luce bianca, analisi di immagine) di rocce di faglia naturali e sperimentali per vincolare i processi chimico-fisici attivi in carbonati durante un terremoto. Sono state selezionate due zone di faglia in dolomie: la zona di faglia del Passo della Borcola (BPFZ) e la zona di faglia di Foiana (FFZ). Entrambe le zone di faglia sono esumate da profondità < 3 km e affiorano nel settore delle Alpi Meridionali (Italia). L’architettura interna delle due zone di faglia è fortemente controllata dalla riattivazione di strutture ereditate come sistemi di giunti a scala regionale e superfici di strato. La BPFZ è una faglia secondaria trascorrente appartenente al sistema della Linea Schio-Vicenza. La presenza all’interno della BPFZ di zone di scivolamento estremamente localizzate e spesso organizzate in livelli cataclastici ed ultracataclastici con bordi irregolari (a lobi e cuspidi), iniettati lungo fratture estensionali e caratterizzati da una forte selezione granulometrica ha suggerito l’attivazione di fenomeni di fluidizzazione durante la propagazione di rotture sismiche in un ambiente ricco in fluidi. La FFZ è una faglia transpressiva sinistra a scala regionale che presenta sistematiche variazioni nella propria struttura interna (e.g. spessore della zona di faglia, orientazione e cinematica delle faglie minori) lungo la direzione e l’immersione della faglia. La zona di faglia esposta è caratterizzata dalla presenza di dolomie frantumate senza evidenze significative di deformazione per taglio (dolomie frantumate in-situ) associate a faglie con piccoli rigetti (< 0.5 m) e superfici a specchio con clasti troncati. L’assenza di vene o fratture sigillate indica che la fagliazione è avvenuta in un ambiente povero in fluidi. L’origine delle faglie con superfici a specchio e delle dolomie frantumate in-situ della FFZ è stata investigata attraverso esperimenti eseguiti (1) con un apparato di tipo rotary imponendo basse ed alte velocità (0.0001-1 m/s) di scivolamento su polveri di dolomia e (2) con un pressa uniassiale e una Split Hopkinson Pressure Bar imponendo basse ed alte velocità di deformazione (quasi-statiche 10-3 s-1, dinamiche > 50 s-1) su cilindri di dolomia. Applicando le condizioni di sforzo normale e rigetto stimate per le faglie della FFZ, superfici a specchio simili a quelle naturali in termini di rugosità delle superfici e di microstrutture (presenza di clasti troncati lungo le superfici di faglia), sono state prodotte negli esperimenti di tipo rotary solo a velocità di scivolamento cosismiche (v ≥ 0.1 m/s). Inoltre dolomie frantumate in-situ con microstrutture simili a quelle descritte lungo la FFZ (frammenti di roccia con dimensioni fino a qualche millimetro allungati nella direzione di applicazione del carico e zone di microfratturazione incipiente) sono state prodotte negli esperimenti con la Split Hopkinson Pressure Bar solo a ratei di deformazione > 200 s-1 : tali ratei di deformazione sono in genere associati alle perturbazioni di sforzo dovute al passaggio di una rottura sismica. Pertanto l’associazione di dolomie frantumate in-situ tagliate da faglie discrete con superfici a specchio è stata interpretata come il risultato della propagazione di rotture sismiche nelle porzioni superficiali della FFZ. Infine, a livello qualitativo, la complessità strutturale delle due zone di faglia studiate in termini di geometria del network di faglie e fratture, distribuzione spaziale delle rocce di faglia, orientazione e cinematica delle faglie, è confrontabile sia con la distribuzione del danneggiamento di faglia predetta da simulazioni di rotture sismiche, sia con la struttura di sorgenti sismogenetiche attuali in carbonati desunta da osservazioni sismologiche
4
Wu, Jiedi. « New Constraints on Fault-Zone Structure from Seismic Guided Waves ». Diss., Virginia Tech, 2008. http://hdl.handle.net/10919/28873.
Texte intégralRésumé :
The structure of fault zones (FZs) plays an important role in understanding fault mechanics, earthquake rupture and seismic hazards. Fault zone seismic guided waves (GW) carry important information about internal structure of the low-velocity fault damage zone. Numerical modeling of observed FZGWs has been used to construct models of FZ structure. However, the depth extent of the waveguide and the uniqueness of deep structure in the models have been debated. Elastic finite-difference synthetic seismograms were generated for FZ models that include an increase in seismic velocity with depth both inside and outside the FZ. Strong GWs were created from sources both in and out of the waveguide, in contrast with previous homogenous-FZ studies that required an in-fault source to create GW. This is because the frequency-dependent trapping efficiency of the waveguide changes with depth. The near-surface fault structure efficiently guides waves at lower frequencies than the deeper fault. Fault structure at seismogenic depth requires the analysis of data at higher frequencies than the GWs that dominate at the surface. Adapting a two-station technique from surface wave studies, dispersive differential group arrival times between two earthquakes can be used to solve for FZ structures between the earthquakes. This method was tested with synthetic data and shallow events recorded in the SAFOD borehole in the San Andreas Fault. A pair of deep earthquakes recorded in the SAFOD borehole indicate a ~150 m wide San Andreas Fault waveguide with >20% velocity contrast at 10-12 km depth. With additional earthquakes, the full FZ structure at seismogenic depth could be imaged. Subsurface FZ structure can also be derived from a surface source and receiver array analogous to a body-wave refraction survey. Synthetic seismograms for such source-receiver geometry were generated and verified that FZGWs are refracted by the increase in velocity with depth. Synthetic data from a surface array were successfully inverted to derive FZ structure in the subsurface. The new methods presented in this dissertation extend the potential of FZGWs to image deeper FZ structure than has been uniquely constrained in the past.Ph. D.
5
Robeson, Kim R. « Three-Dimensional Structure of Small Strike-Slip Fault Zones in Granitic Rock : Implications for Fault-Growth Models ». DigitalCommons@USU, 1998. https://digitalcommons.usu.edu/etd/5608.
Texte intégralRésumé :
Three small strike-slip fault zones exposed in granitic rock in the central Sierra Nevada, California, provide field-based data to construct three-dimensional 11 representations of each fault zone in order to compare with the geometries predicted by existing fault-growth models. All three fault zones are nearly vertical, strike -N60°E, and have left-lateral slip. The fault zones range from 60 to 140 min length and 1 to 12 m wide. Each fault zone consists primarily of parallel to subparallel fracture and fault traces 2 to 56 m long and is separated 25 cm to 7 m by intact rock. One fault zone contains two simple fault zones that consist of fractured rock separated from relatively unfractured rock by two nearly parallel boundary faults. Fracture and fault trace characteristic s are a function of fault zone development and complexity. Traces interconnect primarily by way of junctions and steps, with traces branching away from each other at junctions having angles between 10° to 80° whereas steps branch away at angles between 10° to 40°. Faults terminating as a splay or horsetail splay are rare. Splay fractures strike away from the fault traces at angles of 10° to 60°.
Individual faults and the fault zones have irregular displacement-length profiles. Episodic brittle fracturing, hydrothermal mineralization, and alteration are pervasive along fractures and faults. Thickness, composition, and location of hydrothermal mineralization and alteration along fault traces show no consistent pattern and indicate a brittle strain softening process occurred . The widespread distribution of chlorite-epidote mineralization suggests that each fault zone acts as a through-going passageway for fluids.
Fault-growth models involving the in-plane propagation of shear displacement along faults and having strain as the boundary condition match the field data the best. All three fault zones resemble those fault-growth models in which fault zone development is a nonuniform process with the growth of individual fractures and faults affecting the nucleation, propagation, and geometry of subsequent fractures and faults. Three-dimensional representation of these fault zones will constrain spatial statistical and stochastic modeling of fault zone nucleation and propagation.
6
Loveless, Sian. « The hydrogeological structure of fault zones in poorly lithified sediment, Gulf of Corinth rift ». Thesis, University of East Anglia, 2013. https://ueaeprints.uea.ac.uk/47856/.
Texte intégralRésumé :
Often, the structure of fault zones cutting poorly lithified sediment examined in outcrop indicate such fault zones should behave as hydraulic barriers, but hydrological observations indicate they behave as conduit-barriers. This thesis investigates the hydrogeological structure of fault zones cutting poorly lithified sediment to better understand the observed conduit-barrier behaviour. The macro- and micro-structure of fault zones was investigated at outcrops of five fault arrays cutting syn-rift sediment of the rapidly extending Gulf of Corinth rift, Central Greece. Fault zone evolution was interpreted from these observations and changes to sediment hydraulic characteristics in fault zones estimated. Based upon the field data, characteristic fault zone hydrogeological structure was represented in two-dimensional numerical fluid-flow models in order to assess likely hydraulic impacts. Fault zone structure is found to be dominated by a mixed zone and differs to those previously reported. Two models of fault zone evolution are proposed for faults cutting: 1. Only poorly lithified sediment, in which beds are rotated and smeared in the mixed zone, where these can mix at the grain-scale through distributed, controlled particulate flow. 2. Sediment of contrasting competency, with mixed zones comprising blocks and lenses, and fine-grained smears in which strain localisation and fault-tip bifurcation are central to their evolution. Both models apply to fault zones that juxtapose fine and coarse-grained sediment. Numerical models show that the majority of these fault zones will behave as barriers to fluid-flow due to a reduction in hydraulic conductivity. Fault zones of all sizes influence fluid-flow, but hydraulic impact increases with fault throw. Conduit-barrier behaviour can be explained by anisotropies, particularly from slip-surface cataclasites, in fault zones cutting poorly lithified sediment only. Fault hydraulic behaviour is strongly dependent on structural hetereogeneities and their geometry in the fault zone. The cumulative effects of these faults will be significant for subsurface fluid-flow.
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Ellen, Rachael. « Predicting the internal structure of fault zones in basalt sequences, and their effect on along- and across-fault fluid flow ». Thesis, University of Strathclyde, 2012. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=25466.
Texte intégralRésumé :
Interest in the architecture and fluid flow potential of fault zones in basalt sequences has intensified over recent years, due to their applications in the hydrocarbon industry and CO₂ storage. In this study, field mapping is combined with micro-structural analyses and flow modelling to evaluate fault growth, evolution, fluid-rock interactions, and permeability changes over time in faults in basalt sequences. Twelve brittle fault zones cutting basalt sequences in the North Atlantic Igneous Province were studied. This study finds that fault architecture is ultimately controlled by displacement and juxtaposition. Self-juxtaposed faults (i.e. basalt faulted against itself) are characterised by wide zones of brecciation, cataclasis, fracturing, mineralisation and alteration. Non self-juxtaposed faults (i.e. basalt faulted against an inter-lava unit) are characterised by relatively narrow principal slip zones, filled with clay smears or clay-rich gouge derived from inter-lava beds. This study also finds that brittle deformation of basalts at the grain scale is mineralogy dependent. Fe-Ti oxides and pyroxenes deform by intragranular fracturing and grain size reduction, whereas olivines and feldspars are susceptible to replacement by clay and zeolites. Fault rock bulk chemistries are likely to differ from their host rocks, and this is controlled by secondary mineral formation, with zeolite and clay minerals playing an important role. Flow modelling in this study shows that controls on along- and across-fault fluid flow can significantly change fault zone bulk permeability over time, as a result of mineralisation and alteration of the fault zone as it evolves. The results from this study are used to propose a model for how fault strength, fault-related alteration, and permeability change over time in fault zones in basalt sequences. Results highlight the impact that fault-related alteration could have on CO₂ storage. A predictive model for fault structure at depth, developed from this study's findings, is presented for fault zones in basalt sequences, which has particular relevance to the hydrocarbon and CO₂ industry.
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Nishiwaki, Takafumi. « Comparison of Damage Zones of the Nojima and the Asano Faults from the Deep Drilling Project : Differences in Meso-to-microscale Deformation Structures related to Fault Activity ». Kyoto University, 2020. http://hdl.handle.net/2433/253096.
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Hernandez, Moreno Catalina <1981>. « Understanding block rotation of strike-slip fault zones : Paleomagnetic and structural approach ». Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2015. http://amsdottorato.unibo.it/6829/1/Tesi_Catalina_Hdz_M_1.pdf.
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This thesis is focused on the paleomagnetic rotation pattern inside the deforming zone of strike-slip faults, and the kinematics and geodynamics describing it.
