Статті в журналах: "Fault rheology"

1

Lavallée, Yan, Takehiro Hirose, Jackie E. Kendrick, Kai-Uwe Hess, and Donald B. Dingwell. "Fault rheology beyond frictional melting." Proceedings of the National Academy of Sciences 112, no. 30 (June 29, 2015): 9276–80. http://dx.doi.org/10.1073/pnas.1413608112.

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During earthquakes, comminution and frictional heating both contribute to the dissipation of stored energy. With sufficient dissipative heating, melting processes can ensue, yielding the production of frictional melts or “pseudotachylytes.” It is commonly assumed that the Newtonian viscosities of such melts control subsequent fault slip resistance. Rock melts, however, are viscoelastic bodies, and, at high strain rates, they exhibit evidence of a glass transition. Here, we present the results of high-velocity friction experiments on a well-characterized melt that demonstrate how slip in melt-bearing faults can be governed by brittle fragmentation phenomena encountered at the glass transition. Slip analysis using models that incorporate viscoelastic responses indicates that even in the presence of melt, slip persists in the solid state until sufficient heat is generated to reduce the viscosity and allow remobilization in the liquid state. Where a rock is present next to the melt, we note that wear of the crystalline wall rock by liquid fragmentation and agglutination also contributes to the brittle component of these experimentally generated pseudotachylytes. We conclude that in the case of pseudotachylyte generation during an earthquake, slip even beyond the onset of frictional melting is not controlled merely by viscosity but rather by an interplay of viscoelastic forces around the glass transition, which involves a response in the brittle/solid regime of these rock melts. We warn of the inadequacy of simple Newtonian viscous analyses and call for the application of more realistic rheological interpretation of pseudotachylyte-bearing fault systems in the evaluation and prediction of their slip dynamics.

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Verberne, Berend A., Oliver Plümper, and Christopher J. Spiers. "Nanocrystalline Principal Slip Zones and Their Role in Controlling Crustal Fault Rheology." Minerals 9, no. 6 (May 28, 2019): 328. http://dx.doi.org/10.3390/min9060328.

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Principal slip zones (PSZs) are narrow (<10 cm) bands of localized shear deformation that occur in the cores of upper-crustal fault zones where they accommodate the bulk of fault displacement. Natural and experimentally-formed PSZs consistently show the presence of nanocrystallites in the <100 nm size range. Despite the presumed importance of such nanocrystalline (NC) fault rock in controlling fault mechanical behavior, their prevalence and potential role in controlling natural earthquake cycles remains insufficiently investigated. In this contribution, we summarize the physical properties of NC materials that may have a profound effect on fault rheology, and we review the structural characteristics of NC PSZs observed in natural faults and in experiments. Numerous literature reports show that such zones form in a wide range of faulted rock types, under a wide range of conditions pertaining to seismic and a-seismic upper-crustal fault slip, and frequently show an internal crystallographic preferred orientation (CPO) and partial amorphization, as well as forming glossy or “mirror-like” slip surfaces. Given the widespread occurrence of NC PSZs in upper-crustal faults, we suggest that they are of general significance. Specifically, the generally high rates of (diffusion) creep in NC fault rock may play a key role in controlling the depth limits to the seismogenic zone.

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OOHASHI, Kiyokazu, Toru TAKESHITA, and Ken-ichi HIRAUCHI. "Evolution of Fault Zones and Its Rheology." Journal of Geography (Chigaku Zasshi) 129, no. 4 (August 25, 2020): 473–89. http://dx.doi.org/10.5026/jgeography.129.473.

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4

van der Elst, Nicholas J., Andrew A. Delorey, David R. Shelly, and Paul A. Johnson. "Fortnightly modulation of San Andreas tremor and low-frequency earthquakes." Proceedings of the National Academy of Sciences 113, no. 31 (July 18, 2016): 8601–5. http://dx.doi.org/10.1073/pnas.1524316113.

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Earth tides modulate tremor and low-frequency earthquakes (LFEs) on faults in the vicinity of the brittle−ductile (seismic−aseismic) transition. The response to the tidal stress carries otherwise inaccessible information about fault strength and rheology. Here, we analyze the LFE response to the fortnightly tide, which modulates the amplitude of the daily tidal stress over a 14-d cycle. LFE rate is highest during the waxing fortnightly tide, with LFEs most strongly promoted when the daily stress exceeds the previous peak stress by the widest margin. This pattern implies a threshold failure process, with slip initiated when stress exceeds the local fault strength. Variations in sensitivity to the fortnightly modulation may reflect the degree of stress concentration on LFE-producing brittle asperities embedded within an otherwise aseismic fault.

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5

Liao, Chun-Fu, Strong Wen, Chau-Huei Chen, and Ying-Nien Chen. "Exploring the Rheology of a Seismogenic Zone by Applying Seismic Variation." Applied Sciences 11, no. 19 (September 23, 2021): 8847. http://dx.doi.org/10.3390/app11198847.

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Although the study of spatiotemporal variation of a subsurface velocity structure is a challenging task, it can provide a description of the fault geometry as well as important information on the rheological changes caused by fault rupture. Our main objective is to investigate whether rheological changes of faults can be associated with the seismogenic process before a strong earthquake. For this purpose, a 3D tomographic technique is applied to obtain P- and S-wave velocity structures in central Taiwan using travel time data. The results show that temporal variations in the Vs structure in the source area demonstrate significant spatiotemporal variation before and after the Chi-Chi earthquake. We infer that, before the mainshock, Vs began to decrease (and Vp/Vs increased) at the hanging wall of the Chelungpu fault, which may be induced by the increasing density of microcracks and fluid. However, in the vicinity of the Chi-Chi earthquake’s source area, Vs increased (and Vp/Vs decreased), which may be attributed to the closing of cracks or migration of fluid. The different physical characteristics at the junctional zone may easily generate strong earthquakes. Therefore, seismic velocity changes are found to be associated with a subsurface evolution around the source area in Taiwan. Our findings suggest that monitoring the Vp and Vs (or Vp/Vs) structures in high seismic potential zones is an important ongoing task, which may minimize the damage caused by future large earthquakes.

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Ault, A. K., J. L. Jensen, R. G. McDermott, F. A. Shen, and B. R. Van Devener. "Nanoscale evidence for temperature-induced transient rheology and postseismic fault healing." Geology 47, no. 12 (October 15, 2019): 1203–7. http://dx.doi.org/10.1130/g46317.1.

