Статті в журналах з теми "Inverted fault zones"
Щоб переглянути інші типи публікацій з цієї теми, перейдіть за посиланням: Inverted fault zones.
Оформте джерело за APA, MLA, Chicago, Harvard та іншими стилями
Ознайомтеся з топ-50 статей у журналах для дослідження на тему "Inverted fault zones".
Біля кожної праці в переліку літератури доступна кнопка «Додати до бібліографії». Скористайтеся нею – і ми автоматично оформимо бібліографічне посилання на обрану працю в потрібному вам стилі цитування: APA, MLA, «Гарвард», «Чикаго», «Ванкувер» тощо.
Також ви можете завантажити повний текст наукової публікації у форматі «.pdf» та прочитати онлайн анотацію до роботи, якщо відповідні параметри наявні в метаданих.
Переглядайте статті в журналах для різних дисциплін та оформлюйте правильно вашу бібліографію.
1
Stewart, Simon A. "Detachment-controlled triangle zones in extension and inversion tectonics." Interpretation 2, no. 4 (November 1, 2014): SM29—SM38. http://dx.doi.org/10.1190/int-2014-0026.1.
Повний текст джерелаАнотація:
“Triangle zone” geometry is well established in thrust tectonics, where the leading edge of a frontal thrust branches backward onto a hinterland-directed roof thrust, and the triangle zone thus formed defines the thrust system’s leading edge. Similar geometries occur in extension and inversion settings, where a triangle zone can form between a deep-seated master fault and a roof fault or backthrust located in a hanging-wall detachment. In basement-controlled extension, triangle zone development can occur when the shear strength of the master fault plane in the zone above a hanging-wall detachment cutoff exceeds that of a new or reactivated antithetic fault detaching on the hanging-wall dip slope. This structural style is characterized by pronounced hanging-wall synclines linked to detached extensional faults higher up the hanging-wall dip slopes. The same principles apply during early phases of inversion tectonics. The part of the master fault that is above the hanging-wall detachment cutoff may constitute a buttress that causes displacement to backthrust along any available detachment into accommodation structures such as emergent ramps. This structural style is characterized by compressional structures within the graben while there is minor or even no sign of inversion on the graben margin faults. These geometries could be accounted for by other processes, for example, localized deep-seated fault-controlled structures within graben, or salt redistribution. However, fieldwork and analog models demonstrate the admissibility of triangle zone kinematics across a range of tectonic settings in the presence of detachment layers that are thin relative to the overall stratigraphy — typically tens to hundreds of meters in thickness. These models can guide seismic interpretation of unusual fold structures in extensional and inverted graben. Seismic interpretation examples were evaluated from the North Sea and Saudi Arabia.
2
Muhammad, Yanis, Abdullah Faisal, Assyifa Yenny, Zainal Muzakir, Marwan Abubakar, and Ismail Nazli. "CONTINUITY OF GREAT SUMATRAN FAULT IN THE MARINE AREA REVEALED BY 3D INVERSION OF GRAVITY DATA." Jurnal Teknologi 83, no. 1 (December 13, 2020): 145–55. http://dx.doi.org/10.11113/jurnalteknologi.v83.14824.
Повний текст джерелаАнотація:
The Great Sumatran Fault (GSF) is a 1900-km-long fault extending from Lampung, Indonesia, to India's Andaman Islands. The fault location is not only on the land but also in the marine area. Previous studies were only focused on the land area of Sumatra and Andaman Islands even though the marine fault has also impacted earthquakes and tsunamis such as in 2004. As an effort to disaster risk mitigation, this study used the gravity method to map and study the continuity of the GSF in the marine area from the Aceh Province, Indonesia, to the Andaman Islands, India. The gravity data were obtained from Topex with a resolution of 1.85 km/px. Based on the Bouguer data, the subduction zone in the western part of the Indian Ocean is observed with the anomaly of 500–700 mGal, while the residual structure of GSF, relative to the subduction zone, only comes to clarity through a horizontal derivative transformation with anomaly 130-250 mGal. To delineate the fault's geometry, the data were inverted by GRABLOX 1.6 using Singular Value Decomposition and Occam methods. The 3D modeling results also clearly show the contrast density between regional faults such as subduction zones on the Westside of the West Andaman Fault (WAF). The GSF faults can also be well demonstrated at 50 km depth. Based on these results, the gravity Topex is potentially used as a preliminary study of the GSF activity in the marine area.
3
Konstantinovskaya, Elena A., Lyal B. Harris, Jimmy Poulin, and Gennady M. Ivanov. "Transfer zones and fault reactivation in inverted rift basins: Insights from physical modelling." Tectonophysics 441, no. 1-4 (August 2007): 1–26. http://dx.doi.org/10.1016/j.tecto.2007.06.002.
Повний текст джерела
4
Vassileva, Magdalena S., Mahdi Motagh, Thomas R. Walter, Hans-Ulrich Wetzel, and Sergey L. Senyukov. "The 29 March 2017 Yuzhno-Ozernovskoe Kamchatka Earthquake: Fault Activity in An Extension of the East Kamchatka Fault Zone as Constrained by InSAR Observations." Bulletin of the Seismological Society of America 110, no. 3 (May 12, 2020): 1101–14. http://dx.doi.org/10.1785/0120190174.