The paleomagnetic investigation carried out along both the LOFZ and the fore-arc sliver (38º-42ºS, southern Chile) revealed an asymmetric rotation pattern. East of the LOFZ and adjacent to it, rotations are up to 170° clockwise (CW) and fade out ~10 km east of fault. West of the LOFZ at 42ºS (Chiloé Island) and around 39°S (Villarrica domain) systematic CCW rotations have been observed, while at 40°-41°S (Ranco-Osorno domain) and adjacent to the LOFZ CW rotations reach up to 136° before evolving to CCW rotations at ~30 km from the fault. These data suggest a directed relation with subduction interface plate coupling. Zones of high coupling yield to a wide deforming zone (~30 km) west of the LOFZ characterized by CW rotations. Low coupling implies a weak LOFZ and a fore-arc dominated by CCW rotations related to NW-sinistral fault kinematics.
The rotation pattern is consistent with a quasi-continuous crust kinematics. However, it seems unlikely that the lower crust flux can control block rotation in the upper crust, considering the cold and thick fore-arc crust. I suggest that rotations are consequence of forces applied directly on both the block edges and along the main fault, within the upper crust.
Farther south, at the Austral Andes (54°S) I measured the anisotropy of magnetic susceptibility (AMS) of 22 Upper Cretaceous to Upper Eocene sites from the Magallanes fold-thrust belt internal domains. The data document continuous compression from the Early Cretaceous until the Late Oligocene. AMS data also show that the tectonic inversion of Jurassic extensional faults during the Late Cretaceous compressive phase may have controlled the Cenozoic kinematic evolution of the Magallanes fold-thrust belt, yielding slip partitioning.
10
Hernandez, Moreno Catalina <1981>. « Understanding block rotation of strike-slip fault zones : Paleomagnetic and structural approach ». Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2015. http://amsdottorato.unibo.it/6829/.
Texte intégralRésumé :
This thesis is focused on the paleomagnetic rotation pattern inside the deforming zone of strike-slip faults, and the kinematics and geodynamics describing it.
The paleomagnetic investigation carried out along both the LOFZ and the fore-arc sliver (38º-42ºS, southern Chile) revealed an asymmetric rotation pattern. East of the LOFZ and adjacent to it, rotations are up to 170° clockwise (CW) and fade out ~10 km east of fault. West of the LOFZ at 42ºS (Chiloé Island) and around 39°S (Villarrica domain) systematic CCW rotations have been observed, while at 40°-41°S (Ranco-Osorno domain) and adjacent to the LOFZ CW rotations reach up to 136° before evolving to CCW rotations at ~30 km from the fault. These data suggest a directed relation with subduction interface plate coupling. Zones of high coupling yield to a wide deforming zone (~30 km) west of the LOFZ characterized by CW rotations. Low coupling implies a weak LOFZ and a fore-arc dominated by CCW rotations related to NW-sinistral fault kinematics.
The rotation pattern is consistent with a quasi-continuous crust kinematics. However, it seems unlikely that the lower crust flux can control block rotation in the upper crust, considering the cold and thick fore-arc crust. I suggest that rotations are consequence of forces applied directly on both the block edges and along the main fault, within the upper crust.
Farther south, at the Austral Andes (54°S) I measured the anisotropy of magnetic susceptibility (AMS) of 22 Upper Cretaceous to Upper Eocene sites from the Magallanes fold-thrust belt internal domains. The data document continuous compression from the Early Cretaceous until the Late Oligocene. AMS data also show that the tectonic inversion of Jurassic extensional faults during the Late Cretaceous compressive phase may have controlled the Cenozoic kinematic evolution of the Magallanes fold-thrust belt, yielding slip partitioning.
11
Wessel, Zachary R. « Structural analysis of a potential peri-Gondwanan detachment : George River Suite-Bras d'Or Gneiss contact relations in the Creignish Hills, Cape Breton, Nova Scotia / ». Ohio : Ohio University, 2004. http://www.ohiolink.edu/etd/view.cgi?ohiou1091116487.
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Ryter, Derek. « Late Pleistocene kinematics of the central San Jacinto fault zone, southern California / ». view abstract or download file of text, 2002. http://wwwlib.umi.com/cr/uoregon/fullcit?p3072605.
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Thesis (Ph. D.)--University of Oregon, 2002.Typescript. Includes vita and abstract. Includes bibliographical references (leaves 131-137). Also available for download via the World Wide Web; free to University of Oregon users.
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Taylor, Rochelle Louise. « Acoustic velocity structure of the carboneras fault zone, SE Spain ». Thesis, University of Manchester, 2013. https://www.research.manchester.ac.uk/portal/en/theses/acoustic-velocity-structure-of-the-carboneras-fault-zone-se-spain(63a8ae72-04e3-4ab8-bf38-dc215cabbeec).html.
Texte intégralRésumé :
The Carboneras fault zone (CFZ, Almería Province, SE Spain) is a major NE-SW trending tectonic lineament that marks part of the diffuse plate boundary between Iberia and Africa. Developed within a basement terrain dominated by mica schist, the fault system comprises two main strands within a complex zone up to 1 km wide. Between these two strands is a braided network of left-lateral strike-slip, phyllosilicate-rich fault gouge bands, ranging between 1 and 20 m in thickness, passively exhumed from up to 3 km depth. The excellent exposure in a semi-arid environment, the wide range of rock types and fault structures represented and the practicality of carrying out in-situ geophysical studies makes this fault zone particularly well suited to verifying and interpreting the results of in-situ seismic investigations. Integration of elements of field study, laboratory analysis and modelling has aided interpretation of the internal structure of the fault zone. Ultrasonic measurements were made using standard equipment over confining and pore pressure ranges appropriate to the upper 10 km of the continental crust. Seismic velocities have also been approximated from modal analysis and mineral phase elastic properties and adjusted for the effects of porosity. In-situ seismic investigations recorded P-wave velocities 40-60% lower than those measured in the laboratory under corresponding pressures and at ambient temperatures for hard rock samples. Fault gouge velocities measured in the laboratory, however, are comparable to those measured in the field because, unlike the host rocks, fault gouges are only pervasively micro-fractured and lack the populations of long cracks (larger than the sample size) that cause slowing of the velocities measured in the field. By modelling the effect of fractures on seismic velocity (by superimposing upon the laboratory seismic data the effects of crack damage) the gap between field- and laboratory-scale seismic investigations has been bridged. Densities of macroscopic cracks were assessed by measuring outcrop lengths on planar rock exposures. Assuming crack length follows a power law relation to frequency, this fixes a portion of the power spectrum, which is then extrapolated to cover the likely full range of crack sizes. The equations of Budiansky and O'Connell (1976), linking crack density to elastic moduli, were used to calculate modified acoustic velocities, and the effects of the wide range of crack sizes were incorporated by breaking the distribution down into small sub-populations of limited range of crack density. Finally, the effect of overburden pressure causing progressively smaller cracks to close was incorporated to predict velocity versus depth of burial (i.e. pressure). Determination of rock physical properties from laboratory analysis and sections constructed from geological mapping provides a representation of velocity from selected parts of the Carboneras fault zone. First break tomography images show particularly well the location of steeply-inclined fault cores, and these correlate generally well with geological mapping and laboratory velocity measurements corrected for the effect of cracks. The decoration of the fault zone with intrusive igneous material is well correlated with the results of geological observations. Comparisons made between the field (seismic) inversion model and laboratory forward velocity model in El Saltador valley show the laboratory and field velocity measurements made within the fault zone can be reconciled by accounting for the effects of crack damage in field data.
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Vice, Garrett S. « Structural controls of the Astor Pass-Terraced Hills geothermal system in a region of strain transfer in the western Great Basin, northwestern Nevada ». abstract and full text PDF (UNR users only), 2008. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1456425.
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Rose, R. V. « Structure and metamorphism of the Haast Schist and Torlesse Zones between the Alpine Fault and the D'urville Valley, South Nelson ». Thesis, University of Canterbury. Geology, 1986. http://hdl.handle.net/10092/6703.
Texte intégralRésumé :
Within the bends region of the Alpine Fault two structural trends have been identified. These are a D1-D2 “Rangitata” trend and a D3 “Kaikoura” trend. The D1 - D2 trend maintains a northeasterly strike of both bedding and S2 schistosity which is independent of the Alpine Fault, intersecting in such a way as to verge into the Fault from the south at an acute angle. Within the Glenroy section, the relative angle changes such that this trend approaches obliquely from the north. The D3 trend overprints D2 close to the Alpine Fault and is subparallel to the fault.
Two metamorphisms (M2 and M3) are identified, M2 being associated with D2 and M3 with D3. S3 schistosity, L3 lineations and F3 folds are associated with strain in, and adjacent to the Alpine Fault Zone.
There is no direct evidence that the Haast Schists slip around and past a fixed bend in the Alpine Fault Zone. The double bend of the Alpine Fault is thus fixed with respect to the “Wairau Block” (that area between the Alpine/Wairau and Awatere Faults), and forms the leading edge of a wedge shaped body of Haast Schist and Torlesse Zone metasediments.
L3 lineations including quartz rodding, trend and plunge at approximately 060/50° northeast, and are assumed to reflect the transport direction in non-coaxial plane strain within the Alpine Fault Zone. The Haast Schists are being thrust over the Western Province with the vector direction and rate of movement of the rock mass remaining relatively constant at all points around the curve of the Alpine Fault.
Likely orientations of the XY plane of strain in the Alpine Fault Zone are discussed. It is concluded that a distinctly separate schistosity will not form unless pre-existing metamorphic layering is suitably oriented with respect to the shear zone. Consequently, transition from M2 (Rangitata Phase) schists to M3 (Alpine Fault generated) schists may be subtle and difficult to determine either in the field or in thin section.
Rotation of the D2 structural trend by ductile drag on a macroscopic scale within the Alpine Fault Zone appears to be counterclockwise. This is to be expected if (as is the case in the bends region) the early anisotropy has a more northerly strike than the convergence vector.
Equal area projection plots of post-metamorphic brittle shear surfaces cluster strongly, defining dominant shear sets oriented west-northwest to northwest and east-northeast respectively. Those shears which strike northwest exhibit minor movement of sinistral sense, whereas those striking northeast show a dextral movement. No large brittle offsets have been demonstrated, and cumulative offset on these shear systems has not altered the gross structural trends.
16
Sha'ath, N. A. H. « The structure of the Majma'ah graben complex, central Arabia ». Thesis, University of Bristol, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.372040.
Texte intégral
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Keighley, Bradbury Kelly. « Rock Properties and Structure Within the San Andreas Fault Observatory at Depth (SAFOD) Borehold, Northwest of Parkfield, California : In Situ Observations of Rock Deformation Processes and Fluid-Rock Interactions of the San Andreas Fault Zone at ~ 3 km Depth ». DigitalCommons@USU, 2012. https://digitalcommons.usu.edu/etd/1410.
Texte intégralRésumé :
This project examines the composition, structure, and geophysical properties of rocks sampled within the San Andreas Fault Observatory at Depth (SAFOD) borehole drilling experiment near Parkfield, California. Cuttings, sidewall cores, spot-core, and whole-rock core are examined from the meso- to micro-scale to characterize the nearfault environment at shallow crustal levels (0-4 km) along the central segment of the San Andreas fault. The central segment deforms by contiuous aseismic creep and microseismicity. An integrated approach utilizing core-logging, detailed structural core mapping, petrology, microstructural analyses, whole-rock geochemistry, borehole geophysics, and analog field studies is followed.
At SAFOD, fractured granitic rocks and arkosic sediments are identified west of the San Andreas fault zone on the Pacific Plate; whereas sheared fine-grained sediments, ultrafine black fault-related rocks, and serpentinite-bearing fault gouge are present within and northeast of the fault zone on the North American Plate. Here, the fault consists of a broad zone of variably damaged rock containing localized zones of highly concentrated shear that often juxtapose distinct rock-types. Two zones of serpentinite-bearing clay gouge, each meters-thick are found in two locations where active aseismic creep was identified in the borehole. The gouge is composed of Mg-rich clays, serpentinite (lizardite ± chrysotile) with notable increases in magnetite, and Fe-, Ni-, and Cr-oxides/hydroxides and Fe-sulfides relative to the surrounding host rock. Organic carbon is locally high within fractures and bounding slip surfaces. The rocks adjacent to and within the two gouge zones display a range of deformation including intensely fractured regions, blockin- matrix fabrics, and foliated cataclasite structure. The blocks and clasts predominately consist of competent sandstone and siltstone embedded in a clay-rich matrix that displays a penetrative scaly fabric. Mineral alteration, veins, fracture-surface coatings, and slickelined surfaces are present throughout the core, and reflect a long history of syndeformation and fluid-rock reaction that contributes to the low-strength and creep in the meters-thick gouge zones.
Evaluation of borehole geophysical data and elastic modulii for the lithologic and structural units identified in the SAFOD Phase 3 core reveal a correlation between composition and textures and the structural and/or permeability architecture of the SAF at SAFOD. Highly reduced velocity and elastic modulii surround the two serpentinitev bearing gouge zones, the Buzzard Canyon fault to the southwest, and another bounding fault to the northeast. Velocity and elastic moduli values on the Pacific Plate or southeast of the active fault trace intersected by SAFOD are much higher relative to the values measured on the North American Plate, or northeast of the fault trace. Within and adjacent to the two active gouge zones, the rock properties are highly variable over short distances, however, they are significantly lower relative to material outside of the fault zones.