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Abstract Friction-generated heat and the subsequent thermal evolution control fault material properties and thus strength during the earthquake cycle. We document evidence for transient, nanoscale fault rheology on a high-gloss, light-reflective hematite fault mirror (FM). The FM cuts specularite with minor quartz from the Pleistocene El Laco Fe-ore deposit, northern Chile. Scanning and transmission electron microscopy data reveal that the FM volume comprises a <50-μm-thick zone of polygonal hematite nanocrystals with spherical silica inclusions, rhombohedral twins, no shape or crystallographic preferred orientation, decreasing grain size away from the FM surface, and FM surface magnetite nanoparticles and Fe2+ suboxides. Sub–5-nm-thick silica films encase hematite grains and connect to amorphous interstitial silica. Observations imply that coseismic shear heating (temperature >1000 °C) generated transiently amorphous, intermixed but immiscible, and rheologically weak Fe-oxide and silica. Hematite regrowth in a fault-perpendicular thermal gradient, sintering, twinning, and a topographic network of nanometer-scale ridges from crystals interlocking across the FM surface collectively restrengthened fault material. Results reveal how temperature-induced weakening preconditions fault healing. Nanoscale transformations may promote subsequent strain delocalization and development of off-fault damage.

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Bachura, M., T. Fischer, J. Doubravová, and J. Horálek. "From earthquake swarm to a main shock–aftershocks: the 2018 activity in West Bohemia/Vogtland." Geophysical Journal International 224, no. 3 (November 4, 2020): 1835–48. http://dx.doi.org/10.1093/gji/ggaa523.

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SUMMARY In earthquake swarms, seismic energy is released gradually by many earthquakes without a dominant event, which offers detailed insight into the processes on activated faults. The swarm of May 2018 that occurred in West Bohemia/Vogtland region included more than 4000 earthquakes with ML =〈0.5, 3.8&x3009 x232A;and its character showed significant changes during the two weeks duration: what started as a pure earthquake swarm ended as a typical main shock–aftershock sequence. Based on precise double-difference relocations, four fault segments differing in strikes and dips were identified with similar dimensions. First, two segments of typical earthquake swarm character took place, and at the end a fault segment hosting a main shock–aftershock sequence was activated. The differences were observable in the earthquakes spatio-temporal evolutions (systematic versus disordered migration of the hypocentres), b-values (>1.3 for the swarm, <1 for the main shock–aftershocks), or the smoothness of seismic moment spatial distribution along the fault plane. Our findings can be interpreted by local variations of fault rheology, differential stress and/or smoothness of the faults surface, possibly related to the crustal fluids circulating along the fault plane and their interplay with the seismic cycle.

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Dotseva, Zornitsa, Dian Vangelov, and Ianko Gerdjikov. "The Botevgrad basin main characteristics and evolution." Geologica Balcanica 47, no. 2 (November 2018): 47–58. http://dx.doi.org/10.52321/geolbalc.47.2.47.

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The Botevgrad basin is one of the numerous Late Pliocene–Quaternary basins developed over the Balkanide orogen. The basin is developed in the West Balkan tectonic zone and on the northern slopes of the Stara Planina Mountain along the Plakalnitsa fault zone, the front of the orogen. The basin was interpreted as half-graben formed on the SW block of the Dragoybalkan fault, considered as the Plakalnitsa fault zone’s extensionally reactivated roots. Our data suggest that the basin formation is more complicated and all basin boards are fault predestined. The boards are morphologically well prominent and their geometry is a result of the reactivated older faults’ segmentation, combined with the different rheology of the basement lithologies, mainly Palaeozoic low-grade metamorphites and intruded into them syn- to post-metamorphic granitoids. The distribution of the numerous depocentres, the orientation of drainage systems, watershed shape and depositional system migration indicate polyphasic basin evolution. The basin shape and other data, such as criteria for sense of shearing, and intrabasinal push-up blocks’ rotation, suggest that the Botevgrad basin should be interpreted as pull-apart basin.

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9

Héja, Gábor Herkules, Zsolt Kercsmár, Szilvia Kövér, Tamás Budai, Mohamed Yazid Noui, and László Fodor. "The Role of Rheology and Fault Geometry on Fault Reactivation: A Case-Study from the Zsámbék-Mány Basin, Central Hungary." Geosciences 12, no. 12 (November 24, 2022): 433. http://dx.doi.org/10.3390/geosciences12120433.

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In this study, we investigated the structural evolution of the Vértessomló (VT) Thrust and the Környe-Zsámbék (KZ) Fault, which are located in the Transdanubian Range in the center of the Miocene Pannonian back-arc basin. Our study is based on surface and well data. The Transdanubian Range was located on the Adriatic passive margin during the Late Triassic, where a thick succession of platform carbonates was deposited. Intercalations of intraplatform basin deposits occur in the eastern part of the study area. South-directed thrusting and the formation of the VT Thrust took place during the Cretaceous, related to the Austroalpine orogeny. Asymmetric half-grabens were formed during the Eocene in the hanging wall of the segmented dextral normal KZ Fault. The geometry and kinematics of the KZ Fault were influenced by the pre-existing VT Thrust located in the Mesozoic basement of the Paleogene sub-basins. These Eocene half-grabens suffered mild inversion due to the dextral reverse reactivation of the VT Thrust and the KZ Fault during the Oligocene–Early Miocene. The geometry of Miocene normal faults indicates that the VT-KZ Fault system was an active transfer fault during the Miocene extension of the Pannonian Basin, as well. We found a positive correlation between the rheology of the Triassic basement and the mode of Paleogene fault reactivation. Our results show that reactivation of the pre-existing thrust took place along that segment, where the Triassic basement is made up of homogeneous platform carbonates. In contrast, a diffuse fault zone developed, where the Triassic basement is represented by the weak layers of intraplatform basins.

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Preuss, Simon, Jean Paul Ampuero, Taras Gerya, and Ylona van Dinther. "Characteristics of earthquake ruptures and dynamic off-fault deformation on propagating faults." Solid Earth 11, no. 4 (July 22, 2020): 1333–60. http://dx.doi.org/10.5194/se-11-1333-2020.