Повний текст джерелаАнотація:
ABSTRACT Recent earthquakes off the northeastern Kamchatka coast reveal that this region is seismically active, although details of the locations and complexity of the fault system are lacking. The northern part of Kamchatka has poor coverage by permanent seismic stations and ground geodetic instruments. Here, we exploit the Differential Interferometric Synthetic Aperture Radar (DInSAR) technique to characterize the fault geometry and kinematics associated with the 29 March 2017 Mw 6.6 Yuzhno-Ozernovskoe earthquake. The aim is to contribute to identifying the active fault branches and to better understanding the complex tectonic regime in this region using the DInSAR technique, which has never before been applied to the analysis of coseismic offsets in Kamchatka. We produced coseismic deformation maps using Advanced Land Observation Satellite-2 ascending and descending and Sentinel-1A descending Synthetic Aperture Radar (SAR) scenes and detected a predominant uplift up to 20 cm and a westward motion of approximately 7 cm near the shoreline. We jointly inverted the three geodetic datasets using elastic half-space fault modeling to retrieve source geometry and fault kinematics. The best-fit solution for the nonlinear inversion suggests a north–west-dipping oblique reverse fault with right-lateral rupture. The model fault geometry is not only generally consistent with the seismic data but also reveals that a hitherto unknown fault was ruptured. The identified fault structure is interpreted as the northern extension of the east Kamchatka fault zone, implying that the region is more complex than previously thought. Important implications arise for the presence of unknown faults at the edges of subduction zones that can generate earthquakes with magnitudes greater than Mw 6.
5
Fan, Zi Li. "Main Controlling Factors of Hydrocarbon Accumulation at Different Phases: A Study on the Main Fault Depression Zones of Central H Basin." Applied Mechanics and Materials 733 (February 2015): 39–42. http://dx.doi.org/10.4028/www.scientific.net/amm.733.39.
Повний текст джерелаАнотація:
To understand the oil and gas accumulation rules and main controlling factors of H Basin at different phases, approaches such as reservoir dissection and analysis on the spatial allocation of reservoir accumulation conditions are adopted to divide the reservoir of the main fault depression zones of central H Basin into early and late phases. The widely-spread oil and gas at early phase are obviously more than that of the late phase. The main controlling factors of reservoir accumulation at early phase include source rocks area, antithetic faults - tilted upheavals and sand body of fan delta front subfacies while that of the late phase include sources rocks area, inverted structure and long-term developed fractures. The achievement of the study expounded in this paper is significantly important to correctly understand the oil and gas accumulation rules of complicated faulted-block fields and guide the oil and gas exploration activities.
6
Díaz, D., A. Maksymowicz, G. Vargas, E. Vera, E. Contreras-Reyes, and S. Rebolledo. "Exploring the shallow structure of the San Ramón thrust fault in Santiago, Chile (∼33.5° S), using active seismic and electric methods." Solid Earth Discussions 6, no. 1 (January 28, 2014): 339–75. http://dx.doi.org/10.5194/sed-6-339-2014.
Повний текст джерелаАнотація:
Abstract. The crustal-scale west-vergent San Ramón thrust fault system at the foot of the main Andean Cordillera in central Chile is a geologically active structure with Quaternary manifestations of complex surface rupture along fault segments in the eastern border of Santiago city. From the comparison of geophysical and geological observations, we assessed the subsurface structure pattern affecting sedimentary cover and rock-substratum topography across fault scarps, which is critic for evaluating structural modeling and associated seismic hazard along this kind of faults. We performed seismic profiles with an average length of 250 m, using an array of twenty-four geophones (GEODE), and 25 shots per profile, supporting high-resolution seismic tomography for interpreting impedance changes associated to deformed sedimentary cover. The recorded traveltime refractions and reflections were jointly inverted by using a 2-D tomographic approach, which resulted in variations across the scarp axis in both velocities and reflections interpreted as the sedimentary cover-rock substratum topography. Seismic anisotropy observed from tomographic profiles is consistent with sediment deformation triggered by west-vergent thrust tectonics along the fault. Electrical soundings crossing two fault scarps supported subsurface resistivity tomographic profiles, which revealed systematic differences between lower resistivity values in the hanging wall with respect to the footwall of the geological structure, clearly limited by well-defined east-dipping resistivity boundaries. The latter can be interpreted in terms of structurally driven fluid content-change between the hanging wall and the footwall of a permeability boundary associated with the San Ramón fault. The overall results are consistent with a west-vergent thrust structure dipping ∼55° E at subsurface levels in piedmont sediments, with local complexities being probably associated to fault surface rupture propagation, fault-splay and fault segment transfer zones.
7
Díaz, D., A. Maksymowicz, G. Vargas, E. Vera, E. Contreras-Reyes, and S. Rebolledo. "Exploring the shallow structure of the San Ramón thrust fault in Santiago, Chile (~33.5° S), using active seismic and electric methods." Solid Earth 5, no. 2 (August 26, 2014): 837–49. http://dx.doi.org/10.5194/se-5-837-2014.