This research contributes critical evidence for rock properties and slip behavior within an active plate boundary fault. Results from this research and the SAFOD experiment help to constrain numerous hypotheses related to fault zone behavior and earthquake generation within central California.
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Pellegrino, Alessandra Giovanna. « Understanding block rotation along strike-slip fault zones in Yunnan (China) : paleomagnetic and structural approach ». Doctoral thesis, Università di Catania, 2019. http://hdl.handle.net/10761/4133.
Texte intégralRésumé :
Data from this study report on the paleomagnetism of sedimentary and volcanic rocks cropping out near the Gaoligong and Ailao-Shan Red River Shear Zones. Fifty paleomagnetic sites were analyzed collecting 503 samples, during the first year of Ph.D., at variable distances (up to ca. 25 km) from mylonites exposed along the Gaoligong fault. Jurassic-Cretaceous red bed sites yield systematic CW rotations with respect to Eurasia reaching the peak values of 176 degree close to the fault, and progressively decrease moving eastward, up to be virtually annulled ca. 20 km E of mylonite contact. West of the Gaoligong fault, Pliocene-Holocene sites from the Tengchong volcanic field do not rotate. Thus, data show that the Gaoligong Shear Zone activity yielded significant CW rotations that were likely coeval to the main Eocene-Miocene episodes of dextral fault shear. The Gaoligong zone rotation pattern conforms to a quasi-continuous crust kinematic model, and shows blocks of less then or equal 1 km size close to the fault, which become bigger moving eastward. Rotation and width values of the rotated-deformed zone translate to a 230-290 km Gaoligong Shear Zone dextral offset, which shows that fault shear plays a significant role in Indochina CW block rotation.During the second year of Ph.D., forty-four Triassic-Cretaceous sites (425 samples) were collected at both sides of the Ailao-Shan Red River Shear Zone (ARRSZ), within the Chuandian, Lanping and Northern Simao blocks. Nearly all sites yielded measurable and stable magnetization components, but magnetization acquisition timing was different in the three blocks. Sites from the Chuandian block show a normal polarity and were remagnetized after folding. In the northern Simao block the magnetization was acquired before folding (about 33 Ma ago), but the ubiquitous normal polarity in Jurassic-Cretaceous sites suggests a pre-folding magnetic overprint. The data show variable and different rotation that do not display evidence of a rigid block rotation, but suggest that the northern Simao block is made of small (few km size) sub-blocks rotating CW, separated by non-rotating domains of similar size. Finally, a high-temperature (640-680 degree C) magnetization component suggests a similar rotational behaviour (CW-rotating and non-rotating sub-blocks) in the centre of the Lanping block. Conversely, a 300-640 degree C component was later acquired at 28% unfolding and subsequently underwent no rotation. The sites close (less than 25 km) to the ARRSZ yield great rotations of nearly 180 degree, which confirm past occurrence of significant strike-slip shear along the ARRSZ itself. Conversely, sites located at 10-15 km distance from the Chongshan Shear Zone show ca. 90 degree CCW rotations that imply a left-lateral shear along the fault zone, consistently with recent geological evidence. Summarizing, data from my Ph.D. study, together with previous evidence of rotations documented both near the fault zones and within the blocks themselves, show that crustal deformation of the Yunnan is extremely complex and still puzzling. The Baoshan and Lanping-Simao blocks underwent strong internal deformation and were likely fragmented in smaller independent sub-blocks whose kinematics and tectonics are still a matter of speculation.
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Kanaya, Takamasa. « Structure and kinematics of the Suzume fault, Okitsu melange, Shimanto accretionary complex, Japan ». Texas A&M University, 2006. http://hdl.handle.net/1969.1/4758.
Texte intégralRésumé :
The Okitsu mélange in the Shimanto accretionary complex, the onshore extension of
the modern Nankai accretionary prism, consists of a kilometer-size duplex of oceanic
basalt and trench-fill sedimentary rocks, and is thought to represent rocks underplated to
the prism along the subduction plate-boundary at seismogenic depth. An internal, horsebounding
thrust of the duplex, referred to as the Suzume fault, juxtaposes basalt in the
hanging wall and sedimentary rocks in the footwall. Structure and fabric of the fault was
characterized at the mesoscale to investigate the processes and structural evolution along
a plate-boundary décollement. The fault zone in the hanging wall consists of decimeterthick
ultracataclasite bounded by a several m thick zone of fractured basalt, and likely
records 2+ km displacement along the thrust. The footwall consists of decimeter-thick
ultracataclasite bounded by a 20-m-thick zone of ductile shear in flattened sedimentary
host rock, and likely records 30+ km of displacement. The asymmetric structure across
the Suzume fault, as well as inferred displacement fields and timing relations, are
consistent with a tectonic model in which the footwall records early ductile, compactive
deformation of poorly consolidated sediments during underthrusting at the prism toe
region, followed by extremely localized cataclasis at the underplating depth. In contrast,
the hanging wall is deformed by intense cataclasis, and only during underplating.
Deformation style and strain state in the footwall of the Suzume fault is qualitatively
similar to the modern Costa Rica underthrust section at the toe region. Similarity in the
structure and fabric of the hanging wall between the Suzume fault and modern
décollement zones sampled through scientific drilling suggests that intense cataclasis
under horizontal contraction likely is a common feature for the hanging wall of the décollement zone throughout the toe to underplating regions. Structures in the Suzume
fault that are not in common with the modern décollements imply progressive
consolidation during underthrusting from the toe to underplating depths may be
responsible for the localization of shear in the footwall. At several kilometers depth,
displacement along the plate boundary is likely accommodated within an extremely
narrow zone as recorded in the ultracataclasite of the Suzume fault.
20
Wilson, Paul. « Structural geology, tectonic history and fault zone microstructures of the Upper palaeozoic Maritimes Basin, southern New Brunswick ». Restricted access (UM), 2006. http://libraries.maine.edu/gateway/oroauth.asp?file=orono/etheses/37803141.pdf.
Texte intégralRésumé :
Thesis (Ph.D.) -- University of New Brunswick, Dept. of Geology, 2006.Title from PDF title page (viewed on May 25, 2010) Available through UMI ProQuest Digital Dissertations. Includes bibliographical references (leaves 299-321). Also issued in print.
21
Duffy, Brendan Gilbert. « Development of Multichannel Analysis of Surface Waves (MASW) for Characterising the Internal Structure of Active Fault Zones as a Predictive Method of Identifying the Distribution of Ground Deformation ». Thesis, University of Canterbury. Geological Sciences, 2008. http://hdl.handle.net/10092/2051.
Texte intégralRésumé :
Bulk rock strength is greatly dependent on fracture density, so that reductions in rock strength associated with faulting and fracturing should be reflected by reduced shear coupling and hence S-wave velocity. This study is carried out along the Canterbury rangefront and in Otago. Both lie within the broader plate boundary deformation zone in the South Island of New Zealand. Therefore built structures are often, , located in areas where there are undetected or poorly defined faults with associated rock strength reduction. Where structures are sited near to, or across, such faults or fault-zones, they may sustain both shaking and ground deformation damage during an earthquake. Within this zone, management of seismic hazards needs to be based on accurate identification of the potential fault damage zone including the likely width of off-plane deformation. Lateral S-wave velocity variability provides one method of imaging and locating damage zones and off-plane deformation. This research demonstrates the utility of Multi-Channel Analysis of Surface Waves (MASW) to aid land-use planning in such fault-prone settings. Fundamentally, MASW uses surface wave dispersive characteristics to model a near surface profile of S-wave velocity variability as a proxy for bulk rock strength. The technique can aid fault-zone planning not only by locating and defining the extent of fault-zones, but also by defining within-zone variability that is readily correlated with measurable rock properties applicable to both foundation design and the distribution of surface deformation. The calibration sites presented here have well defined field relationships and known fault-zone exposure close to potential MASW survey sites. They were selected to represent a range of progressively softer lithologies from intact and fractured Torlesse Group basement hard rock (Dalethorpe) through softer Tertiary cover sediments (Boby’s Creek) and Quaternary gravels. This facilitated initial calibration of fracture intensity at a high-velocity-contrast site followed by exploration of the limits of shear zone resolution at lower velocity contrasts. Site models were constructed in AutoCAD in order to demonstrate spatial correlations between S-wave velocity and fault zone features. Site geology was incorporated in the models, along with geomorphology, river profiles, scanline locations and crosshole velocity measurement locations. Spatial data were recorded using a total-station survey. The interpreted MASW survey results are presented as two dimensional snapshot cross-sections of the three dimensional calibration-site models. These show strong correlations between MASW survey velocities and site geology, geomorphology, fluvial profiles and geotechnical parameters and observations. Correlations are particularly pronounced where high velocity contrasts exist, whilst weaker correlations are demonstrated in softer lithologies. Geomorphic correlations suggest that off-plane deformation can be imaged and interpreted in the presence of suitable topographic survey data. A promising new approach to in situ and laboratory soft-rock material and mass characterisation is also presented using a Ramset nail gun. Geotechnical investigations typically involve outcrop and laboratory scale determination of rock mass and material properties such as fracture density and unconfined compressive strength (UCS). This multi-scale approach is espoused by this study, with geotechnical and S-wave velocity data presented at multiple scales, from survey scale sonic velocity measurements, through outcrop scale scanline and crosshole sonic velocity measurements to laboratory scale property determination and sonic velocity measurements. S-wave velocities invariably increased with decreasing scale. These scaling relationships and strategies for dealing with them are investigated and presented. Finally, the MASW technique is applied to a concealed fault on the Taieri Ridge in Macraes Flat, Central Otago. Here, high velocity Otago Schist is faulted against low velocity sheared Tertiary and Quaternary sediments. This site highlights the structural sensitivity of the technique by apparently constraining the location of the principal fault, which had been ambiguous after standard processing of the seismic reflection data. Processing of the Taieri Ridge dataset has further led to the proposal of a novel surface wave imaging technique termed Swept Frequency Imaging (SFI). This inchoate technique apparently images the detailed structure of the fault-zone, and is in agreement with the conventionally-determined fault location and an existing partial trench. Overall, the results are promising and are expected to be supported by further trenching in the near future.
22
Strane, Michael D. Oskin Michael. « Slip rate and structure of the nascent Lenwood fault zone, Eastern California ». Chapel Hill, N.C. : University of North Carolina at Chapel Hill, 2007. http://dc.lib.unc.edu/u?/etd,1336.
Texte intégralRésumé :
Thesis (M.S.)--University of North Carolina at Chapel Hill, 2007.Title from electronic title page (viewed Apr. 25, 2008). "... in partial fulfillment of the requirements for the degree of Master of Sciences in the Department of Geological Sciences." Discipline: Geology; Department/School: Geological Sciences.
23
Mizuno, Takashi. « Deep Structure of Active Faults Estimated from Subsurface Observation of Fault-Zone Trapped Waves - the Nojima and the Mozumi-Sukenobu faults, Japan ». 京都大学 (Kyoto University), 2003. http://hdl.handle.net/2433/149077.
Texte intégralRésumé :
Kyoto University (京都大学)0048
新制・課程博士
博士(理学)
甲第9955号
理博第2616号
新制||理||1334(附属図書館)
UT51-2003-H376
京都大学大学院理学研究科地球惑星科学専攻
(主査)助教授 西上 欽也, 教授 Mori James J., 教授 岡田 篤正
学位規則第4条第1項該当
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Alfvén, Linda. « Structural and Engineering Geological Investigation of Fracture Zones and Their Effect on Tunnel Construction ». Thesis, Uppsala universitet, Institutionen för geovetenskaper, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-272495.