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Abstract. Natural fault networks are geometrically complex systems that evolve through time. The evolution of faults and their off-fault damage patterns are influenced by both dynamic earthquake ruptures and aseismic deformation in the interseismic period. To better understand each of their contributions to faulting we simulate both earthquake rupture dynamics and long-term deformation in a visco-elasto-plastic crust subjected to rate- and state-dependent friction. The continuum mechanics-based numerical model presented here includes three new features. First, a 2.5-D approximation is created to incorporate the effects of a viscoelastic lower crustal substrate below a finite depth. Second, we introduce a dynamically adaptive (slip-velocity-dependent) measure of fault width to ensure grid size convergence of fault angles for evolving faults. Third, fault localization is facilitated by plastic strain weakening of bulk rate and state friction parameters as inspired by laboratory experiments. This allows us to simulate sequences of episodic fault growth due to earthquakes and aseismic creep for the first time. Localized fault growth is simulated for four bulk rheologies ranging from persistent velocity weakening to velocity strengthening. Interestingly, in each of these bulk rheologies, faults predominantly localize and grow due to aseismic deformation. Yet, cyclic fault growth at more realistic growth rates is obtained for a bulk rheology that transitions from velocity-strengthening friction to velocity-weakening friction. Fault growth occurs under Riedel and conjugate angles and transitions towards wing cracks. Off-fault deformation, both distributed and localized, is typically formed during dynamic earthquake ruptures. Simulated off-fault deformation structures range from fan-shaped distributed deformation to localized splay faults. We observe that the fault-normal width of the outer damage zone saturates with increasing fault length due to the finite depth of the seismogenic zone. We also observe that dynamically and statically evolving stress fields from neighboring fault strands affect primary and secondary fault growth and thus that normal stress variations affect earthquake sequences. Finally, we find that the amount of off-fault deformation distinctly depends on the degree of optimality of a fault with respect to the prevailing but dynamically changing stress field. Typically, we simulate off-fault deformation on faults parallel to the loading direction. This produces a 6.5-fold higher off-fault energy dissipation than on an optimally oriented fault, which in turn has a 1.5-fold larger stress drop. The misalignment of the fault with respect to the static stress field thus facilitates off-fault deformation. These results imply that fault geometries bend, individual fault strands interact, and optimal orientations and off-fault deformation vary through space and time. With our work we establish the basis for simulations and analyses of complex evolving fault networks subject to both long-term and short-term dynamics.

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Wells, Rachel K., Julie Newman, and Steven Wojtal. "Microstructures and rheology of a calcite-shale thrust fault." Journal of Structural Geology 65 (August 2014): 69–81. http://dx.doi.org/10.1016/j.jsg.2014.04.002.

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Kirkpatrick, James D., and Emily E. Brodsky. "Slickenline orientations as a record of fault rock rheology." Earth and Planetary Science Letters 408 (December 2014): 24–34. http://dx.doi.org/10.1016/j.epsl.2014.09.040.

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McDivitt, Jordan A., Steffen G. Hagemann, Nicolas Thébaud, Laure A. J. Martin, and Kai Rankenburg. "Deformation, Magmatism, and Sulfide Mineralization in the Archean Golden Mile Fault Zone, Kalgoorlie Gold Camp, Western Australia." Economic Geology 116, no. 6 (September 1, 2021): 1285–308. http://dx.doi.org/10.5382/econgeo.4836.

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Abstract The Golden Mile fault zone is a key controlling structure to the estimated 75 Moz gold endowment of the Kalgoorlie gold camp in the Yilgarn craton of Western Australia. The earliest structures in the fault are F1 folds that developed during D1 recumbent-fold and thrust deformation (<2685 ± 4 Ma). These F1 folds are overprinted by a pervasive NW- to NNW-striking S2 cleavage related to sinistral shearing beginning with 2680 ± 3 Ma D2a sinistral strike-slip and culminating with ca. 2660 Ma D2c sinistral-reverse movement. The majority of deformation in the fault zone correlates to ca. 2675 Ma D2b deformation, which is characterized by sinistral-normal kinematic indicators. Late, ca. 2650–2640 Ma D3 dextral-reverse kinematic indicators overprint the earlier D2 structures. Pyrrhotite-chalcopyrite-pyrite-sphalerite-galena assemblages were emplaced throughout the D2 event within NE-trending D2a tensile fractures, NW- to NNW-striking D2b normal faults and associated breccias, and NW- to NNW-striking D2c low-angle veins, with the latter D2b and D2c structures correlating to the Fimiston and Oroya mineralization types, respectively. All D2a-, D2b-, and D2c-related sulfides in the Golden Mile fault zone show similarly restricted δ34S (~1.0–4.5‰) and elevated Δ33S (~2.0–3.0‰) values that reflect strong local sulfur contribution from shales of the Lower Black Flag Group and host-rock buffering of hydrothermal fluids related to the Fimiston and Oroya mineralization events. This host-rock buffering decreased fluid fO2, favoring the development of pyrrhotite-pyrite stable sulfide assemblages and causing respective decreases and increases in fluid Au-Te and Pb-Bi-Sb concentrations. At the camp scale, the Golden Mile fault zone exerted a primary control on the distribution of porphyry dikes and gold deposits; however, magma and hydrothermal fluid circulation was favored in adjacent, higher-order structural sites due to the fault zone’s incompetent rheology and tendency for ductile deformation and diffuse fluid flow. Other Archean examples such as Au deposits of the Larder Lake-Cadillac deformation zone in the Superior craton illustrate that this type of diffuse fluid flow in large-scale crustal fault zones can result in disseminated economic mineralization. However, this study highlights that host-rock effects on fluid chemistry in large-scale crustal fault zones exercises a strong control on a fluid’s propensity to form ore. The results of this study emphasize that both the rheology and chemistry of rocks within and adjacent to large-scale deformation zones act as important controls on the formation of gold ore in Archean terranes.

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Sone, Hiroki, and Takahiko Uchide. "Spatiotemporal evolution of a fault shear stress patch due to viscoelastic interseismic fault zone rheology." Tectonophysics 684 (August 2016): 63–75. http://dx.doi.org/10.1016/j.tecto.2016.04.017.

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Wu, Patrick. "Will earthquake activity in eastern Canada increase in the next few thousand years?" Canadian Journal of Earth Sciences 35, no. 5 (May 1, 1998): 562–68. http://dx.doi.org/10.1139/e97-125.

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Knowledge of whether earthquake activity will increase in the next few thousand years is important for the planning of nuclear waste repositories. Assuming that fault instability portends earthquake activity, the rate of change in fault instability for the next few thousand years in eastern Canada is computed for two viscosity models. It is shown that a uniform-viscosity (1 x 1021 Pa ·s) mantle predicts decreasing fault instability. However, a high-viscosity (1 x 1023 Pa ·s) lower mantle predicts a significant increase in fault instability, with an overall rate of -0.06 MPa/ka. Due to the lack of consensus on lower mantle viscosity, the case for increasing earthquake activity is definitely a possibility, so more study on mantle rheology, ice deglaciation history, and intraplate earthquakes in the planning of nuclear waste repositories is needed.

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Sullivan, Walter A., and Emma J. O’Hara. "A natural example of brittle-to-viscous strain localization under constant-stress conditions: a case study of the Kellyland fault zone, Maine, USA." Geological Magazine 159, no. 3 (November 15, 2021): 421–40. http://dx.doi.org/10.1017/s0016756821001035.