Повний текст джерелаАнотація:
Abstract. The crustal-scale west-vergent San Ramón thrust fault system, which lies at the foot of the main Andean Cordillera in central Chile, is a geologically active structure with manifestations of late Quaternary complex surface rupture on fault segments along the eastern border of the city of Santiago. From the comparison of geophysical and geological observations, we assessed the subsurface structural pattern that affects the sedimentary cover and rock-substratum topography across fault scarps, which is critical for evaluating structural models and associated seismic hazard along the related faults. We performed seismic profiles with an average length of 250 m, using an array of 24 geophones (Geode), with 25 shots per profile, to produce high-resolution seismic tomography to aid in interpreting impedance changes associated with the deformed sedimentary cover. The recorded travel-time refractions and reflections were jointly inverted by using a 2-D tomographic approach, which resulted in variations across the scarp axis in both the velocities and the reflections that are interpreted as the sedimentary cover-rock substratum topography. Seismic anisotropy observed from tomographic profiles is consistent with sediment deformation triggered by west-vergent thrust tectonics along the fault. Electrical soundings crossing two fault scarps were used to construct subsurface resistivity tomographic profiles, which reveal systematic differences between lower resistivity values in the hanging wall with respect to the footwall of the geological structure, and clearly show well-defined east-dipping resistivity boundaries. These boundaries can be interpreted in terms of structurally driven fluid content change between the hanging wall and the footwall of the San Ramón fault. The overall results are consistent with a west-vergent thrust structure dipping ~55° E in the subsurface beneath the piedmont sediments, with local complexities likely associated with variations in fault surface rupture propagation, fault splays and fault segment transfer zones.
8
Barthwal, Himanshu, and Mirko van der Baan. "Passive seismic tomography using recorded microseismicity: Application to mining-induced seismicity." GEOPHYSICS 84, no. 1 (January 1, 2019): B41—B57. http://dx.doi.org/10.1190/geo2018-0076.1.
Повний текст джерелаАнотація:
Microseismicity is recorded during an underground mine development by a network of seven boreholes. After an initial preprocessing, 488 events are identified with a minimum of 12 P-wave arrival-time picks per event. We have developed a three-step approach for P-wave passive seismic tomography: (1) a probabilistic grid search algorithm for locating the events, (2) joint inversion for a 1D velocity model and event locations using absolute arrival times, and (3) double-difference tomography using reliable differential arrival times obtained from waveform crosscorrelation. The originally diffusive microseismic-event cloud tightens after tomography between depths of 0.45 and 0.5 km toward the center of the tunnel network. The geometry of the event clusters suggests occurrence on a planar geologic fault. The best-fitting plane has a strike of 164.7° north and dip angle of 55.0° toward the west. The study region has known faults striking in the north-northwest–south-southeast direction with a dip angle of 60°, but the relocated event clusters do not fall along any mapped fault. Based on the cluster geometry and the waveform similarity, we hypothesize that the microseismic events occur due to slips along an unmapped fault facilitated by the mining activity. The 3D velocity model we obtained from double-difference tomography indicates lateral velocity contrasts between depths of 0.4 and 0.5 km. We interpret the lateral velocity contrasts in terms of the altered rock types due to ore deposition. The known geotechnical zones in the mine indicate a good correlation with the inverted velocities. Thus, we conclude that passive seismic tomography using microseismic data could provide information beyond the excavation damaged zones and can act as an effective tool to complement geotechnical evaluations.
9
Lagabrielle, Yves, Riccardo Asti, Serge Fourcade, Benjamin Corre, Pierre Labaume, Jessica Uzel, Camille Clerc, Romain Lafay, and Suzanne Picazo. "Mantle exhumation at magma-poor passive continental margins. Part II: Tectonic and metasomatic evolution of large-displacement detachment faults preserved in a fossil distal margin domain (Saraillé lherzolites, northwestern Pyrenees, France)." BSGF - Earth Sciences Bulletin 190 (2019): 14. http://dx.doi.org/10.1051/bsgf/2019013.
Повний текст джерелаАнотація:
In two companion papers we report the detailed geological and mineralogical study of two emblematic serpentinized ultramafic bodies of the western North Pyrenean Zone (NPZ), the Urdach massif (paper 1) and the Saraillé massif (this paper). The peridotites have been uplifted to lower crustal levels during the Cretaceous rifting period in the future NPZ. They are associated with Mesozoic pre-rift metamorphic sediments and small units of thinned Paleozoic basement that were deformed during the mantle exhumation event. In the Saraillé massif, both the pre-rift cover and the thin Paleozoic crustal lenses are involved in a Pyrenean recumbent fold having the serpentinized peridotites in its core. Based on detailed geological cross-sections microscopic observations and microprobe mineralogical analyses, we describe the lithology of the two major extensional fault zones that accommodated: (i) the progressive uplift of the lherzolites upward the Cretaceous basin axis, (ii) the lateral extraction of the continental crust beneath the rift margins and, (iii) the decoupling of the pre-rift cover along the Upper Triassic (Keuper) evaporites and clays, allowing its gliding and conservation in the basin center. These two fault zones are the (lower) crust-mantle detachment and the (upper) cover décollement located respectively at the crust-mantle boundary and at the base to the detached pre-rift cover. The Saraillé peridotites were never exposed to the seafloor of the Cretaceous NPZ basins and always remained under a thin layer of crustal mylonites. Field constraints allow to reconstruct the strain pattern of the mantle rocks in the crust-mantle detachment. A 20–50 m thick layer of serpentinized lherzolites tectonic lenses separated by anastomosed shear zones is capped by a thin upper damage zone made up of strongly sheared talc-chlorite schists invaded by pyrite crystallization. The cover décollement is a few decameter-thick fault zone resulting from the brecciation of Upper Triassic layers. It underwent strong metasomatic alteration in the greenschist facies, by multi-component fluids leading to the crystallization of quartz, dolomite, talc, Cr-rich chlorite, amphiboles, magnesite and pyrite. These data collectively allow to propose a reconstruction of the architecture and fluid-rock interaction history of the distal domain of the upper Cretaceous northern Iberia margin now inverted in the NPZ.