Texte intégralRésumé :
This thesis project was conducted in connection with the project, Stockholm’s future sewer pipeline, which is a planned sewer pipe that will run through a tunnel from western to southern Stockholm. This tunnel will pass under Lake Mälaren between Eolshäll and Smedslätten, where there are two faults indicated on the geological map, that could affect the tunnelling and create risks during the construction. Geophysical- and water-loss measurements along with core drilling have been carried out in the area. The objectives of this thesis are to create a structural and engineering geological understanding of the passage beneath Lake Mälaren based on drill core mapping, field work, data from previous investi-gations and 2D-models of the tunnel excavation both within and outside the indicated fault zone. The core mapping supports the existence of one fault zone, which is indicated on the geological map supported by water-losses at several places along the drill core as well as core losses. Field work indi-cated the existence of a conjugate fracture sets.The 2D-models present plastic behaviour of the rock in the fault zone as the worst case scenario during excavation with the highest deformation displacement. The excavation procedure and the tunnel form also play a significant role. Since this thesis highlights some significant risks and problems that can occur during tunnelling, its findings may be useful during the tunnel construction.Denna uppsats är skriven med koppling till projektet, Stockholms framtida avloppsledning, vilket inkluderar en ny tunnel för transport av avloppsvatten från västra till södra Stockholm. Tunneln kommer att passera under Mälaren mellan Smedslätten och Eolshäll, där det är två förkastningar indikerade på geologiska kartor som kan orsaka stora risker för byggnationen av tunneln. Geofysiska mätningar, kärnborrning och vattenförlustmätning har tidigare utförts i området. Målen för denna uppsats är att skapa en geologisk- och bergmekanisk förståelse för tunnelpassagen under Mälaren utifrån kärnkartering, fältarbete, data från tidigare undersökningar och 2D-modeller av tunneluttag i den indikerade zonen och utanför. Kärnkarteringen stödjer existensen av en förkastningszon som finns på den geologiska kartan. Flertalet vattenförluster är indikerade längs med hela kärnan tillsammans med en del förekomster av kärnförluster. Fältarbetet indikerar på förekomst av ett konjugerande sprickset. 2D-modeller över tunneln visade att olika egenskaper på berget samt hur uttaget av tunneln sker har betydelse för deformationernas storlek. Den här uppsatsen belyser några viktiga problem och risker som kan uppstå under tunnelbyggnationen, dessa upptäckter kan därför vara användbara och värdefulla under hela byggnationen.
25
Toy, Virginia Gail, et n/a. « Rheology of the Alpine Fault Mylonite Zone : deformation processes at and below the base of the seismogenic zone in a major plate boundary structure ». University of Otago. Department of Geology, 2008. http://adt.otago.ac.nz./public/adt-NZDU20080305.110949.
Texte intégralRésumé :
The Alpine Fault is the major structure of the Pacific-Australian plate boundary through New Zealand�s South Island. During dextral reverse fault slip, a <5 million year old, ~1 km thick mylonite zone has been exhumed in the hanging-wall, providing unique exposure of material deformed to very high strains at deep crustal levels under boundary conditions constrained by present-day plate motions. The purpose of this study was to investigate the fault zone rheology and mechanisms of strain localisation, to obtain further information about how the structural development of this shear zone relates to the kinematic and thermal boundary constraints, and to investigate the mechanisms by which the viscously deforming mylonite zone is linked to the brittle structure, that fails episodically causing large earthquakes.
This study has focussed on the central section of the fault from Harihari to Fox Glacier. In this area, mylonites derived from a quartzofeldspathic Alpine Schist protolith are most common, but slivers of Western Province-derived footwall material, which can be differentiated using mineralogy and bulk rock geochemistry, were also incorporated into the fault zone. These footwall-derived mylonites are increasingly common towards the north.
At amphibolite-facies conditions mylonitic deformation was localised to the mylonite and ultramylonite subzones of the schist-derived mylonites. Most deformation was accommodated by dislocation creep of quartz, which developed strong Y-maximum crystallographic preferred orientation (CPO) patterns by prism (a) dominant slip. Formation of this highly-oriented fabric would have led to significant geometric softening and enhanced strain localisation. During this high strain deformation, pre-existing Alpine Schist fabrics in polyphase rocks were reconstituted to relatively well-mixed, finer-grained aggregates. As a result of this fabric homogenisation, strong syn-mylonitic object lineations were not formed. Strain models show that weak lineations trending towards ~090� and kinematic directions indicated by asymmetric fabrics and CPO pattern symmetry could have formed during pure shear stretches up-dip of the fault of ~3.5, coupled with simple shear strains [greater than or equal to]30. The preferred estimate of simple:pure shear strain gives a kinematc vorticity number, W[k] [greater than or equal to]̲ 0.9997.
Rapid exhumation due to fault slip resulted in advection of crustal isotherms. New thermobarometric and fluid inclusion analyses from fault zone materials allow the thermal gradient along an uplift path in the fault rocks to be more precisely defined than previously. Fluid inclusion data indicate temperatures of 325+̲15�C were experienced at depths of ~45 km, so that a high thermal gradient of ~75�C km⁻� is indicated in the near-surface. This gradient must fall off to [ less than approximately]l0�C km⁻� below the brittle-viscous transition since feldspar thermobarometry, Ti-inbiotite thermometry and the absence of prism(c)-slip quartz CPO fabrics indicate deformation temperatures did not exceed ~ 650�C at [greater than or equal to] 7.0-8.5�1.5 kbar, ie. 26-33 km depth.
During exhumation, the strongly oriented quartzite fabrics were not favourably oriented for activation of the lower temperature basal(a) slip system, which should have dominated at depths [less than approximately]20 km. Quartz continued to deform by crystal-plastic mechanisms to shallow levels. However, pure dislocation creep of quartz was replaced by a frictional-viscous deformation mechanism of sliding on weak mica basal planes coupled with dislocation creep of quartz. Such frictional-viscous flow is particularly favoured during high-strain rate events as might be expected during rupture of the overlying brittle fault zone. Maximum flow stresses supported by this mechanism are ~65 Mpa, similar to those indicated by recrystallised grain size paleopiezometry of quartz (D>25[mu]m, indicating [Delta][sigma][max] ~55 MPa for most mylonites). It is likely that the preferentially oriented prism (a) slip system was activated during these events, so the Y-maximum CPO fabrics were preserved. Simple numerical models show that activation of this slip system is favoured over the basal (a) system, which has a lower critical resolved shear stress (CRSS) at low temperatures, for aggregates with strong Y-maximum orientations. Absence of pervasive crystal-plastic deformation of micas and feldspars during activation of this mechanism also resulted in preservation of mineral chemistries from the highest grades of mylonitic deformation (ie. amphibolite-facies).
Retrograde, epidote-amphibolite to greenschist-facies mineral assemblages were pervasively developed in ultramylonites and cataclasites immediately adjacent to the fault core and in footwall-derived mylonites, perhaps during episodic transfer of this material into and subsequently out of the cooler footwall block. In the more distal protomylonites, retrograde assemblages were locally developed along shear bands that also accommodated most of the mylonitic deformation in these rocks. Ti-in-biotite thermometry suggests biotite in these shear bands equilibrated down to ~500+̲50�C, suggesting crystal-plastic deformation of this mineral continued to these temperatures. Crossed-girdle quartz CPO fabrics were formed in these protomylonites by basal (a) dominant slip, indicating a strongly oriented fabric had not previously formed at depth due to the relatively small strains, and that dislocation creep of quartz continued at depths [less than or equal to]20 km. Lineation orientations, CPO fabric symmetry and shear-band fabrics in these protomylonites are consistent with a smaller simple:pure shear strain ratio than that observed closer to the fault core (W[k] [greater than approximately] 0.98), but require a similar total pure shear component. Furthermore, they indicate an increase in the simple shear component with time, consistent with incorporation of new hanging-wall material into the fault zone. Pre-existing lineations were only slowly rotated into coincidence with the mylonitic simple shear direction in the shear bands since they lay close to the simple shear plane, and inherited orientations were not destroyed until large finite strains (<100) were achieved.
As the fault rocks were exhumed through the brittle-viscous transition, they experienced localised brittle shear failures. These small-scale seismic events formed friction melts (ie. pseudotachylytes). The volume of pseudotachylyte produced is related to host rock mineralogy (more melt in host rocks containing hydrated minerals), and fabric (more melt in isotropic host rocks). Frictional melting also occurred within cataclastic hosts, indicating the cataclasites around the principal slip surface of the Alpine Fault were produced by multiple episodes of discrete shear rather than distributed cataclastic flow. Pseudotachylytes were also formed in the presence of fluids, suggesting relatively high fault gouge permeabilities were transiently attained, probably during large earthquakes. Frictional melting contributed to formation of phyllosilicate-rich fault gouges, weakening the brittle structure and promoting slip localisation. The location of faulting and pseudotachylyte formation, and the strength of the fault in the brittle regime were strongly influenced by cyclic hydrothermal cementation processes.
A thermomechanical model of the central Alpine Fault zone has been defined using the results of this study. The mylonites represent a localised zone of high simple shear strain, embedded in a crustal block that underwent bulk pure shear. The boundaries of the simple shear zone moved into the surrounding material with time. This means that the exhumed sequence does not represent a simple 'time slice' illustrating progressive fault rock development during increasing simple shear strains. The deformation history of the mylonites at deep crustal P-T conditions had a profound influence on subsequent deformation mechanisms and fabric development during exhumation.
26
Taylor, Tatia R. « ORIGIN AND STRUCTURE OF THE POVERTY HILLS, OWENS VALLEY FAULT ZONE, OWENS VALLEY, CALIFORNIA ». Miami University / OhioLINK, 2002. http://rave.ohiolink.edu/etdc/view?acc_num=miami1021990715.
Texte intégral
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Lefèvre, Mélody. « Propriétés structurales, pétro-physiques et circulations de fluides au sein d'une zone de failles dans les argiles ». Thesis, Aix-Marseille, 2016. http://www.theses.fr/2016AIXM4320/document.
Texte intégralRésumé :
Les zones de failles concentrent la migration de fluides et la déformation dans la croûte supérieure. Les propriétés hydrauliques des formations argileuses en font des excellents sites de stockage et des roches mères performants. Les zones de failles peuvent jouer deux rôles contraires dans la circulation de fluides, soit elles s’expriment sous forme de drains, soit elles constituent une barrière, et souvent les deux rôles sont combinés au sein d’une même zone de failles. Les processus de migration des fluides dans les zones de failles affectant les argiles sont peu connus. Cette étude s’est focalisée sur la structure, les paléo-circulations, les circulations actuelles lors de tests d’injection et les propriétés pétro-physiques de la zone de failles présente dans le laboratoire de recherche souterrain de Tournemire dans les argilites Toarciennes. La structure de la zone de failles a été caractérisée par des forages et reconstituée en 3D par modélisation numérique, permettant de définir des faciès de déformation. L’architecture de la zone de failles se caractérise par une imbrication de facies de déformations plus ou moins intenses sans claire organisation en cœur et zone endommagée comme observée dans les roches plus dures. Les zones intactes, fracturées et les brèches sont respectivement caractérisées par des porosités matricielles comprises entre 9.5-13.5, 10-15 et 13-21%. La circulation de fluide se concentrant aux limites de la brèche et au niveau des zones de failles «immatures» ou secondaires comprises dans les zones fracturées. Lors de son activité, la zone de failles a déjà été affectée par au moins deux phases de circulations de fluidesFault zones concentrate fluids migration and deformations in the upper crust. The shale hydraulic properties make them excellent storage sites and hydrocarbon reservoirs/source rocks. Fault zones can play two roles in the fluid circulation; drains or barriers, in general, both roles are combined within the same fault zone. What are the conditions that promote the fluid circulation along the fault zones in shales and what are the fault zone impacts on the formation properties are relatively poorly explored key questions. This study focused on characterizing the relationships between fault architecture, paleo-fluid as well as current fluid circulations through the analysis of fault calcite mineralization, injection tests and petrophysical properties conducted on a fault zone outcropping underground in the Tournemire research laboratory nested in the Toarcian shale. The fault zone structure was characterized using boreholes data and reconstructed in 3D through modeling to define different deformation facies. No clear facies organization is observed, a fault core and a fault damage zone being difficult to define as it is in hard rocks. The intact, fractured and breccia facies are characterized by a porosity of 9.5-13.5, 10-15 and 13-21%. Large fluid flowrate concentrated along a few “channels” located at the breccia boundaries and in the secondary fault zones that displayed fractured facies and limited breccia fillings. Detailed microstructural and geochemical analysis at the breccia/fractured zones interface revealed that fluids circulated out of the main shear zones, in micro-more or less inherited fractures highlighting a decoupling between fault slip and fluid migrations
28
Hayman, Nicholas W. « Structure and petrology of gouge and breccia bearing shallow crustal shear zones of detachment faults in Death Valley, California / ». Thesis, Connect to this title online ; UW restricted, 2005. http://hdl.handle.net/1773/6699.
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Haddox, David A. « Mapping and Kinematic Structural Analysis of the Deep Creek Fault Zone, South Flank of the Uinta Mountains, Near Vernal, Utah ». Diss., CLICK HERE for online access, 2005. http://contentdm.lib.byu.edu/ETD/image/etd819.pdf.
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Cowan, Hugh Allister. « Structure, seismicity and tectonics of the Porter's Pass-Amberley fault zone, North Canterbury, New Zealand ». Thesis, University of Canterbury. Geology, 1992. http://hdl.handle.net/10092/4703.