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AbstractThis article integrates field, powder X-ray diffraction and microstructural data to constrain deformation mechanisms in and the rheology of granite-derived fault rocks exposed along the SE side of the crustal-scale, strike-slip Kellyland fault zone. Deformation in this area of the Kellyland fault zone localized during cooling and is marked by (1) foliated granite, (2) a ∼50 m wide band of pulverized foliated granite, (3) a ∼2.8 m wide breccia zone hosting coeval shear zones, and (4) a >100 m wide ultramylonite zone. The earliest fabric in the foliated granite is defined by elongated quartz grains, and quartz dislocation creep was the rate-controlling deformation mechanism. Seismogenic deformation initiated when recorded flow stresses reached 96–104 MPa at temperatures of 400–450 °C and is marked by coeval pulverization and formation of breccia. Interseismic viscous creep at similar flow stresses is recorded by mutual cross-cutting relationships between breccia-hosted shear zones, brittle fractures and pseudotachylyte. Field and microstructural observations indicate that breccia-hosted shear zones are low-strain equivalents of the >100 m wide ultramylonite zone, and seismogenic deformation abated as the ultramylonite formed. The rheology of ultramylonites was governed by grain-size-sensitive creep at 112–124 MPa flow stresses. Hence, from the onset of seismogenesis, the Kellyland fault zone was likely a constant-stress system wherein the rate-controlling mechanism shifted from episodic seismogenic slip and interseismic viscous creep to steady state grain-size-sensitive creep in ultramylonites derived from brittle fault rocks. Flow stresses recorded by these rocks also imply that the whole zone was relatively weak if the brittle–viscous transition and uppermost viscous zone are the strongest part of the crust.

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Amoruso, A., L. Crescentini, M. Dragoni, and A. Piombo. "Fault slip controlled by gouge rheology: a model for slow earthquakes." Geophysical Journal International 159, no. 1 (October 2004): 347–52. http://dx.doi.org/10.1111/j.1365-246x.2004.02386.x.

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Copley, Alex, and Romain Jolivet. "Fault rheology in an aseismic fold-thrust belt (Shahdad, eastern Iran)." Journal of Geophysical Research: Solid Earth 121, no. 1 (January 2016): 412–31. http://dx.doi.org/10.1002/2015jb012431.

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Beeler, N. M., Amanda Thomas, Roland Bürgmann, and David Shelly. "Inferring fault rheology from low-frequency earthquakes on the San Andreas." Journal of Geophysical Research: Solid Earth 118, no. 11 (November 2013): 5976–90. http://dx.doi.org/10.1002/2013jb010118.

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Sieberer, Anna-Katharina, Ernst Willingshofer, Thomas Klotz, Hugo Ortner, and Hannah Pomella. "Inversion of extensional basins parallel and oblique to their boundaries: inferences from analogue models and field observations from the Dolomites Indenter, European eastern Southern Alps." Solid Earth 14, no. 7 (July 4, 2023): 647–81. http://dx.doi.org/10.5194/se-14-647-2023.

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Abstract. Polyphase deformation of continental crust is analysed through physical analogue models for settings wherein platform–basin geometries at passive continental margins are subject to subsequent shortening and orogenesis. In a first stage, segmentation of the brittle and brittle–ductile models into basins and platforms is achieved by extension. Basins are partly filled with brittle material to allow for a strength difference between basin and platform realms, simulating relatively weaker, incompetent deposits of grabens surrounded by competent pre-rift basement or carbonate platform rock, respectively. In a second stage of deformation, contraction parallel and oblique (10 to 20∘) to the basin axes has been applied, leading to the inversion of basins formed earlier. The experiments show that strength contrasts across platform–basin transitions control the localisation and overall style of compressional deformation, irrespective of the nature of the basal décollement (frictional versus viscous), the rheology of the basin fill, or changing platform–basin thickness ratios. Orientations of thrust faults change laterally across inherited platform–basin transitions throughout all experiments; higher obliquity of basin inversion leads to stronger alignment of thrust curvature with the orientation of pre-existing rift axes. At individual thrust faults, variations in the strike of thrust fronts are accompanied by changes in the shortening direction during incremental phases of deformation. Reactivation of normal faults occurs in oblique basin inversion settings only, favourably at platform–basin transitions where the normal faults face the shortening direction. The amount and style of fault reactivation depend on the material used. Our experiments are relevant for natural cases such as the Dolomites Indenter of the eastern Southern Alps, underlining the importance of inherited geologic features for the subsequent shortening geometries. Field structural data from the western segment of the Belluno thrust of the Valsugana fault system support predicted variations of thrust fault orientation and a lateral change in shortening direction (from SSW to SSE along-strike) along one single fault. Based on our modelling results, we suggest that this variability of thrust fault orientation and shortening directions, controlled by inherited structures, is consistent with strain partitioning during a single phase of deformation and does not necessarily reflect different deformation phases.

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Liu, Yunhua, Dezheng Zhao, and Xinjian Shan. "Asymmetric Interseismic Strain across the Western Altyn Tagh Fault from InSAR." Remote Sensing 14, no. 9 (April 28, 2022): 2112. http://dx.doi.org/10.3390/rs14092112.

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As the northern boundary of the Tibetan Plateau, the long Altyn Tagh fault (ATF) controls the regional tectonic environment, and the study of its long-term fault slip rate is key to understanding the tectonic evolution and deformation of the northern Tibetan Plateau. In this paper, we measure the fault slip rate of the western segment of the ATF using InSAR observations between 2015 to 2020. The Multi-Temporal Interferometric InSAR analysis is applied to obtain the two-dimensional fault-parallel and vertical displacement fields. The spatially dense InSAR observations clearly illustrate the asymmetrical pattern of displacement fields across the fault. Constrained by our InSAR observations, the fault slip rate and locking depth of the western segment of the ATF are inverted using four different models in a Bayesian framework. The two-layer viscoelastic model incorporating lateral heterogeneity of rheology in the lower crust indicates that the fault slip rate of the western ATF is estimated to be 9.8 ± 1.1 mm/yr (at 83.8°E across the ATF) and 8.6 ± 1.1 mm/yr (at 85.1°E), respectively, and the locking depth is 15.8 ± 4.3 km and 14.8 ± 4.9 km. Our new estimates generally agree with the previous estimates of fault slip rate constrained by GPS observations. We conclude that the contrast between the thickness of the elastic layer and the shear modulus of the Tibetan plateau and the Tarim basin jointly contribute to the asymmetric interseismic strain accumulation on the ATF.

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Wang, Kelin, Herb Dragert, and H. Jay Melosh. "Finite element study of uplift and strain across Vancouver Island." Canadian Journal of Earth Sciences 31, no. 10 (October 1, 1994): 1510–22. http://dx.doi.org/10.1139/e94-134.