10
Zeng, Chunlin, Yuejin Zhou, Leiming Zhang, Donggui Mao, and Kexin Bai. "Study on overburden failure law and surrounding rock deformation control technology of mining through fault." PLOS ONE 17, no. 1 (January 24, 2022): e0262243. http://dx.doi.org/10.1371/journal.pone.0262243.
Повний текст джерелаАнотація:
In the mining process of working face, the additional stress generated by the fault changes the law of roadway deformation and failure as well as the law of overburden failure. Aiming at the influence of the fault in the mining process of working face, this study introduced the geological strength index (GSI) to analyze the stress distribution in the elastic-plastic zone of the surrounding rock of the roadway. And similar experiments under different engineering backgrounds were combined to study the characteristics of overburden movement and stress evolution. Based on the conclusions obtained, the roadway support scheme was designed. This study shows that, compared with ordinary mining, through-the-fault mining causes slippage and dislocation of the fault, the load of the overburden is transferred to both sides of the fault, and the stress near the fault accumulates abnormally. The “three zones” characteristics of the overburden movement disappear, the subsidence pattern is changed from "trapezoid" to "inverted triangle", and the influence distance of the advanced mining stress on the working face is extended from 20m to 30m. The instability range of roadway surrounding rock is exponentially correlated with the rupture degree of the surrounding rock. Through the introduction of GSI, the critical instability range of roadway surrounding rock is deduced to be 2.32m. According to the conclusion, the bolt length and roadway reinforced support length are redesigned. Engineering application shows that the deformation rate of the roadway within 60 days is controlled below 0.1~0.5mm/d, the deformation amount is controlled within 150mm, and the roadway deformation is controlled, which generally meets the requirements of use. The research results provide guidance and reference for similar roadway support.
11
Arthur, M. J. "The Cenozoic evolution of the Lundy Pull-Apart Basin into the Lundy Rhomb Horst." Geological Magazine 126, no. 2 (March 1989): 187–98. http://dx.doi.org/10.1017/s0016756800006324.
Повний текст джерелаАнотація:
AbstractThe NW–SE Cornubian fault zones (FZs) continue to southwest Wales, where they caused dextral offsets during the late Stephanian. A fault bounded area of Devonian–Carboniferous strata, intruded by the Tertiary Lundy Igneous Complex, forms the Lundy Rhomboid. It originated as the Lundy Rhomb Graben, created by 28–40 km of Tertiary sinistral strike–slip faulting along the left-stepping NW–SE Sticklepath–Lustleigh FZ (SLFZ). Tertiary sedimentation in the graben was accompanied by intrusion of the 2.5–4.0 km thick igneous complex into its basement. Sedimentation later spread beyond the graben to form a ‘steer's horns’ basin, of which the Stanley Bank and West Lundy basins are remnants. The strata of the rhomb graben and the ‘steer's horns’ basin constituted the perhaps 4 km deep Lundy Pull-Apart Basin. Subsequent relatively minor dextral faulting on the left-stepping SLFZ inverted the graben into the Lundy Rhomb Horst; the basement of the graben was uplifted ≮ 1–2 km (net) and exposed by erosion of the Tertiary strata. The pull-apart basin developed at the intersection of reactivated Hercynian NW–SE transform FZs, and E–W subduction zone thrusts. Cenozoic N–S tensional and compressional reactivations of the thrusts were respectively associated with transtensional development of the pull-apart basin, transpressional of the rhomb horst.
12
Lamb, Simon. "The relation between short- and long-term deformation in actively deforming plate boundary zones." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 379, no. 2193 (February 2021): 20190414. http://dx.doi.org/10.1098/rsta.2019.0414.
Повний текст джерелаАнотація:
Satellite-based measuring systems are making it possible to monitor deformation of the Earth's surface at a high spatial resolution over periods of several decades and a significant fraction of the seismic cycle. It is widely assumed that this short-term deformation directly reflects the long-term pattern of crustal deformation, although modified in detail by local elastic effects related to locking on individual faults. This way, short-term deformation is often jointly inverted with long-term estimates of fault slip rates, or even stress, over periods of 10 s to 100 s kyrs. Here, I examine the relation between these two timescales of deformation for subduction, continental shortening and rifting tectonic settings, with examples from the active New Zealand and Central Andean plate boundary zone. I show that the relation is inherently non-unique, and simple models of locking on a deep-seated megathrust or decollement, or mantle flow, provide excellent fits to the short-term observations without requiring any information about the geometry and rate of surface faulting. The short-term deformation, in these settings at least, cannot be used to determine the behaviour of individual faults, but instead places constraints on the forces that drive deformation. Thus, there is a fundamental difference between the stress loading and stress relief parts of the earthquake cycle, with failure determined by dynamical rather than kinematic constraints; the same stress loading can give rise to widely different modes of long-term deformation, depending on the strength and rheology of the deforming zone, and the role of gravitational stresses. The process of slip on networks of active faults may have an intermediate timescale of kyrs to 10 s kyrs, where individual faults fail piecemeal without any characteristic behaviour. Physics-based dynamical models of short-term deformation may be the best way to make full use of the increasing quality of this type of data in the future. This article is part of a discussion meeting issue ‘Understanding earthquakes using the geological record’.