Texte intégralRésumé :
The Porter's Pass-Amberley Fault Zone (PPAFZ) is a complex zone of anastomosing faults and folds bounding the south-eastern edge of the transition from subducting Pacific Plate to continental collision on the Australia Plate boundary. This study combines mapping of a 2000 km2 zone from the Southern Alps northeast to the coast near Amberley, 40 km north of metropolitan Christchurch, with an analysis of seismicity and a revision of regional seismic hazard.
Three structural styles: 1) a western strike-slip, and 2) a more easterly thrust and reverse domain, pass into 3) a northwest verging fold belt on the northern Canterbury Plains, reflecting the structural levels exposed and the evolving west to east propagation. Basal remnants of a Late Cretaceous-Cenozoic, largely marine sedimentary cover sequence are preserved as outliers that unconformably overlie Mesozoic basement (greywacke and argillite of the Torlesse terrain) in the mountains of the
PPAFZ and are underlain by a deeply leached zone which is widely preserved. Structure contouring of the unconformity surface indicates maximum, differential uplift of c.2600 m in the southwest, decreasing to c.1200 m in the coastal fold belt to the northeast. Much lower rates (or reversal) of uplift are evident a few kilometres southeast of the PPAFZ range-front escarpment.
The youngest elements of the cover sequence are basement-derived conglomerates of Plio-Pleistocene age preserved on the SE margin. The source is more distant than the intervening mountains of the PPAFZ, probably from the Southern Alps, to the west and northwest. The absence of another regional unconformity on Mesozoic basement, older than Pleistocene, indicates that this uplift is post-Pliocene. Late Pleistocene(<100 kyr) differential uplift rates of c.0.5-2.7 m/kyr from uplifted marine terraces at the east coast, and rates of 2.5-3.3 m/kyr for tectonically-induced river-down cutting further west, suggest that uplift commenced locally during the last 1 Ma, and possibly within the last 0.5 Ma, if average rates are assumed to be uniform over time.
Analysis of seismicity, recorded during a 10 week regional survey of micro earthquakes in 1990, identified two seismic zones beneath North Canterbury: 1) a sub-horizontal zone of activity restricted to the upper crust (≤12 km); and 2) a seismic zone in the lower crust (below a ceiling of ≤17 km), that broadens vertically to the north and northwest to a depth of c.40 km, with a bottom edge which dips 10°N and 15°NW, respectively. No events were recorded at depths between 12 km and 17 km, which is interpreted as a relatively aseismic, mid-crustal ductile layer.
Marked differences (up to 60°) in the trend of strain axes for events above and below the inferred ductile layer are observed only north of the PPAFZ. A fundamental, north-to-south increase in the
Wave-length of major geological structures occurs across the PPAFZ, and is interpreted as evidence that the upper crust beneath the Canterbury Plains is coupled to the lower crust, whereas the upper crust further north is not. Most of the recorded micro earthquakes <12 km deep beneath the PPAFZ have strike-slip mechanisms. It is probable that faults splay upward into the thrusts and folds at the surface as an evolving transpression zone in response to deep shear in basement.
There have been no historic surface ruptures of the PPAFZ, but the zone has been characterised historically by frequent small earthquakes. Paleoseismic data (dated landslides and surface ruptures) compiled in this study, indicate a return period of 1500-1900 years between the last two M>7-7.5 earthquakes, and 500-700 years have elapsed since the last. The magnitudes of these events are estimated at c.M7.5, which represents a probable maximum magnitude for the PPAFZ. There are insufficient data to determine whether or not the frequency of large earthquakes conforms to a recognised model of behaviour, but comparison of the paleoseismic data with the historic record of smaller earthquakes, suggests that the magnitudes of the largest earthquakes in this zone are not exponentially distributed. A seismicity model for the PPAFZ (Elder et al., 1991) is reviewed, and a
b-value of 1.0 is found to be consistent with the newly acquired paleoseismic data. This b-value reduces the predicted frequency of large earthquakes (M≥7.0) in this zone by a factor of 3.5, while retaining a conservative margin that allows for temporal variations in the frequency of large events and the possibility that the geological database is incomplete, suggesting grounds for revising the hazard model for Christchurch.
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Brehme, Maren [Verfasser], Martin [Akademischer Betreuer] Sauter et Günter [Akademischer Betreuer] Zimmermann. « The role of fault zones on structure, operation and prospects of geothermal reservoirs - A case study in Lahendong, Indonesia / Maren Brehme. Gutachter : Martin Sauter ; Günter Zimmermann. Betreuer : Martin Sauter ». Göttingen : Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2015. http://d-nb.info/1071713442/34.
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Dempsey, Edward Damien. « The kinematics, rheology, structure and anisotropy of the Alpine schist derived Alpine fault zone mylonites, New Zealand ». Thesis, University of Liverpool, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.539562.
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Cook, Becky J. « Along and across strike variations in the structure, material and fault properties of the Sumatran Subduction Zone ». Thesis, University of Southampton, 2014. https://eprints.soton.ac.uk/374820/.
Texte intégralRésumé :
Earthquake ruptures offshore of north-central Sumatra in 2004 (Sumatra-Andaman segment) and 2005 (Nias segment) exhibited variable shallow slip behaviour that is well resolved by tsunami, seismologic, and geodetic observations. Closely spaced 2D MCS profiles collected covering these rupture segments, the segment to the south (Mentawai segment), and the segment boundaries allow an unprecedented opportunity to study the detailed along- and across-strike variation in the structure and properties of the wedge and plate boundary that may be related to the variable shallow slip behaviour. The large tsunami generated by the 2004 earthquake is thought to have been the result of unexpected shallow slip on the shallow plate boundary of the southern Sumatra-Andaman segment; whereas in the Nias segment the shallow plate boundary showed evidence of significant afterslip and the 2005 earthquake did not generate a significant tsunami. In the northern Mentawai segment, Batu Segment Boundary Zone, and southern Nias segment the shallow plate boundary is relatively weak and the weakened plate boundary is likely related to dehydration reaction occurring below the frontal prism and potential fluid flow focussing on basement topographic highs. In these areas, imbricate faulting in the frontal prism occurs along landward and/or seaward dipping faults. At the mid-slope break, the slip rate along these imbricate faults, formed in the frontal prism, decreases and they are potentially crosscut by out-of-sequence faults. In the southern Sumatra-Andaman segment, our findings of a relatively strong plate boundary fault are consistent with increased compaction and early dehydration of material within the thick incoming section which strengthens the incoming section and results in a potentially seismogenic shallow plate boundary. The accretionary prism here is characterised by an unusual prism profile with a narrow steep toe and broad flat plateau. We propose that the steep prism toe is built up by coeval faulting on both seaward and landward dipping faults. At the break in slope, underplating becomes the dominant prism and the transition from frontal accretion to underplating contributes to the development of the unusual prism geometry. Within our study area, we find that there is significant variability in the frictional strength of the shallow plate boundary and mechanisms of accretion, which can be correlated with the geometry and faulting within the prism. We show that these changes are related to a combination of subducting plate topography, trench sedimentation rates, overall sediment thickness and sediment/fault permeability.
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Taikulakov, Yerlan Yengelsbekovich. « Subsurface Structure Of The Central Thrace Basin From 3d Seismic Reflection Data ». Master's thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12612894/index.pdf.
Texte intégralRésumé :
The Thrace Basin located in northwest Turkey displays attractive prospective traps for hydrocarbon and has received much attention from the petroleum industry. Despite the extensive exploration efforts, there are only few studies which address the fault kinematics and deformation mechanism of the
region in connection with structural development. In this study, 3D raw seismic data set collected around Temrez High near Babaeski fault zone will be processed and interpreted along with the available borehole data to reveal the subsurface structure of the region that will contribute towards understanding the Neogene tectonic evolution of the central Thrace basin, origin of the transcurrent tectonics and possible role of the North Anatolian Fault Zone.
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Hislop, Ann. « FAULT EVOLUTION IN THE NORTHWEST LITTLE SAN BERNARDINO MOUNTAINS, SOUTHERN CALIFORNIA : A REFLECTION OF TECTONIC LINKAGE BETWEEN THE SAN ANDREAS FAULT AND THE EASTERN CALIFORNIA SHEAR ZONE ». UKnowledge, 2019. https://uknowledge.uky.edu/ees_etds/63.
Texte intégralRésumé :
The Little San Bernardino Mountains (LSBM) Fault Set are N-S dextral faults, east of the restraining bend of the San Andreas Fault (SAF) in southern California, that may form a tectonic linkage between the SAF and the Eastern California Shear Zone. The NW LSBM are a complexly deformed structural domain characterized by the young N-S dextral faults and older NW-oriented Dillon Shear Zone faults. Before the 1992 Joshua Tree (Mw 6.1) and Landers (Mw 7.3) earthquakes, the rugged NW LSBM was the subject of few geologic studies. This bedrock mapping study has further delineated the geometry, distribution, and relative chronology of brittle structures. A 2015 NCALM award of 51 km2 of lidar imagery on Eureka Peak Fault was used to correct fault locations.
Bedrock mapping in the epicentral areas of the 1992 Joshua Tree earthquake on Eureka Peak Fault and Landers aftershocks (Mw 5.7, 5.8) focused on the brittle structures of the evolving fault systems and potential connections with historic seismicity. The N-S dextral fault offsets from west to east are; Long Canyon (470 m), Wide Canyon (~150- 340 m), Eureka Peak (~ 225 m), California Riding Trail (850-965 m) and Deerhorn (105 m) faults with a cumulative offset of approximately 2 km. Dolomitic marble, clinopyroxene-hornblende skarn, garnet-epidote skarn and gabbro-diorite intruded by monzogranite are key lithologies used in determining offsets. Joshua Tree Fault, defined by seismicity by Kaven and Pollard (2013) is supported by additional mapped fault data. A “new” fault (Black Rock Canyon) links Wide Canyon and northern Eureka Peak faults. The distribution of aftershock seismicity plotted by depth and latitude along the N-S faults, a prominent broad seismicity trend and bedrock mapping are all consistent with interpreting the N-S faults as an incipient set of faults developing upward from a deeper through-going crustal shear zone. The seismicity since the onset of the Joshua Tree- Landers earthquake sequence on April 23, 1992, forms two distinct trends. Temporally these two trends occurred in sequence; first a N-propagating trend April 23- mid-June along Joshua Tree Fault from the Joshua Tree earthquake epicenter to north of the Pinto Mountain Fault, and secondly a prominent SE trend of Landers aftershocks (including Mw 5.7, 5.8) June 28 onwards, from the Landers earthquake epicenter, along Eureka Peak Fault to the SAF.
AFT and (U-Th)/He thermochronology indicate an abrupt boundary on Long Canyon Fault between rapid uplift within ~ 12 km of the SAF and slower uplift more than 12 km north. This boundary is projected along the Dillon Shear Zone structural grain to the 1992 Joshua Tree earthquake epicenter on southern Eureka Peak Fault, dividing the N-striking faults into northern and southern domains. The 14.7 km hypocentral depth of the Joshua Tree earthquake coincides roughly with the depth of the NE dipping SAF intersection with Eureka Peak Fault, forming a hypothesized flower structure which is consistent with rapid uplift of the LSBM escarpment near the SAF.
The LSBM Fault Set may be initiated by the upward migration of a through-going mid-crustal break and eastern migration of the current SAF trace bypassing the Big Bend slip impediment. Eureka Peak Fault with a slip rate of 10-20 mm/yr, is the proposed structure tectonically linking the SAF and the Eastern California Shear Zone.
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Aubert, Irène. « Fault zone structural and diagenetic evolution in carbonates : impact on reservoir properties (urgonian case study, SE France) ». Thesis, Aix-Marseille, 2020. http://www.theses.fr/2020AIXM0175.