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Geological evidence for sudden coastal subsidence along the west coast of southern Vancouver Island points to the occurrence of great prehistorical subduction earthquakes. Contemporary uplift and crustal shortening patterns in southern Vancouver Island appear to indicate that the subduction megathrust fault is currently locked. To understand better the dynamics of the observed surface deformation, we develop a finite element model of earthquake cycles for the northern Cascadia subduction zone across southern Vancouver Island, using a linear viscoelastic rheology. The model consists of the continental and oceanic lithospheres, the asthenospheric mantle with a viscosity of 5 × 1019 Pa∙s, and a low-viscosity (1018 Pa∙s) mantle wedge between the subducted oceanic plate and the overlying continental plate. The shallow geometry of the subducted Juan de Fuca plate is well defined by the results of various geophysical surveys, and the deep geometry is constrained by the results of seismic tomography. The model megathrust fault has a stick-slip zone near the surface, a viscoelastically weakly coupled zone (viscosity 7 × 1017 Pa∙s) at depth, and a narrow free-slip zone in between. Earthquakes are allowed to occur every 500 years. Varying the recurrence time does not greatly affect the surface deformation in the later part of the interseismic period. Experiments varying the width of the stick-slip zone lead to the conclusion that a width of about 70 km satisfies both the observed coseismic coastal subsidence and the contemporary surface deformation pattern. The results of a simple elastic dislocation model for thrust earthquakes that had been previously applied to the region are compared with the solutions of the viscoelastic model. Despite its simplicity, the elastic model approximates well the surface deformation of the viscoelastic model in the second half of the interseismic period, although it predicts a slightly narrower stick-slip zone of the fault. The present viscoelastic model is limited principally by the two-dimensional approach, the assumptions of purely stick-slip behaviour of the thrust fault, and the uncertainties in rock rheology.

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He, Jiankun, Shuangjiang Lu, and Xinguo Wang. "Mechanical relation between crustal rheology, effective fault friction, and strike-slip partitioning among the Xiaojiang fault system, southeastern Tibet." Journal of Asian Earth Sciences 34, no. 3 (March 2009): 363–75. http://dx.doi.org/10.1016/j.jseaes.2008.06.003.

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24

Guerrero, Jesús. "Dissolution collapse of a growing diapir from radial, concentric, and salt-withdrawal faults overprinting in the Salinas de Oro salt diapir, northern Spain." Quaternary Research 87, no. 2 (March 2017): 331–46. http://dx.doi.org/10.1017/qua.2016.17.

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AbstractA geomorphic investigation of the Salinas de Oro salt diapir in the Pyrenees reveals that the ring fracture pattern related to the karstic collapse of the diapir crest may vary significantly depending on the rates of dissolution and salt flow, and the rheology of the overburden. The salt diapir has well-developed concentric faults related to salt dissolution subsidence throughout the Quaternary. Roof strata accommodate subsidence by a combination of downward sagging and brittle collapse leading to the development of a ring monocline that is broken by 5 to 20 m throw conjugated normal faults and a 40 m throw, 9.5-km-long and 200-m-wide keystone graben. The salt diapir top has >100-m-long sinkholes that coalesce to form hollows >70 m deep. Up to 3-km-long radial grabens with a 70 to 90 m vertical throw overprint concentric-ring faulting and displace Quaternary deposits demonstrating active salt flow and diapir rise. Radial faults are linked with salt-withdrawal faults of the Andia Fault Zone (AFZ). Salt flow from the AFZ into the Salinas de Oro salt diapir causes brittle gravitational extension of limestone strata leading to a sequence of grabens and Quaternary faults >10 km long and several hundred meters deep.

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25

Blanpied, M. L., C. J. Marone, D. A. Lockner, J. D. Byerlee, and D. P. King. "Quantitative measure of the variation in fault rheology due to fluid-rock interactions." Journal of Geophysical Research: Solid Earth 103, B5 (May 10, 1998): 9691–712. http://dx.doi.org/10.1029/98jb00162.

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26

Belardinelli, Maria Elina, and Maurizio Bonafede. "Rheology heterogeneities on fault surfaces inferred from the time history of afterslip events." Geophysical Journal International 116, no. 2 (February 1994): 349–65. http://dx.doi.org/10.1111/j.1365-246x.1994.tb01802.x.

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27

Lyakhovsky, Vladimir, and Yehuda Ben-Zion. "Evolving geometrical and material properties of fault zones in a damage rheology model." Geochemistry, Geophysics, Geosystems 10, no. 11 (November 2009): n/a. http://dx.doi.org/10.1029/2009gc002543.

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28

Bull, Jonathan M., and Roger A. Scrutton. "Fault reactivation in the central Indian Ocean and the rheology of oceanic lithosphere." Nature 344, no. 6269 (April 1990): 855–58. http://dx.doi.org/10.1038/344855a0.

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29

Tang, Chi-Chia, Han Xu, Lupei Zhu, Rong Huang, and Yinhe Luo. "Detecting repeating aftershocks in the Three Gorges Reservoir region, Central China." Geophysical Journal International 221, no. 2 (January 29, 2020): 1402–11. http://dx.doi.org/10.1093/gji/ggaa049.

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SUMMARY Slippage on a deep fault, which cannot be directly measured, can be inferred from repeating earthquakes. Here, we use a matched filter technique (MFT) to detect missing earthquakes near the Xiannvshan fault in the Three Gorges Reservoir region of Central China. We detected 13 repeating aftershock sequences (RASs) containing 107 events after a Ms 4.4 local earthquake that occurred on 26 March 2014. The RASs occurred in the vicinity of the Ms 4.4 main shock hypocentre and were concentrated within a depth range of 4–7 km. The short-term slip rates estimated from these RASs varied from ∼0.001 to 0.31 mm d–1. The slip rates of the RASs followed an approximately logarithmic decay with RAS duration, suggesting that the deep Xiannvshan fault behaviour tended to follow the logarithmic velocity-strengthening friction law. Relatively high-stress RAS events seemed to influence the occurrence of other RAS events whereas we found no evidence that high-stress nearby events, including a Ms 4.6 local earthquake that occurred on 29 March 2014, triggered the RAS events. We suggest that the fault stress change caused by the Ms 4.4 main shock played a role in triggering the RAS events. Our results demonstrate that the MFT can effectively help identify repeating aftershocks, which could help decipher fault zone rheology.

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30

Rybacki, E., C. Janssen, R. Wirth, K. Chen, H. R. Wenk, D. Stromeyer, and G. Dresen. "Low-temperature deformation in calcite veins of SAFOD core samples (San Andreas Fault) — Microstructural analysis and implications for fault rheology." Tectonophysics 509, no. 1-2 (August 2011): 107–19. http://dx.doi.org/10.1016/j.tecto.2011.05.014.

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31

Stephen, R. Polis, T. Angelich Michael, R. Beeman Charles, B. Maze William, J. Reynolds David, M. Steinhauff David, Tudoran Andrei, and V. Wood Mark. "Preferential deposition and preservation of structurally-controlled synrift reservoirs: Northeast Red Sea and Gulf of Suez." GeoArabia 10, no. 1 (January 1, 2005): 97–124. http://dx.doi.org/10.2113/geoarabia100197.