13
Brew, Graham, Muawia Barazangi, Ahmad Khaled Al-Maleh, and Tarif Sawaf. "Tectonic and Geologic Evolution of Syria." GeoArabia 6, no. 4 (October 1, 2001): 573–616. http://dx.doi.org/10.2113/geoarabia0604573a.
Повний текст джерелаАнотація:
ABSTRACT Using extensive surface and subsurface data, we have synthesized the Phanerozoic tectonic and geologic evolution of Syria that has important implications for eastern Mediterranean tectonic studies and the strategies for hydrocarbon exploration. Syrian tectonic deformation is focused in four major zones that have been repeatedly reactivated throughout the Phanerozoic in response to movement on nearby plate boundaries. They are the Palmyride Mountains, the Euphrates Fault System, the Abd el Aziz-Sinjar uplifts, and the Dead Sea Fault System. The Palmyrides include the SW Palmyride fold and thrust belt and two inverted sub-basins that are now the Bilas and Bishri blocks. The Euphrates Fault System and Abd el Aziz-Sinjar grabens in eastern Syria are large extensional features with a more recent history of Neogene compression and partial inversion. The Dead Sea transform plate boundary cuts through western Syria and has associated pull-apart basins. The geological history of Syria has been reconstructed by combining the interpreted geologic history of these zones with tectonic and lithostratigraphic analyses from the remainder of the country. Specific deformation episodes were penecontemporaneous with regional-scale plate-tectonic events. Following a relatively quiescent early Paleozoic shelf environment, the NE-trending Palmyride/Sinjar Trough formed across central Syria in response to regional compression followed by Permian-Triassic opening of the Neo-Tethys Ocean and the eastern Mediterranean. This continued with carbonate deposition in the Mesozoic. Late Cretaceous tectonism was dominated by extension in the Euphrates Fault System and Abd el Aziz-Sinjar Graben in eastern Syria associated with the closing of the Neo-Tethys. Repeated collisions along the northern Arabian margin from the Late Cretaceous to the Late Miocene caused platform-wide compression. This led to the structural inversion and horizontal shortening of the Palmyride Trough and Abd el Aziz-Sinjar Graben.
14
Baltazar, Orivaldo Ferreira, and Lydia Maria Lobato. "Structural Evolution of the Rio das Velhas Greenstone Belt, Quadrilátero Ferrífero, Brazil: Influence of Proterozoic Orogenies on Its Western Archean Gold Deposits." Minerals 10, no. 11 (November 4, 2020): 983. http://dx.doi.org/10.3390/min10110983.
Повний текст джерелаАнотація:
The Quadrilátero Ferrífero region is located in the extreme southeast of the Brasiliano São Francisco craton, Minas Gerais state, Brazil. It is composed of (i) Archean TTG granite-gneaissic terranes; (ii) the Archean Rio das Velhas greenstone belt; (iii) the Proterozoic metasedimentary and metavolcano-sedimentary covers. The Rio das Velhas rocks were deposited in the synformal NW–SE-directed Nova Lima basin. The Archean deformation converted the Nova Lima basin into an ample synclinorium with an eastern inverted flank. Archean orogenic gold mineralization within the Rio das Velhas greenstone belt rocks is controlled by NNW–SSE-directed, Archean regional shear zones subparallel to the strata of the Nova Lima synclinorium borders. Transamazonian and Brasiliano orogenies are superposed onto the Archean structures that control gold mineralization. In the eastern domain, Brasiliano fold-and-fault belts prevail, whereas in the western domain Archean and Transamazonian structures abound. The present study focus mainly is the western domain where the Cuiabá, Morro Velho, Raposos, Lamego and Faria deposits are located. Gold orebodies plunge to the E–NE and are tectonically controlled by the Archean D1–D2 deformation. The D3 Transamazonian compression—Which had a SE–NW vector sub-parallel to the regional mineralized Archean foliation/bedding—Buckled these structures, resulting in commonly open, synformal and antiformal regional folds. These are well documented near the gold deposits, with NE–SW axial traces and fold axes plunging to E–NE. Such folds are normal to inverted, NW-verging, with an axial planar foliation dipping moderately to the SE. The Transamazonian compression has only been responsible for the reorientation of the mineralized Archean gold ores, due to coaxial refolding characterized by an opposite tectonic transport. It has therefore not caused any other significant changes. Thrust shear zones, sub-parallel to the strong Transamazonian foliation, have given rise to localized metric segmentation and to the dislocation of gold orebodies. Throughout the region, along the towns of Nova Lima to Sabará, structures pertaining to the Brasiliano Araçuaí orogeny are represented only by gentle folding and by a discrete, non-pervasive crenulation cleavage. Thrust-shear zones and small-scale normal faults have caused, at most, metric dislocations along N–S-oriented planes.
15
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.
Повний текст джерелаАнотація:
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.
16
Adriano, Leandro B., Paulo T. L. Menezes, and Alan S. Cunha. "Tectonic framework of the Barra de São João Graben, Campos Basin, Brazil: Insights from gravity data interpretation." Interpretation 2, no. 4 (November 1, 2014): SJ65—SJ74. http://dx.doi.org/10.1190/int-2014-0011.1.