Texte intégralRésumé :
Les zones de failles ont un impact important sur les réservoirs carbonatés car elles peuvent agir comme des drains ou des barrières en fonction de leurs propriétés structurales et diagénétiques. Il est important de bien comprendre ces propriétés pour déterminer les caractéristiques hydrauliques des zones de failles. Pour cela, l'approche multidisciplinaire de cette thèse combinant l’analyse structurale, diagénétique et géochimique vise à (1) contraindre l'évolution structurale et diagénétique des zones de failles dans les carbonates, (2) établir des règles et des concepts géométriques permettant de construire des modèles géologiques cohérents, et (3) permettre une meilleure compréhension de la réponse dynamique hydraulique des zones de failles dans les carbonates à travers leurs évolutions. Nous avons étudié 3 zones de failles (Castellas, D19) affectant les carbonates de plate-forme du Barrémien inférieur (faciès Urgonien) situées dans l'anticlinal de La Fare et dans celui de la Nerthe (Provence - SE France). Ces travaux ont permis de restaurer les séquences diagénétiques des zones de failles avec des analyses de ciment sous catholuminescence et des mesures des isotopes 13C et 18O. L'analyse structurale a permis de compléter l'évolution diagénétique en déterminant les caractéristiques architecturales liées à chaque activité de faille et en discriminant l'effet des structures préexistantes sur le développement ultérieur de ces dernières. Enfin, cette étude a permis d'améliorer notre compréhension du comportement hydraulique des zones de failles dans les carbonates au cours tempsFault zones strongly impact carbonates reservoir properties as they can act as drains or barriers depending of their structural and diagenetic properties. Hence, it is important to have an integrativecomprehension of these properties that affect the fault zones hydraulic properties. To this end, the multidisciplinary approach of this thesis combining structural, diagenetic and geochemical approaches aims to (1) constrain the structural and diagenetic evolution of fault zones in carbonates (2) draw rules and geometrical concepts allowing building of coherent geological models, and (3) allow a better understanding of the hydraulic dynamic response of fault zones in carbonates through their evolutions. We studied 3 fault zones (Castellas, D19) affecting lower Barremian platform carbonates (Urgonian facies) located in La Fare and Nerthe anticlines (Provence – SE France). This work allowed the restoration of fault zones diagenetic sequences with cement analyses under catholuminescence and 13C and 18O isotopes. The structural analysis completed the diagenetic evolution by determining the architectural characteristics related to each fault activity and discriminating the effect of pre-existing structures on subsequent fault development. Finally, this study improved our understanding of fault zones hydraulic behaviour in carbonates through times
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Cossette, Élise. « Crustal Seismic Anisotropy and Structure from Textural and Seismic Investigations in the Cycladic Region, Greece ». Thesis, Université d'Ottawa / University of Ottawa, 2015. http://hdl.handle.net/10393/32475.
Texte intégralRésumé :
In the first article, the seismic properties for a suite of rocks along the West Cycladic Detachment System (Greece) are calculated, using Electron backscatter diffraction (EBSD) measurements and the minerals’ elastic stiffness tensors. Muscovite and glaucophane well defined crystallographic preferred orientation increases the seismic anisotropy. Maximum Pwave velocities have the same orientation as the Miocene extension and maximum S-wave anisotropy is subhorizontal, parallel with mineral alignment, suggesting strong radial anisotropy with a slow subvertical axis of symmetry. In the second article, teleseismic receiver functions are calculated for an array of stations in the Cyclades and decomposed into back-azimuth harmonics to visualise the variations in structure and anisotropy across the array. Synthetic receiver functions are modeled using the first order structural observations of seismic discontinuities and EBSD data. They indicate 5% of anisotropy with slow symmetry axis in the upper crust, and demonstrate the importance of rock textural constraints in seismic velocity profile interpretation.
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Mayolle, Sylvain. « Croissance des zones d’endommagement de faille : étude structurale en milieu carbonaté et modélisations analogiques ». Thesis, Montpellier, 2021. http://www.theses.fr/2021MONTG019.
Texte intégralRésumé :
L’étude des failles affectant la croûte supérieure suscite un intérêt particulier pour la modélisation de leur impact sur l’écoulement des fluides et le comportement mécanique de la croûte terrestre. Les zones d’endommagements de failles sont d’importantes structures aux multiples implications pour les problématiques de gestions des ressources et de risque/aléa sismiques. Cette thèse a pour objectif de déterminer la distribution de l’endommagement autour des failles, comprendre sa croissance et étudier son impact sur la loi d’échelle Déplacement – Epaisseur d’endommagement (D-T). Pour répondre à cette problématique, deux approches complémentaires sont développées : des études tectoniques d’exemples naturels et des modélisations analogiques de failles normales. Ce manuscrit présente de nouvelles cartographies de l’endommagement, une première loi D-T pour les failles dans des roches carbonatées, ainsi que les premières expériences de modélisation analogique dédiées à l’étude de l’endommagement. Les résultats montrent que la distribution de l’endommagement autour des failles est hétérogène et asymétrique, principalement influencée par les nombreuses interactions de failles lors de leur croissance (segmentation, failles conjuguées). Une loi D-T spécifique à l’endommagement de type wall damage est établie, qui montre une corrélation normale entre D et T pour les failles de rejet inférieur à 100 m et confirme l’existence d’un seuil d’épaisseur d’endommagement au-delà de 100 m de rejet. Pour expliquer cette loi nous proposons un modèle de croissance de zone d’endommagement contrôlée par les processus d’interaction et de coalescence de la segmentation précoce. Les expériences de modélisations analogiques ont permis de décrire deux nouveaux types d’endommagement (graben damage et dip-change link damage), et d’identifier une transition de mode de déformation, depuis un cisaillement dilatant segmenté vers un cisaillement compactant localisé dans les zones de failles. Elles démontrent également que l’initiation de la segmentation, la sélection de l’activité des segments, leurs interactions et leurs coalescences sont des processus essentiels contrôlant le développement des zones d’endommagement et la loi D-T. Nous proposons que l’épaisseur de l’unité fragile contenant les failles est un paramètre principal du contrôle de l’évolution de la segmentation, de la localisation de la déformation et donc du seuil d’épaisseur d’endommagement observéThe study of faults in the upper crust generates interest in modeling their impact on fluid flow and the mechanical behavior of the earth's crust. Fault damage zones are important structures with multiple implications for resource management and earthquake studies. This thesis aims to characterize the distribution and growth of damage around faults and to study its impact on the Displacement - Damage thickness (D-T) scaling law. Two complementary approaches of field measurements and analog modeling of normal faults are developed to answer this question. This manuscript presents new results of fault damage mapping, D-T scaling in carbonate rocks, and the first analog modeling experiments of fault damage zones. The results show a heterogeneous and asymmetric distribution of damage around faults, mainly influenced by fault interactions during their growth (segmentation, conjugate faults). A D-T law specific to wall damage is established and shows a normal correlation between D and T for less than 100 m of fault displacement, and also confirms the existence of a damage thickness threshold after 100 m of displacement. To explain this law, we propose a damage zone growth model controlled by the interaction and coalescence of fault segments. Analog modeling experiments allowed the description of two new types of damage (graben damage and dip-change link damage), and show a failure mode transition during fault growth, from a segmented dilatational-shear mode to a localized compactional-shear mode. They also demonstrate that initiation of segmentation, segment activity selection, interaction and coalescence processes control the development of fault damage zones and the D-T law. We propose that the thickness of the faulted brittle layer is a main controlling parameter of segmentation, strain localization, and the fault damage thickness threshold observed
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Touma, Rita. « Approche matricielle de l’imagerie sismique passive par ondes de volume ». Thesis, Université Grenoble Alpes, 2022. http://www.theses.fr/2022GRALU011.
Texte intégralRésumé :
La structure des zones de faille a une directe implication sur l'évaluation des risques sismiques. Les techniques d'imagerie par réflexion, en particulier la migration, sont couramment utilisées pour imager le sous-sol. Un modèle de vitesse précis est souvent nécessaire pour localiser correctement les réflecteurs en profondeur. L'imagerie des zones de faille est un défi en raison de la distribution complexe de la vitesse des ondes de volume en leur sein. La plupart des techniques de réflexion imagent les zones de faille indirectement à partir de la discontinuité des couches géologiques. Les hétérogénéités à petite échelle, telles que les fissures et les fractures, sont généralement négligées. Dans cette thèse, nous proposons une approche d'imagerie matricielle pour l'exploration géophysique qui compense les variations de vitesse dans la croûte pour imager les hétérogénéités de cette dernière avec une résolution de l'ordre de la longueur d'onde autour des zones de faille.L'imagerie matricielle est inspirée de précédents travaux en imagerie ultrasonore et optique. D'une part, les corrélations du bruit ambiant sont utilisées pour construire la matrice de réflexion. La composante des ondes de volume dans cette matrice contient toute l'information disponible sur le milieu. D’autre part, l'approche présentée ne nécessite pas un modèle de vitesse détaillé du sous-sol.Dans une première application, nous utilisons des enregistrements de bruit ambiant dans la bande de fréquence [10 20] Hz provenant d'un réseau dense de géophones afin d'imager la faille de San Jacinto, Californie, à petite échelle. Les corrélations ZZ sont calculées et organisées en matrice 2D. En appliquant des lois de retard temporels sur les réponses impulsionnelles entre géophones, la matrice de réponse est projetée en profondeur, en se basant sur un modèle de vitesse homogène. Une matrice de réflexion focalisée est obtenue et contient les réponses impulsionnelles entre un ensemble de sources et récepteurs virtuels à chaque profondeur. A partir de cette matrice, l'image du milieu est construite et ses aberrations peuvent être quantifiées. La différence entre le modèle de vitesse considéré et la réalité entraînent des distorsions de phase, qui dégradent la résolution de l'image. Un processus de correction matricielle des aberrations permet de compenser ces distorsions en introduisant la matrice distorsion. Une image 3D des 4 premiers km de la croûte terrestre est obtenue avec une résolution huit fois plus fine que celle attendue en milieu homogène. Des différences de réflectivité sont observées entre le Nord-Ouest et le Sud-Est de la faille avec une zone de dommages intense et localisée dans le Sud-Est.Dans un deuxième cas d'étude, nous imageons la structure à grande échelle de la faille Nord Anatolienne en utilisant les corrélations horizontales [0.1 0.5] Hz calculées entre 73 paires de stations. Un modèle de vitesse multi-couches est considéré. Une correction locale des distorsions de phase est effectuée. La structure profonde des principaux blocs géologiques est révélée. Des différences dans la profondeur du Moho sont mises en lumière, avec un saut sous la branche nord. Une forte réflectivité est observée dans la région située le long de la branche Nord de la faille, coïncidant avec la limite des blocs lithosphériques. La diffusion dans le nord s'étend jusqu'à 60 km de profondeur, suggérant une zone de cisaillement qui pénètre dans le manteau supérieur sous la branche Nord.Dans la dernière partie de cette thèse, nous proposons une approche qui ouvre la voie à une tomographie passive 3D de la vitesse des ondes de volume. Enfin, toutes les applications présentées confirment l'efficacité de la matrice de réflexion pour révéler la distribution des hétérogénéités dans la croûte terrestre. Elle peut être appliquée sur n'importe quelle bande de fréquence, pourvu que l'échantillonnage spatial du réseau de géophones satisfasse au critère de NyquistRevealing the structure of fault zones provides insights required to assess seismic hazards. Reflection imaging methods, in particular migration, are commonly used to image the subsurface. An accurate velocity model is often needed to properly locate the reflectors in depth.Imaging fault zones is challenging due to the complex distribution of velocity. Also, most reflection techniques image fault zones indirectly from the discontinuity of geological layers. Wave diffraction by small-scale heterogeneities, such as cracks and fractures is generally neglected.In this thesis, we propose a matrix imaging approach for geophysical exploration that handles the velocity variation in the crust and allows to resolve heterogeneities of the order of the wavelength throughout the fault zone.The reflection matrix approach is inspired from previous studies in ultrasound and optical imaging of complex media. First, ambient noise cross-correlations are used to retrieve the reflection matrix associated with a dense array of geophones. The body wave components of this matrix contains all the information available on the medium. Second, the presented approach does not require a detailed velocity model of the subsurface. A set of matrix operation is applied to compensate for the mismatch between the actual wave velocity model and its approximate model.In a first application, we use ambient noise records in the frequency band [10 20] Hz from a dense array in order image the San Jacinto Fault, California, at small scale with an horizontal resolution of 80 m. ZZ cross-correlations are computed and arranged as 2D matrix. By applying time delays, the response matrix is projected to depth, using a homogeneous velocity model. A focused reflection matrix is obtained, that contains the impulse response between virtual sources and receivers at depth. From this matrix, the image of the medium is built and the resolution of the image can be quantified.Variations between the considered model and the reality result in phase distortions, i.e aberrations, that have detrimental effects on the image of the medium.We develop an aberration correction process that allows to compensate for these distortions by introducing a novel operator, the distortion matrix. 3D images of the first 4 km of the crust are retrieved. These images reveal the backscattered intensity generated by the heterogeneities in the medium. The location and reflectivity of scatterers are retrieved with a resolution 8 times better than the one in free space. Differences in the scattering between the Northwest and the Southeast of the fault were reported with an intense localized damage zone in the Southeast.In a second application, we image the large scale structure of North Anatolian Fault using [0.1 0.5] Hz horizontal cross-correlations computed between 73 pairs of stations. A multi-layered velocity model is considered. A local correction of the phase distortions is performed. The scattering structure of the crust and the upper mantle is revealed. Differences in the Moho depth are reported, with a step below the northern branch. Strong scattering is observed in the region lying along the northern strand of the fault, coinciding with the limit of the lithospheric blocks. The scattering in the North extends to 60 km depth, suggesting a shear zone that penetrates in the upper mantle beneath the northern strand. The scattering also reveals the deep structure of the main geological blocks.In the last part of this thesis, we propose an approach that paves the route towards a 3D passive tomography of the body wave velocity. Finally, all the presented applications confirm the efficiency of the reflection matrix approach in revealing the structure of the subsurface. It provides new insights into the scattering distribution in the Earth. It can be applied to any scale, scattering regime, and frequency bandwith, if the spatial sampling of the geophones' array satisfies the Nyquist criterion
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Koudashev, Oleg. « Large-Scale Structure and Geochronology of Porphyry and Epithermal Deposits Along the Northern Collisional Margin of the Australian Continental Lithosphere ». Phd thesis, Canberra, ACT : The Australian National University, 2016. http://hdl.handle.net/1885/144451.