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ABSTRACT An integrated GIS-based play evaluation, which incorporates restorations of the North Red Sea and Gulf of Suez, has helped to identify potentially prospective areas in the Northeast Red Sea associated with point-sourced synrift sandstone reservoirs. The three largest synrift Gulf of Suez fields (Belayim Land, Belayim Marine, and Morgan) are located along major fault-transfer zones that optimized the conditions for the deposition and preservation of thick point-sourced sands adjacent to extensive hydrocarbon source kitchens. Belayim Land and Morgan fields contain stacked submarine fan, delta, and alluvial fan systems that developed during the deposition of the Miocene Rudeis, Kareem, and Belayim-South Gharib formations, respectively. This continuous, point-sourced sedimentation is indicative of stable drainage and by inference, a stable eastern border fault system. We attribute this stable border fault system to a stress heterogeneity related to the pre-existing Najd Shear Zone, and polarity reversals in upper-plate transport direction. Tectonic restorations indicate that the North Red Sea, like the Gulf of Suez, should have reservoir facies deposited in similar structural positions, but preservation is a significant risk due to additional crustal extension. Although crestal block erosion remains a great concern for reservoir preservation, seismic mapping indicates that block size along the coastal region and inboard areas are similar to the Gulf of Suez. This suggests that most of the strain may have been accommodated along the warmer axial portion of the rift where weaker crustal rheology exists. Landsat mapping of the Northeast Red Sea border fault system has found a high degree of variability in structural styles. The southern Yanbu-Jeddah and Umm Luj-Al Wajh sub-basins are bound by listric, down-to the west-southwest border faults, separated by suture-controlled accommodation zones. To the north, the Midyan-Ifal sub-basin is located along the Miocene flexural margin, and is structurally more complex. Northwesterly-trending (Najd Shear Zone) planar faults are overprinted by a strong northeasterly (Aqaba) trend, such that transpressional and transtensional features exist. Although structurally complex, the offshore northern flexural margin has been determined to have the best potential for localized, second-generation, thick, synrift sediments similar to that of the Gulf of Suez.

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32

Samsu, Anindita, Weronika Gorczyk, Timothy Chris Schmid, Peter Graham Betts, Alexander Ramsay Cruden, Eleanor Morton, and Fatemeh Amirpoorsaeed. "Selective inversion of rift basins in lithospheric-scale analogue experiments." Solid Earth 14, no. 8 (August 29, 2023): 909–36. http://dx.doi.org/10.5194/se-14-909-2023.

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Abstract. Basin inversion is commonly attributed to the reverse reactivation of basin-bounding normal faults. This association implies that basin uplift and inversion-related structures are mainly controlled by the frictional behaviour of pre-existing faults and associated damage zones. In this study, we use lithospheric-scale analogue experiments of orthogonal extension followed by shortening to explore how the flow behaviour of ductile layers underneath rift basins promote or suppress basin inversion. Our experiments show that the rheology of the ductile lower crust and lithospheric mantle, modulated by the imposed bulk strain rate, determine (1) basin distribution in a wide rift setting and (2) strain accommodation by fault reactivation and basin uplift during subsequent shortening. When the ductile layers deform uniformly during extension (i.e. stretching) and shortening (i.e. thickening), all of the basins are inverted. When deformation in the ductile layers is localised during extension (i.e. necking) and shortening (i.e. folding), only some basins – which are evenly spaced apart – are inverted. We interpret the latter as selective basin inversion, which may be related to the superposition of crustal-scale and lithospheric-scale boudinage during the previous basin-forming extensional phase and/or folding of the ductile layers during shortening.

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33

Ando, Ryosuke, Naoto Takeda, and Teruo Yamashita. "Propagation dynamics of seismic and aseismic slip governed by fault heterogeneity and Newtonian rheology." Journal of Geophysical Research: Solid Earth 117, B11 (November 2012): n/a. http://dx.doi.org/10.1029/2012jb009532.

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34

Liu, Sibiao, Zhikui Guo, Lars H. Rüpke, Jason P. Morgan, Ingo Grevemeyer, Yu Ren, and Chuanzhi Li. "Sensitivity of gravity anomalies to mantle rheology at mid-ocean ridge – transform fault systems." Earth and Planetary Science Letters 622 (November 2023): 118420. http://dx.doi.org/10.1016/j.epsl.2023.118420.

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35

Motuzas, Charlotte A., and Robert Shcherbakov. "Viscoelastic Slider Blocks as a Model for a Seismogenic Fault." Entropy 25, no. 10 (October 6, 2023): 1419. http://dx.doi.org/10.3390/e25101419.

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In this work, a model is proposed to examine the role of viscoelasticity in the generation of simulated earthquake-like events. This model serves to investigate how nonlinear processes in the Earth’s crust affect the triggering and decay patterns of earthquake sequences. These synthetic earthquake events are numerically simulated using a slider-block model containing viscoelastic standard linear solid (SLS) elements to reproduce the dynamics of an earthquake fault. The simulated system exhibits elements of self-organized criticality, and results in the generation of avalanches that behave similarly to naturally occurring seismic events. The model behavior is analyzed using the Epidemic-Type Aftershock Sequence (ETAS) model, which suitably represents the observed triggering and decay patterns; however, parameter estimates deviate from those resulting from natural aftershock sequences. Simulated aftershock sequences from this model are characterized by slightly larger p-values, indicating a faster-than-normal decay of aftershock rates within the system. The ETAS fit, along with realistic simulated frequency-size distributions, supports the inclusion of viscoelastic rheology to model the seismogenic fault dynamics.

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36

Cao, Kai, Philippe Hervé Leloup, Guocan Wang, Wei Liu, Gweltaz Mahéo, Tianyi Shen, Yadong Xu, Philippe Sorrel, and Kexin Zhang. "Thrusting, exhumation, and basin fill on the western margin of the South China block during the India-Asia collision." GSA Bulletin 133, no. 1-2 (April 30, 2020): 74–90. http://dx.doi.org/10.1130/b35349.1.