Повний текст джерелаАнотація:
The Barra de São João Graben (BSJG), shallow water Campos Basin, is part of the Cenozoic rift system that runs parallel to the Brazilian continental margin. This system was formed in an event that caused the reactivation of the main Precambrian shear zones of southeastern Brazil in the Paleocene. We proposed a new structural framework of BSJG based on gravity data interpretation. Magnetic data, one available 2D seismic line, and a density well-log of a nearby well were used as constraints to our interpretation. To estimate the top of the basement structure, we separated the gravity effects of deep sources from the shallow basement (residual anomaly). Then, we performed a 2D modeling exercise, in which we kept fixed the basement topography and the density of the sediments, to estimate the density of the basement rocks. Next, we inverted the residual anomaly to recover the depth to the top of the basement. This interpretation strategy allowed the identification of a complex structural framework with three main fault systems: a northeast–southwest-trending normal fault system, a northwest–southeast-trending transfer fault system, and an east–west-trending transfer fault system. These trends divided the graben into several internal highs and lows. Our interpretation was corroborated by the magnetic anomalies. The existence of ultradense and strongly magnetized elongated bodies in the basement was interpreted as ophiolite bodies that were probably obducted by the time of the shutdown of the Proterozoic Adamastor Ocean.
17
He, Kefeng, Yangmao Wen, Caijun Xu, and Yingwen Zhao. "Fault Geometry and Slip Distribution of the 2021 Mw 7.4 Maduo, China, Earthquake Inferred from InSAR Measurements and Relocated Aftershocks." Seismological Research Letters 93, no. 1 (October 13, 2021): 8–20. http://dx.doi.org/10.1785/0220210204.
Повний текст джерелаАнотація:
Abstract A nearly 70 yr hiatus of major seismic activity in the central eastern Bayan Har block (BKB) ended on 22 May 2021, when a multislip-peak sinistral strike-slip earthquake struck western Maduo County, Qinghai. This earthquake, which ruptured the nearly 170 km long Kunlun Pass–Jiangcuo fault, is a rather unique event and offers a rare opportunity to probe the mechanical properties of the intraplate lithosphere of the central eastern BKB. Here, we inferred the fault geometry associated with the Maduo earthquake using Interferometric Synthetic Aperture Radar (InSAR), and relocated aftershocks and inverted the slip distribution through InSAR radar phases and range offsets. Our analysis revealed that the geometry of the fault varies along the strike: the southeastern end of the fault dips steeply to the northeast, whereas the northwestern end dips southwestward. Using the combined datasets to constrain a coseismic slip, we found that the 2021 Maduo event was dominated by sinistral strike-slip movement, with a slight normal-slip component at a shallow depth, rupturing the steep-dipping fault for nearly 170 km in length. Five asperities were detected along the fault strike in the shallow crust (0–12 km) with a peak slip of ∼4.2 m corresponding mostly to simple structures, namely, continuous and straight rupture segments, suggesting that the rupture propagated across geometrical barriers in a multiasperity way. Based on an analysis of the strain field and the focal mechanisms of both the 2021 Maduo earthquake and historical earthquakes that have occurred in the BKB, we propose that the fault zones within the BKB can also generate large earthquakes and have the ability to accommodate the ongoing eastward and northeastward penetration of the Indian plate into the Eurasian plate.
18
Dooley, Tim P., and Michael R. Hudec. "Extension and inversion of salt-bearing rift systems." Solid Earth 11, no. 4 (July 6, 2020): 1187–204. http://dx.doi.org/10.5194/se-11-1187-2020.
Повний текст джерелаАнотація:
Abstract. We used physical models to investigate the structural evolution of segmented extensional rifts containing syn-rift evaporites and their subsequent inversion. An early stage of extension generated structural topography consisting of a series of en-échelon graben. Our salt analog filled these graben and the surroundings before continued extension and, finally, inversion. During post-salt extension, deformation in the subsalt section remained focused on the graben-bounding fault systems, whereas deformation in suprasalt sediments was mostly detached, forming a sigmoidal extensional minibasin system across the original segmented graben array. Little brittle deformation was observed in the post-salt section. Sedimentary loading from the minibasins drove salt up onto the footwalls of the subsalt faults, forming diapirs and salt-ridge networks on the intra-rift high blocks. Salt remobilization and expulsion from beneath the extensional minibasins was enhanced along and up the major relay or transfer zones that separated the original sub-salt grabens, forming major diapirs in these locations. Inversion of this salt-bearing rift system produced strongly decoupled shortening belts in basement and suprasalt sequences. Suprasalt deformation geometries and orientations are strongly controlled by the salt diapir and ridge network produced during extension and subsequent downbuilding. Thrusts are typically localized at minibasin margins where the overburden was thinnest, and salt had risen diapirically on the horst blocks. In the subsalt section, shortening strongly inverted sub-salt grabens, which uplifted the suprasalt minibasins. New pop-up structures also formed in the subsalt section. Primary welds formed as suprasalt minibasins touched down onto inverted graben. Model geometries compare favorably to natural examples such as those in the Moroccan High Atlas.
19
Beamish, David. "Deep resistivity imaging across the Northern and Central belts of the Southern Uplands." Geological Magazine 132, no. 5 (September 1995): 531–38. http://dx.doi.org/10.1017/s0016756800021191.