Texte intégralRésumé :
In this thesis I combine 40Ar/39Ar geochronology and tectonics to investigate porphyry and epithermal deposits along the northern collisional margin of the Australian continental lithosphere using case studies on the islands of New Guinea and Sulawesi. The tectonic evolution of these islands reflects the effects of progressive northward movement after rifting off from Gondwana, with this movement involving interaction with multiple subduction zones and several accretion events. The island of New Guinea contains a number of world-class porphyry deposits forming the New Guinea copper-gold belt, including the world’s largest gold producer Grasberg. In comparision, the island of Sulawesi hosts multiple small and medium sized deposits but no major porphyries like New Guinea. The work reported here established the age of the hydrothermal system at the Yandera porphyry, located in the northern highlands of Papua New Guinea. The 3 Ma age obtained is younger than lithologies observed in drill core, or at the surface, suggesting that mineralisation in Yandera is genetically unrelated to the Yandera Porphyry suite of intrusives, making Yandera a detached/wallrock porphyry. Argon geochronology using step heating diffusion experiments was shown capable of identifying the age of hydrothermal overprinting, and providing an age for mineralisation U-Pb geochronology from an earlier study showed the porphyry suite to be 6.3-7.1 Ma. The age of ductile fabrics, interpreted to be related to an extensional shear zone, and metamorphism in the Bundi Fault Zone, north of the Yandera deposit, was established to be 8-13 Ma, which is coeval with the emplacement of the Bismarck Intrusive Complex and smaller satellite intrusives. These ages were much older than the mineralisation at Yandera. Thus the surface geology, except for younger fauts, was largely irrelevant to the formation of the deposit, except in respect to ground preparation. Geochronology of the Tombulilato, Tapadaa and Gunnung Pani deposits on the North Arm of Sulawesi also produced very young ages ranging from 5.5-1.8 Ma. Similar to Yandera,the Tapadaa porphyry deposit was also found to be hosted in an igneous intrusion that was older than the age of mineralisation, placing Tapadaa in a similar time period to the nearby epithermal deposits in Tombulilato. This thesis also reports the analysis of earthquake hypocenters and seismic tomography datasets, used to interpret the geometry and structure of subducted lithosphere beneath the areas of interest. The Yandera deposit and deposits in the North Arm of Sulawesi were found to be located above portions of subducted lithosphere adjacent to slab tears. Deposits were also found to be associated with structures and processes that should allow the fast ascent of magmas through the crust such as major strike-slip faults and uplift. Formation of the deposits of Tombulilato and Tapadaa was interpreted to occur as a result of north-directed subduction and rollback of the Molucca Sea Slab. Formation of the Yandera deposit was interpreted to occur due to tearing of subducted lithosphere as the result of oblique collision with the Finisterre terrane. The formation of these deposits was proposed to coincide with initiation of movement on nearby major strike-slip faults. (U-Th)/He geochronology showed that the Yandera deposit formed during a period of rapid denudation/exhumation of the New Guinea Highlands. Analysis of published ages conducted in this thesis for deposits in the Southwest Pacific indicates that the temporal distribution of these deposits is not random, suggesting region-scale controls on the formation of such deposits. This implies large scale tectonic and/or mantle processes play a part in the formation of such deposits. Possible geodynamic scenarios are discussed in the final chapter.
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Whitmarsh, Richard Sawyer. « Structural framework of the Fries fault zone south of Riner, Virginia ». Thesis, This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-09122009-040538/.
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Lange, Dietrich. « The South Chilean subduction zone between 41° and 43.5°S : seismicity, structure and state of stress ». Phd thesis, Universität Potsdam, 2008. http://opus.kobv.de/ubp/volltexte/2008/1894/.
Texte intégralRésumé :
Die stärksten Erdbeben treten an Subduktionszonen auf, so z.B. das stärkste instrumentell jemals gemessene Erdbeben vom 22. Mai 1960 mit einer Magnitude von 9,5 Mw in Süd Chile. In dieser Arbeit werden lokal gewonnene seismologische Daten aus dem zentralen Bereich des 1960er-Bebens vorgestellt. Das seismologische Netzwerk umfasste den chilenischen Forearc zwischen Tiefseegraben und den vulkanischen Bogen zwischen 41,5°-43,5°S und überdeckte sowohl die Insel Chiloé als auch die Nord-Süd-streichende Liquiñe-Ofqui Störungszone (LOFZ). Zwischen November 2004 und Oktober 2005 konnten 364 lokale Ereignisse registriert werden. Die gewonnen Aufzeichnungen erlauben Aussagen sowohl über das aktuelle Spannungsfeld im Forearc als auch über das lokale Geschwindigkeitsmodell und die Geometrie der subduzierten Benioff-Zone.
Mit einer Auswahl von P- und S-Laufzeiten von gut lokalisierbaren Erdbeben wurden ein Minimum 1-D Geschwindigkeitsmodell, Stationsresiduen und die Hypozentralparameter invertiert. Dieses Geschwindigkeitsmodell diente als Startmodell für die 2-D Tomographie. Das 2-D vp-Modell zeigt eine Zone erhöhter Geschwindigkeiten unterhalb des Längstals und des östlichen Bereiches der Insel Chiloé, die als Mantelaufwölbung interpretiert werden kann. Die Benioff-Zone wird als eine mit ca. 30° ostwärts einfallende Struktur abgebildet. Die seismische Hauptaktivität findet parallel zur Küste der Insel Chiloé in Tiefen zwischen 12 und 30 km statt; es handelt sich um Beben, die wahrscheinlich auf der Plattengrenzfläche stattfinden. In Tiefen über 70 km lässt die Seismizität bereits stark nach, die tiefsten Beben wurden in 120 km Tiefe registriert. Die Abwesenheit tieferer Seismizität wird auf das junge Alter (und eine damit verbundene hohe Temperatur) der ozeanischen Platte zurückgeführt.
Neben der Seismizität in der Benioff-Zone treten flache, krustale Beben in verschiedenen Häufungen entlang des magmatischen Bogens auf. Diese Bereiche erhöhter Seismizität sind räumlich mit der LOFZ und den Vulkanen Chaitén, Michinmahuida und Corcovado verknüpft. Beben bis zu einer Magnitude von 3,8 Mw zeigen die gegenwärtige Aktivität der LOFZ. Herdflächen entlang der LOFZ wurden aus Momententensor-Inversion anhand von Amplitudenspektren von Raumwellen gewonnen. Ergebnisse einer Spannungsfeldinversion zeigen ein Blattverschiebungsregime für den magmatischen Bogen und ein Überschiebungsregime für Beben in der Benioff-Zone auf. Die hier gemachten seismologischen Beobachtungen, zusammen mit teleseismischen Erdbeben und geologischen Befunden, unterstützen die Modellvorstellung eines sich nordwärts bewegenden kontinentalen Forearc-Blocks für Süd Chile.While the northern and central part of the South American subduction zone has been intensively studied, the southern part has attracted less attention, which may be due to its difficult accessibility and lower seismic activity. However, the southern part exhibits strong seismic and tsunamogenic potential with the prominent example of the Mw=9.5 May 22, 1960 Valdivia earthquake. In this study data from an amphibious seismic array (Project TIPTEQ) is presented. The network reached from the trench to the active magmatic arc incorporating the Island of Chiloé and the north-south trending Liquiñe-Ofqui fault zone (LOFZ). 364 local events were observed in an 11-month period from November 2004 until October 2005. The observed seismicity allows to constrain for the first time the current state of stress of the subducting plate and magmatic arc, as well as the local seismic velocity structure. The downgoing Benioff zone is readily identifiable as an eastward dipping plane with an inclination of ~30°. Main seismic activity occurred predominantly in a belt parallel to the coast of Chiloé Island in a depth range of 12-30 km, which is presumably related to the plate interface. The down-dip termination of abundant intermediate depth seismicity at approximately 70 km depth seems to be related to the young age (and high temperature) of the oceanic plate. A high-quality subset of events was inverted for a 2-D velocity model. The vp model resolves the sedimentary basins and the downgoing slab. Increased velocities below the longitudinal valley and the eastern part of Chiloé Island suggest the existence of a mantle bulge. Apart from the events in the Benioff Zone, shallow crustal events were observed mainly in different clusters along the magmatic arc. These crustal clusters of seismicity are related to the LOFZ, as well as to the volcanoes Chaitén, Michinmahuida and Corcovado. Seismic activity up to a magnitude of 3.8 Mw reveals the recent activity of the fault zone. Focal mechanisms for the events along the LOFZ were calculated using a moment tensor inversion of amplitude spectra for body waves which mostly yield strike-slip mechanisms indicating a SW-NE striking of sigma_1 for the LOFZ. Focal mechanism stress inversion indicates a strike-slip regime along the arc and a thrust regime in the Benioff zone. The observed deformation - which is also revealed by teleseismic observations - suggests a confirmation for the proposed northward movement of a forearc sliver acting as a detached continental micro-plate.
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Brown, James E. « Ion Microprobe δ18O-contraints on Fluid Mobility and Thermal Structure During Early Slip on a Low-angle Normal Fault, Chemehuevi Mountains, SE California ». Ohio University / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1448361194.
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Vitard, Clément. « Investigation sismique du domaine avant-arc Égéen du segment Sud-Ouest de la zone de subduction Hellénique ». Thesis, Université Côte d'Azur (ComUE), 2016. http://www.theses.fr/2016AZUR4116/document.
Texte intégralRésumé :
La zone de subduction Hellénique, en Méditerranée orientale, est caractérisée par le taux de sismicité le plus important d’Europe. Des séismes de forte magnitude (Mw 7,5-8) ont eu lieu le long du segment Sud-Ouest de la zone de subduction Hellénique, au large du Péloponnèse, au cours du 19ème et 20ème siècle. Ce segment de 400 km de long a également été le lieu de nucléation du plus important séisme d’Europe, en 365 ap J.C, avec une magnitude supérieure à 8, ayant entraîné un tsunami dévastateur. Deux principaux modèles scientifiques s’opposent sur la question du couplage sismique de l’interface de subduction, allant d’un couplage sismique total au niveau de l’interface, à l’hypothèse opposée d’un couplage quasi inexistant. Cependant, ces modèles opposés considèrent des géométries approximatives et parfois extrêmes, fautes de contraintes disponibles sur la structure et la géométrie de l’interplaque sous l’avant-arc dans cette zone. La localisation de la faille responsable du séisme de 365 ap J.C est également débattue, en l’absence de données géophysiques permettant d’identifier les interfaces potentiellement responsables de cet événement dévastateur. La faille de méga-chevauchement et le domaine avant-arc du segment Sud-Ouest de l’arc Hellénique ont été l’objet d’étude de la campagne océanographique Ulysse en Novembre 2012 afin de déterminer la géométrie des structures et unités majeures dans cette portion de la zone de subduction, mais également d’apporter un éclairage sur la tectonique récente qui affecte cette zoneThe Hellenic subduction zone, in the eastern part of the Mediterranean sea, is characterized by the highest rate of current seismicity in Europe. In the southwestern segment, several earthquakes of large magnitude (Mw 7,5-8) occured a the turn of the 19th to 20th century. This segment of 400 km long, has also been the nucleation site of the largest historical earthquake in Europe, named the 365 AD earthquake, with a magnitude of Mw 8. This event generates a devastating tsunami, which spread along the Adriactic Sea and in the Nile Delta region. Two main models differ about the interplate seismic coupling question in this region, from a total seismic coupling at the interplate, at the opposite assumption of a very weak seismic coupling. However, these opposing models consider an approximate geometry, mostly because of the lack of information available on the geometry and the localization of the interplate in this region of the forearc domain. The localization of the fault responsible of the 365 AD event is also debated, because, there is no available data who provides imagery of the interfaces potentially responsible of this devastating earthquake. The megathrust fault and the forearc domain of the southwestern segment of the Hellenic subduction zone has been the target of the Ulysse marine survey in November 2012. The aim of this survey was to provide information of the structural geometry of the main units in this part of the subduction zone, and to bring information on the recent tectonic activity in this region
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Heaverlo, Nicholas D. « Stress and strain rate estimates associated with penetrative deformation of the Harkless quartzite aureole rocks, Papoose Flat Pluton, California/Using structure contour maps to analyze subsurface 3D fault geometry along segments of the Moine Thrust ». Thesis, Virginia Tech, 2014. http://hdl.handle.net/10919/48425.