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Abstract The pattern and timing of deformation in southeast Tibet resulting from the early stages of the India-Asia collision are crucial factors to understand the growth of the Tibetan Plateau, but they remain poorly constrained. Detailed field mapping, structural analysis, and geochronological and thermochronological data along a 120 km section of the Ludian-Zhonghejiang fold-and-thrust belt bounding the Jianchuan basin in western Yunnan, China, document the early Cenozoic tectonic evolution of the conjunction between the Lanping-Simao and South China blocks. The study area is cut by two major southwest-dipping brittle faults, named the Ludian-Zhonghejiang fault and the Tongdian fault from east to west. Numerous kinematic indicators and the juxtaposition of Triassic metasedimentary rocks on top of Paleocene strata indicate thrusting along the Ludian-Zhonghejiang fault. Similarly, structural analysis shows that the Tongdian fault is a reverse fault. Between these structures, fault-bounded Permian–Triassic and Paleocene rocks are strongly deformed by nearly vertical and upright southwest-vergent folds with axes that trend nearly parallel to the traces of the main faults. Zircon and apatite (U-Th)/He and apatite fission-track data from a Triassic pluton with zircon U-Pb ages of 237–225 Ma in the hanging wall of the Ludian-Zhonghejiang fault, assisted by inverse modeling, reveal two episodes of accelerated cooling during 125–110 Ma and 50–39 Ma. The Cretaceous cooling event was probably related to crustal thickening during the collision between the Lhasa and Qiangtang terranes. The accelerated exhumation during 50–39 Ma is interpreted to record the life span of the fold-and-thrust belt. This timing is corroborated by the intrusive relationship of Eocene magmas of ca. 36–35 Ma zircon U-Pb age into the fold-and-thrust belt. Early Cenozoic activity of the deformation system controlled deposition of alluvial-fan and braided-river sediments in the Jianchuan basin, as evidenced by eastward and northeastward paleoflows and terrestrial clasts derived from the hanging wall of the Ludian-Zhonghejiang thrust. Since 39 Ma, decreasing cooling rates likely reflect cessation of activity on the fold-and-thrust belt. Early Cenozoic compressive deformation on the western margin of the South China block together with geological records of contraction in central, northern, and eastern Tibet document Eocene upper-crustal shortening located in the Himalaya, Qiangtang terrane, and northern plateau margins together with contractional basin development in the intervening Lhasa, Songpan-Garze, and Kunlun terranes, coeval with or shortly after the onset of the India-Asia collision. This suggests that moderate crustal shortening affected a large part of Tibet in a spaced way, contrary to models of homogeneous crustal thickening soon after the collision, and prior to the main crustal thickening, propagating progressively from south to north. This complex deformation pattern illustrates the complexity of Asian crustal rheology, which contrasts with assumptions in existing geodynamic models.

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37

Reches, Ze'ev, Gerald Schubert, and Charles Anderson. "Modeling of periodic great earthquakes on the San Andreas Fault: Effects of nonlinear crustal rheology." Journal of Geophysical Research: Solid Earth 99, B11 (November 10, 1994): 21983–2000. http://dx.doi.org/10.1029/94jb00334.

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38

Qi, Chuang, Yan-Li Zhu, Fei Gao, Song-Cen Wang, Kai Yang, and Qing-Jie Jiao. "Safety analysis of lithium-ion battery by rheology-mutation theory coupling with fault tree method." Journal of Loss Prevention in the Process Industries 49 (September 2017): 603–11. http://dx.doi.org/10.1016/j.jlp.2017.06.006.

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39

Ruggia, Giacomo, Susan Ivy-Ochs, Jordan Aaron, Olivia Steinemann, Silvana Martin, Manuel Rigo, Sandro Rossato, Christof Vockenhuber, Giovanni Monegato, and Alfio Viganò. "Reconstructing the Gorte and Spiaz de Navesele Landslides, NE of Lake Garda, Trentino Dolomites (Italy)." Geosciences 11, no. 10 (September 25, 2021): 404. http://dx.doi.org/10.3390/geosciences11100404.

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We applied a multi-method approach to reconstruct the Gorte rock avalanche (85–95 Mm3) located at the northeastern end of Lake Garda. The combination of field mapping, characterization of bedrock discontinuities, Dan3D-Flex runout modeling and dating of boulders with cosmogenic 36Cl supports the conclusion that the deposits stem from a single rock avalanche at 6.1 ± 0.8 ka. The Gorte event may have triggered the Spiaz de Navesele–Salto della Capra landslide (3.2 Mm3), whose deposits cover the southern end of the Gorte deposits. First-order controls on detachment were the NNE–SSW- and WNW–ESE-oriented fractures in the limestone bedrock, related to the Giudicarie and Schio-Vicenza fault systems, respectively. Dan3D-Flex runout modeling sufficiently reproduced the Gorte rock avalanche, which involved detachment and sliding of a quasi-intact block, likely along marly interbeds, followed by rapid disintegration. The frictional rheology in the source area and the turbulent frictional rheology (Voellmy) in the remaining part best replicate the observed deposit extent and thickness. Heavy precipitation that occurred at that time may have contributed to failure at Gorte. Nonetheless, its timing overlaps with the nearby (<15 km) Dosso Gardene (6630–6290 cal BP) and Marocca Principale (5.3 ± 0.9 ka) landslides, making a seismic trigger plausible.

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40

Tsutsumi, Akito, and Toshihiko Shimamoto. "Dynamic evolution of deformation microstructures in rocks. Microstructures and rheology in fault rocks. Frictional properties of monzodiorite and gabbro during seismogenic fault motion." Journal of the Geological Society of Japan 102, no. 3 (1996): 240–48. http://dx.doi.org/10.5575/geosoc.102.240.

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41

Ishii, Eiichi. "Predictions of the highest potential transmissivity of fractures in fault zones from rock rheology: Preliminary results." Journal of Geophysical Research: Solid Earth 120, no. 4 (April 2015): 2220–41. http://dx.doi.org/10.1002/2014jb011756.

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42

Muto, J., J. D. P. Moore, S. Barbot, T. Iinuma, Y. Ohta, and H. Iwamori. "Coupled afterslip and transient mantle flow after the 2011 Tohoku earthquake." Science Advances 5, no. 9 (September 2019): eaaw1164. http://dx.doi.org/10.1126/sciadv.aaw1164.

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Modeling of postseismic deformation following great earthquakes has revealed the viscous structure of the mantle and the frictional properties of the fault interface. However, for giant megathrust events, viscoelastic flow and afterslip mechanically interplay with each other during the postseismic period. We explore the role of afterslip and viscoelastic relaxation and their interaction in the aftermath of the 2011 Mw (moment magnitude) 9.0 Tohoku earthquake based on a detailed model analysis of the postseismic deformation with laterally varying, experimentally constrained, rock rheology. Mechanical coupling between viscoelastic relaxation and afterslip notably modifies both the afterslip distribution and surface deformation. Thus, we highlight the importance of addressing mechanical coupling for long-term studies of postseismic relaxation, especially in the context of the geodynamics of the Japan trench across the seismic cycle.

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43

Laurich, Ben, Janos L. Urai, Christian Vollmer, and Christophe Nussbaum. "Deformation mechanisms and evolution of the microstructure of gouge in the Main Fault in Opalinus Clay in the Mont Terri rock laboratory (CH)." Solid Earth 9, no. 1 (January 9, 2018): 1–24. http://dx.doi.org/10.5194/se-9-1-2018.