Повний текст джерелаАнотація:
AbstractMagnetotelluric data from 16 soundings have provided a northwest-southeast traverse across the Northern and Central belts of the Southern Uplands. The 34 km profile extends from the Ordovician Portpatrick Formation (northwest of the Thornhill Basin) across the Silurian Gala Group onto the Permian Lochmaben Basin in the southeast. The survey traverses, and has particular relevance to, the Ordovician/Silurian boundary (Orlock Bridge Fault), the associated Moniaive Shear Zone, and the Moffat Valley Lineament. The data obtained have been successfully modelled (inverted) to provide a crustal-scale resistivity cross-section. The two Upper Palaeozoic basins are resolved as relatively conducting features. Basin depths are about 200 m (Thornhill) and 1100 m (Lochmaben). Elsewhere, through the upper crustal interval, resistivities over 500 ohm m are associated with the Lower Palaeozoic greywackes. The Silurian formations appear more resistive (and slightly thicker) than their Ordovician counterparts. Depth to basement (base Lower Palaeozoic) is not a well-resolved characteristic but resistivity gradients observed below 5 km suggest a depth of this order. Concealed beneath the Thornhill Basin lie two narrow, vertical, conductive zones. The more substantial feature lies towards the northwest margin of the basin, and is probably associated with the Orlock Bridge Fault. The second zone lies towards the southeast margin of the basin. The conductivity minima, in both cases, are located in the depth range 2 to 3 km; they are separate and distinct from the overlying basin sediments. If the two anomalies, some 5 to 6 km apart, can be considered an expression of the Moniaive Shear Zone, then the major conductive constituents are concentrated at the margins. Two dipping, resistive features in the upper kilometre are imaged in the vicinity of the Moffat Valley Lineament.
20
Tricart, Pierre, Stephane Schwartz, Christian Sue, Gerard Poupeau, and Jean-Marc Lardeaux. "La denudation tectonique de la zone ultradauphinoise et l'inversion du front brianconnais au sud-est du Pelvoux (Alpes occidentales); une dynamique miocene a actuelle." Bulletin de la Société Géologique de France 172, no. 1 (January 1, 2001): 49–58. http://dx.doi.org/10.2113/172.1.49.
Повний текст джерелаАнотація:
Abstract In the western Alps, to the southeast of the Pelvoux massif (Champsaur-Embrunais-Brianconnais-Queyras transect), the Brianconnais zone consists of the southern tip of the Zone Houillere and small nappes of Mesozoic sediments, emplaced during the Eocene in HP-LT metamorphic conditions. During the Oligocene this tectonic pile was thrusted onto a late Eocene to early Oligocene flexural basin, deformed in low grade metamorphic conditions and belonging to the Ultradauphine zone. This major thrust, called here CBF [Chevauchement Brianconnais Frontal: Tricart 1986] represents the boundary between the external and the internal zones of the western Alps. It contains thin tectonic lenses of Subbrianconnais origin, so that the Brianconnais Front and the Penninic Front almost merge. Late Alpine extension. - We have recently discovered that the CBF was subsequently reactivated as an extensional detachment. This major negative inversion is associated with widespread extension in the internal (Brianconnais and Piemont) zones, resulting in multiscale normal faulting. Current field work in the Queyras area shows that this brittle multitrend extension is a continuation of the ductile extension that accompanied the exhumation of blue-schist bearing metamorphic units. Along the same transect, the external (Ultradauphine) zone was not affected by late-Alpine extension. This is still the present situation: to the east of the aseismic Pelvoux massif, the CBF bounds the Brianconnais seismic arc, the activity of which may be the continuation of the late-Alpine extension. At the scale of the western Alpine arc, active extensional-transtensional tectonics dominate in the internal zones while compressional uplift affects the external zone. In this contrasted stress field, the thrust-fault zone between internal and external arcs plays a major role of decoupling that can be demonstrated in several sites between the area analysed here and the Central Alps, including along the Ecors profile. Contribution of thermochronology. - In this paper, we compare apatite fission track (FT) ages from both sides of the inverted CBF to the southeast of the Pelvoux massif. In the hangingwall of the CBF, two ages were obtained from magmatic intrusions within the Zone houillere, close to Briancon. They are compared to recently published ages from the Champsaur Sandstones unit in the footwall of the CBF, along the same transect.
21
Yin, Xinxin, Xiaoyue Zhang, Run Cai, Haibo Wang, and Feng Liu. "Fast 1-D Velocity Optimization Inversion to 3D Velocity Imaging: A Case Study of Sichuan Maerkang Earthquake Swarm in 2022." Sustainability 14, no. 23 (November 29, 2022): 15909. http://dx.doi.org/10.3390/su142315909.
Повний текст джерелаАнотація:
To obtain an accurate one-dimensional velocity model, we developed the EA_VELEST method based on the evolutionary algorithm and the VELEST program. This method can quickly generate a suitable 1D velocity model and finally input it into the 3D velocity inversion process using the TomoDD method. We adopt TomoDD methods to inverse the high-resolution three-dimension velocity structure and relative earthquake hypocenters for this sequence. This system processing flow was applied to the Sichuan Maerkang earthquake swarm in 2022. By collecting the seismic phase data of the Maerkang area between 1 January 2009 and 15 June 2022, we relocated the historical earthquakes in the area and obtained accurate 3D velocity imaging results. The relocated hypocenters reveal a SE-trending secondary fault, which is located ~5 km NW of the Songgang fault. In the first ten-hour of the sequence, events clearly down-dip migrated toward the SE direction. The inverted velocity structure indicates that the majority of earthquakes during the sequence occurred along the boundaries of the high and low-velocity zones or high and low-VP/VS anomalies. Especially both the two largest earthquakes, MS 5.8 and MS 6.0, occurred at the discontinuities of high and low-velocity zones. The EA_VELEST method proposed in this paper is a novel method that has played a very good enlightenment role in the optimization of the one-dimensional velocity model in geophysics and has certain reference significance. The 3D velocity results obtained in this paper and the analysis of tectonic significance provide a reference for the seismogenic environment of this Maerkang earthquake and the deep 3D velocity of the Ganzi block.