Texte intégralRésumé :
Dynamically recrystallized quartz microstructures preserved in contact aureoles allow for stress and strain rate estimates associated with penetrative deformation of rocks surrounding pluton margins. Microstructural analysis of the Harkless quartzites surrounding the western margin of Papoose Flat pluton indicates that recrystallization occurred by grain boundary migration with mean recrystallized grain size ranging from 86-225 µm. The application of three calibrated piezometers results in differential stress estimates between ~11 and ~29 MPa. Published wet-quartzite dislocation creep flow laws combined with deformation temperature, water fugacity, and differential stress estimates infer strain rates that range from 1.2 x 10⁻¹⁴ s⁻¹ to 2.3 x 10⁻¹² s⁻¹.
In order to analyze 3D subsurface fault geometry along map-pattern curves (salients and recesses), a structure contour map of the Moine thrust, extending from the North Coast southwards to the Dundonnel area, was constructed from 1:50,000 scale British Geological Survey (BGS) maps by correlating between elevation control points constrained by the intersection of the fault trace with topographic contours. The structure contour map indicates significant lateral variation in fault geometry along the Moine thrust, with recesses associated with antiformal corrugations in the subsurface and salients characterized by planar geometries or broad synformal corrugations. Additionally, structure contour maps constructed on the Glencoul thrust, as depicted by original BGS maps confirms that the thrust segments to the NE and SW of Loch Glencoul are part of the same structure, rather than different structures separated by a lateral ramp as shown on more recent BGS maps.Master of Science
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Kelly, Christina. « Understanding seismic properties of fault zones ». Thesis, University of Liverpool, 2014. http://livrepository.liverpool.ac.uk/17861/.
Texte intégralRésumé :
Fault zone properties at depth are often inferred from seismic properties such as seismic velocities and attenuation. An understanding of how fault zone properties and processes influence seismic measurements is required for successful interpretations to be made. As fault zones are heavily fractured and often fluid-rich areas, a knowledge of the influences of cracking and fluid content on seismic measurements is needed. This will allow better interpretation of fault zone properties and how they may change at the time of an earthquake. Research presented in this thesis is concentrated on two regions of strike-slip faulting: the Parkfield area of the San Andreas fault and the exhumed Carboneras fault zone region of SE Spain. Well-preserved exhumed faults allow observation of fault structure at seismogenic depths. The structure of the exhumed Carboneras fault has previously been suggested as an analogue for the Parkfield area at depth. Laboratory measurements can help us to determine what processes occur at seismogenic depths in active faults. They can also aid in interpretation of seismic studies. In this thesis laboratory and seismic studies are brought together in order to gain a greater understanding of fault zone seismic properties at depth and how to interpret them. In order to characterise the properties of the Carboneras fault, laboratory experiments of velocities through fault gouge and fault zone rocks are performed. The influences of fracture damage and local geological fabric on velocities are investigated. Gouge velocities are measured to be less than those of the mica schist rock through which the fault cuts. Velocity changes due to variations in crack damage in cyclic loading experiments are less than 5% of the original rock velocity. Strong velocity anisotropy is observed in the mica schist, with velocities of the order of 30% less when measured perpendicular to the strong foliation present in the rock. The consequences in terms of seismically imaging the fault zone are discussed. The effects of this strong velocity anisotropy need to be considered for specific source-receiver geometries and the local geological fabric in the locations of seismic experiments. Surface wave tomography and ambient noise analysis of the Carboneras fault zone region shows that faults are imaged as low velocity features at depth. Results suggest that velocities are reduced by approximately 10% at depths close to 3 km. The strong anisotropy observed in laboratory experiments of mica schist may also have implications for seismic imaging of this region as this rock crops out widely. This is discussed in terms of a potentially strong crustal component to shear-wave splitting observations in the region. In the second part of the thesis, temporal changes in seismic attenuation at the time of the 2004 M6.0 Parkfield earthquake are investigated. Seismic attenuation can give indications of fracture damage and healing. Spectral ratios between earthquakes within repeating clusters are calculated. A sharp increase in attenuation is observed immediately after the earthquake, which then decays over the next 2 years. The postseismic decay is fit by a logarithmic function. The timescale of the decay is found to be similar to that in GPS data and ambient seismic noise velocities following the 2004 M6.0 Parkfield earthquake. The amplitude of the attenuation change corresponds to a decrease of approximately 10% in QP at the time of the earthquake. The greatest changes are recorded to the northeast of the fault trace, consistent with preferential damage in the extensional quadrant behind a north-westerly propagating rupture tip. Our analysis suggests that significant changes in seismic attenuation and hence fracture dilatancy during co-seismic rupture are limited to depths of less than about 5 km.
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Bedrosian, Paul Andrew. « Electromagnetic imaging of active fault zones / ». Thesis, Connect to this title online ; UW restricted, 2002. http://hdl.handle.net/1773/9791.
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Traforti, Anna. « Reactivated fault zones : kinematic complexity and fault rock spectral characterization ». Doctoral thesis, Università degli studi di Padova, 2018. http://hdl.handle.net/11577/3421819.
Texte intégralRésumé :
In the present work three main factors contributing to the overall complexity of reactivated fault zones have been investigated: i) the problematic reconstruction of polyphase brittle tectonic evolution accommodated by fault zones dissecting lithologically heterogeneous rock domains; ii) the estimate of the mechanical anisotropy associated with pre-existing planar discontinuities (i.e., metamorphic foliations and inherited faults) steering their brittle reactivation process; iii) the spectral characterization of fault zone rocks in complex fault architectures aimed at inferring the distribution of fault zone domains by means of remote sensing techniques.
In order to achieve the goal of improving current understanding of these factors defining reactivated fault zone complexity, different methodologies have been applied: i) a paleostress inversion analysis that carefully considers each analyzed fault zones and the different mechanical behavior of the lithological domains they deform; ii) a bootstrapping statistical approach aimed at evaluating the homogeneity between the resulting stress tensors and identifying possible local stress perturbations; iii) a normalised slip tendency analysis that, integrated with paleostress reconstructions and detailed meso- and micro-structural observations, allows constraining the mechanical properties of pre-existing planar discontinuities; iv) a spectral features analysis of fault zone rock reflectance spectra, aimed at highlighting the correlation between variations in fault rock spectral signatures and grain size reduction related to fault comminution processes.
The main results of this work highlighted that: i) polyphase brittle tectonics within lithologically heterogeneous rock domains can be efficiently unrevealed by applying a paleostress inversion combined with bootstrapping statistical analysis of the resulting reduced stress tensors; ii) normalised slip tendency analysis can be considered a reliable method to investigate and constrain the weakness of pre-existing anisotropies at a regional scale (104-103 m); iii) the grain size reduction resulting from fault-related comminution processes on mineralogically homogenous bedrocks (carbonates in this case) influences the spectral signatures of fault rock samples, which absorption feature parameters vary systematically with the grain size in the VNIR and SWIR wavelength ranges; iv) consequently, remote sensing analysis, based on fault rock reflectance spectrum variabilities due to comminution processes, has a good potential in the identification of the spatial distribution and extent of fault core and damage zone domains (i.e., characterized by different grain sizes) on mineralogically homogenous bedrocks (carbonates in this case).Nel presente lavoro sono stati investigati tre fattori che contribuiscono alla definizione della complessità delle zone di faglia riattivate: i) la ricostruzione dell’evoluzione tettonica polifasica accomodata da zone di faglia che interessano litologie eterogenee; ii) la stima del grado di anisotropia meccanica associata alla presenza di discontinuità planari pre-esistenti (i.e., foliazioni metamorfiche e faglie), il quale influenza i meccanismi di riattivazione lungo tali piani; iii) la caratterizzazione spettrale delle rocce di faglia, finalizzata all’ identificazione della distribuzione delle zone di danno e di core tramite tecniche di remote sensing, con particolare riguardo a zone di faglie mature aventi un’architettura complessa. Al fine di dare un nuovo contributo alla comprensione dei fattori che definiscono le complessità insite nelle zone di faglia riattivate, sono state applicate diverse metodologie che comprendono: i) l’inversione del campo di paleostress, applicata considerando il comportamento meccanico dei domini litologici interessati da ogni differente zona di faglia; ii) l’approccio statistico di tipo ‘bootstrapping’ applicato al fine di valutare l’omogeneità tra i tensori di stress ricavati e di identificare possibili perturbazioni locali del campo di paleostress; iii) la ‘normalised slip tendensy analysis’ che, integrata alla ricostruzione del campo di paleostress e ad una caratterizzazione di tipo micro- e meso-strutturale, permette di stimare quantitativamente le proprietà meccaniche di discontinuità planari pre-esistenti; iv) l’analisi delle bande di assorbimento osservate negli spettri di riflettenza di diverse rocce di faglia, al fine di evidenziare il rapporto esistente tra le variazioni osservate nei parametri spettrali e i processi di comminuzione dovuti all’evolversi della zona di faglia stessa. I principali risultati di questo lavoro evidenziano come: i) tettoniche polifasiche che si sviluppano in domini rocciosi altamente eterogenei possono essere efficacemente ricostruite applicando in maniera integrata l’inversione del campo di paleostress e l’analisi statistica di tipo ‘bootstrapping’; ii) la ‘normalised slip tendency analysis’ permette di investigare la debolezza di anisotropie pre-esistenti a scala regionale (104-103 m); iii) la riduzione granulometrica connessa ai processi di comminuzione dovuti all’evolversi di una zona di faglia in rocce incassanti omogenee dal punto di vista mineralogico (carbonati in questo caso) influenza la firma spettrale delle rocce di faglia, le cui bande di assorbimento hanno caratteristiche che variano sistematicamente con la diminuzione della granulometria; iv) di conseguenza, l’analisi in remoto, basata sugli effetti della comminuzione sulle firme spettrali delle rocce di faglia, dimostra un buon potenziale nell’identificazione della distribuzione spaziale delle zone di danno e di core di una faglia in rocce incassanti omogenee dal punto di vista mineralogico.
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Ouazzani-Touhami, Mohamed. « Structures et recristallisations associees dans des zones de cisaillement : nappes de mascate (oman) et nappes de frederico s.l. (rif interne, maroc) ». Université Louis Pasteur (Strasbourg) (1971-2008), 1986. http://www.theses.fr/1986STR13198.
Texte intégralRésumé :
L'etude de la deformation et des recristallisations associees dans deux ensembles de nappes synmetamorphiques (mascate, oman; rif, maroc) a abouti a montrer que, dans les deux exemples, il apparait que les isogrades du metamorphisme sont perturbes par des chevauchements tardi- a post-metamorphiques, qui jouent un role important dans les dernieres phases de l'evolution thermique des piles tectoniques considerees. Les nappes de mascate (oman) representent un element tres interne, en fenetre, sous les nappes oceaniques chainees sur la plateforme arabe. En ce qui concerne les nappes de federico (rif, maroc), on montre que le plissement synmetamorphique est un pli isoclinal couche, et que l'empilement des unites semble s'etre fait du sud vers le nord, en sens contraire de celui du chevauchement tardif (miocene)
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Dodson, Elizabeth Lauren. « STRUCTURAL GEOLOGY OF THE TRANSYLVANIA FAULT ZONE IN BEDFORD COUNTY, PENNSYLVANIA ». UKnowledge, 2009. http://uknowledge.uky.edu/gradschool_theses/621.
Texte intégralRésumé :
Transverse zones cross strike of thrust-belt structures as large-scale alignments of cross-strike structures. The Transylvania fault zone is a set of discontinuous right-lateral transverse faults striking at about 270º across Appalachian thrust-belt structures along 40º N latitude in Pennsylvania. Near Everett, Pennsylvania, the Breezewood fault terminates with the Ashcom thrust fault. The Everett Gap fault terminates westward with the Hartley thrust fault. Farther west, the Bedford fault extends westward to terminate against the Wills Mountain thrust fault. The rocks, deformed during the Alleghanian orogeny, are semi-independently deformed on opposite sides of the transverse fault, indicating fault movement during folding and thrusting.
Palinspastic restorations of cross sections on either side of the fault zone are used to compare transverse fault displacement. The difference in shortening corresponds to the amount of displacement on either side of the transverse fault. The palinspastic restoration indicates a difference in the amount of shortening that will balance farther to the west in the Appalachian Plateau province.