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Abstract. We studied gouge from an upper-crustal, low-offset reverse fault in slightly overconsolidated claystone in the Mont Terri rock laboratory (Switzerland). The laboratory is designed to evaluate the suitability of the Opalinus Clay formation (OPA) to host a repository for radioactive waste. The gouge occurs in thin bands and lenses in the fault zone; it is darker in color and less fissile than the surrounding rock. It shows a matrix-based, P-foliated microfabric bordered and truncated by micrometer-thin shear zones consisting of aligned clay grains, as shown with broad-ion-beam scanning electron microscopy (BIB-SEM) and optical microscopy. Selected area electron diffraction based on transmission electron microscopy (TEM) shows evidence for randomly oriented nanometer-sized clay particles in the gouge matrix, surrounding larger elongated phyllosilicates with a strict P foliation. For the first time for the OPA, we report the occurrence of amorphous SiO2 grains within the gouge. Gouge has lower SEM-visible porosity and almost no calcite grains compared to the undeformed OPA. We present two hypotheses to explain the origin of gouge in the Main Fault: (i) authigenic generation consisting of fluid-mediated removal of calcite from the deforming OPA during shearing and (ii) clay smear consisting of mechanical smearing of calcite-poor (yet to be identified) source layers into the fault zone. Based on our data we prefer the first or a combination of both, but more work is needed to resolve this. Microstructures indicate a range of deformation mechanisms including solution–precipitation processes and a gouge that is weaker than the OPA because of the lower fraction of hard grains. For gouge, we infer a more rate-dependent frictional rheology than suggested from laboratory experiments on the undeformed OPA.

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44

Pauselli, Cristina, and Giorgio Ranalli. "Effects of lateral variations of crustal rheology on the occurrence of post-orogenic normal faults: The Alto Tiberina Fault (Northern Apennines, Central Italy)." Tectonophysics 721 (November 2017): 45–55. http://dx.doi.org/10.1016/j.tecto.2017.09.008.

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45

Le Pourhiet, L., B. Huet, and N. Traoré. "Links between long-term and short-term rheology of the lithosphere: Insights from strike-slip fault modelling." Tectonophysics 631 (September 2014): 146–59. http://dx.doi.org/10.1016/j.tecto.2014.06.034.

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46

Spray, John G. "Viscosity determinations of some frictionally generated silicate melts: Implications for fault zone rheology at high strain rates." Journal of Geophysical Research: Solid Earth 98, B5 (May 10, 1993): 8053–68. http://dx.doi.org/10.1029/93jb00020.

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47

Steffen, Rebekka, Patrick Wu, Holger Steffen, and David W. Eaton. "The effect of earth rheology and ice-sheet size on fault slip and magnitude of postglacial earthquakes." Earth and Planetary Science Letters 388 (February 2014): 71–80. http://dx.doi.org/10.1016/j.epsl.2013.11.058.

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48

Brink, U. S., N. C. Miller, B. D. Andrews, D. S. Brothers, and P. J. Haeussler. "Deformation of the Pacific/North America Plate Boundary at Queen Charlotte Fault: The Possible Role of Rheology." Journal of Geophysical Research: Solid Earth 123, no. 5 (May 2018): 4223–42. http://dx.doi.org/10.1002/2017jb014770.

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49

Clausen, Ole Rønø, John A. Korstgård, and Tommy Mogensen Egebjerg. "Quantitative strain analysis of strike-slip displacements across the Arne-Elin trend, the Danish Central Graben." Bulletin of the Geological Society of Denmark 43 (December 5, 1996): 99–113. http://dx.doi.org/10.37570/bgsd-1996-43-11.

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A method is presented for unravelling the displacement history across transpressionand transtension zones recognized on seismic sections as flower structures. The method has been applied to the Arne-Elin trend in the northern part of the Danish Central Graben. The results suggest sinistral movement with alternating transpression and transtension along strike during the Early Cretaceous, and dextral transpressive movement during the Late Cretaceous and Paleogene. However, there is considerable variation in displacement along strike of the zone during the individual periods. The variation in displacement along the strike of the Arne-Elin trend is accommodated by displacement along the fault systems in the adjoining areas. The displacement along fault systems in the adjoining areas was sinistral during the Early Cretaceous and dextral during the post-Early Cretaceous, similar to the movement along the Arne-Elin trend during the two periods. The analysis gives a detailed picture of the movements along the general structural trend and emphasizes the differences between the two periods. One of the most marked differences is that the fault system separating the Gertrud Graben, the Feda Graben and the Heno Plateau becomes locked during the Late Cretaceous/Paleogene while the Arne-Elin trend is strongly inverted. Observations show that the major inversion structures are often underlain by Zechstein salt. Contemporaneous normal faulting (local extension), however, took place without involvement of salt. The onset of inversion of previously generated structures therefore depended not only on changes in the regional stress system, but also seems to be controlled by the rheology of the rocks involved.

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50

Pinto, Victor Hugo Guimarães, Gianreto Manatschal, Anne Marie Karpoff, Emmanuel Masini, Rodolfo Araújo Victor, Adriano Roessler Viana, and Marc Ulrich. "Mass-Transfer and Fluid Flow along Extensional Detachment Faults in Hyperextended Rift Systems: The Examples of Tasna in the Alps, Mauléon in the Pyrenees, and Hobby High Offshore Iberia." Geosciences 13, no. 12 (December 8, 2023): 374. http://dx.doi.org/10.3390/geosciences13120374.

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Hyperextended rift systems are characterized by extreme crustal thinning and mantle exhumation associated with extensional detachment faults. These faults cut through thinned continental crust, reaching the underlying mantle and allowing for seawater to infiltrate and react with the crustal and mantle rocks. Hydrothermal fluid systems linked to detachment faults result in fluid–rock reactions occurring along the detachments, resulting in the breakdown and alteration of minerals, loss of elements and strain weakening in both mantle and crustal rocks. We present new geological observations and geochemical data from the modern Iberia and fossil Alpine Tethys Ocean Continent Transition and the West Pyrenean Mauléon hyperextended rift basin. We show evidence for a km-scale fluid flow along detachment faults and discuss the conditions under which fluid flow and mass transfer occurred. Convective fluid systems are of major importance for mass transfer between the mantle, crustal and marine reservoirs. We identified gains in Si, Mg, Fe, Mn, Ca, Ni, Cr and V along extensional detachment faults that we relate to channelized, hydrothermal crust- and mantle-reacted fluid systems migrating along detachments in the hyperextended continental crust. The observation that fault rocks of extensional detachment and syn-extensional sedimentary rocks are enriched in mantle-derived elements such as Cr, Ni and V enables us to define the pathways of fluids, as well as to estimate their age relative to detachment faulting and sedimentation. Because all three examples show a similar mass transport of elements along detachment systems at km-scale, we conclude that these examples are linked to convective fluid systems that may affect the thermal state of the lithosphere, as well as the rheology and chemistry of rocks in hyperextended systems, and may have implications for ore mineral exploration in hyperextended rift systems.

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