22
Bailey, Adam H. E., Rosalind C. King, Simon P. Holford, and Martin Hand. "Extending interpretations of natural fractures from the wellbore using 3D attributes: The Carnarvon Basin, Australia." Interpretation 4, no. 1 (February 1, 2016): SB107—SB129. http://dx.doi.org/10.1190/int-2015-0113.1.
Повний текст джерелаАнотація:
Natural fractures can be identified in wellbores using electric resistivity image logs; however, the challenge of predicting fracture orientations, densities, and probable contribution to subsurface fluid flow away from the wellbore remains. Regional interpretations of fracture sets are generally confined to areas featuring an extensive reservoir analog outcrop. We have made use of extensive data sets available in Western Australia’s Northern Carnarvon Basin to map subsurface natural fractures, contributing to a regional understanding of fracture sets that can be applied to broader parts of the basin. The Northern Carnarvon Basin is composed of distinct structural domains that have experienced differing tectonic histories. Interpretation of regional fractures was achieved through an integrated approach, incorporating electric resistivity image logs from 52 Carnarvon Basin wells and seismic attribute analysis of two 3D seismic data sets: Bonaventure_3D ([Formula: see text]) and HC_93_3D ([Formula: see text]). Integration of these two data sets allows for a regionally extensive identification of natural fractures away from well control. Fractures of differing age and character are identified within the basin: Outboard areas are dominated by fractures likely to be open to fluid flow that are parallel to subparallel to the approximately east–west present-day maximum horizontal stress, providing possible flow conduits between potential damage zones identified alongside the north–northeast/south–southwest-striking faults that constitute the major structural trend of the basin, and inboard areas dominated by northeast–southwest to north–northeast/south–southeast fractures formed in fault damage-zones alongside normal, and inverted-normal, faults at those orientations. Finally, fractures observed in wells from the Rankin Platform and Dampier Subbasin occur at neither of these orientations; rather, they closely parallel the strikes of local faults. Additionally, variation is seen in fracture strikes due to isotropic present-day stress magnitudes. This methodology extends fracture interpretations from the wellbore and throughout the region of interest, constituting a regional understanding of fracture sets that can be applied to broader parts of the basin.
23
Todd, S. P. "Structure of the Dingle Peninsula, SW Ireland: evidence for the nature and timing of Caledonian, Acadian and Variscan tectonics." Geological Magazine 152, no. 2 (July 17, 2014): 242–68. http://dx.doi.org/10.1017/s0016756814000260.
Повний текст джерелаАнотація:
AbstractThe Palaeozoic rocks of the Dingle Peninsula provide a record of the evolution of the Caledonides, Acadides and Variscides. The succession ranges from Early Ordovician deep-water sediments, through Silurian shallow marine to non-marine sediments and volcanic rocks to an Old Red Sandstone (ORS) succession topped by Carboniferous marine shales. Comparison of structural styles in the unconformity-bounded groups, together with a detailed analysis of fault zones, allows the tectonic history to be deduced. The older rocks record Caledonian processes on the margin of Avalonia during Early Ordovician time and convergence then soft collision with Laurentia during Silurian time. The Dingle Basin was developed during the late Silurian – Early Devonian transtension in the Iapetus suture zone and was inverted in the latest Emsian Acadian orogenic episode. Post-Dingle Group ORS groups in the north of the peninsula were deposited in a syn-rift footwall block to the main Munster Basin. The Acadian transpressional and Munster Basin extensional structures were reactivated or overprinted in the Variscan deformation such that Acadian folds are transected by Variscan cleavage in both plan and vertical views. After Iapetus closure, changes in the tectonic regime are believed to be a result of adjustments in the geometry of subduction of the Rheic Ocean.
24
Acevedo, Jorge, Gabriela Fernández-Viejo, Sergio Llana-Fúnez, Carlos López-Fernández, and Javier Olona. "Ambient noise tomography of the southern sector of the Cantabrian Mountains, NW Spain." Geophysical Journal International 219, no. 1 (July 8, 2019): 479–95. http://dx.doi.org/10.1093/gji/ggz308.
Повний текст джерелаАнотація:
SUMMARY This study presents the first detailed analysis of ambient noise tomography in an area of the continental upper crust in the Cantabrian Mountains (NW Spain), where a confluence of crustal scale faults occurs at depth. Ambient noise data from two different seismic networks have been analysed. In one side, a 10-short-period station network was set recording continuously for 19 months. A second set of data from 13 broad-band stations was used to extend at depth the models. The phase cross-correlation processing technique was used to compute in total more than 34 000 cross-correlations from 123 station pairs. The empirical Green's functions were obtained by applying the time–frequency, phase-weighted stacking methodology and provided the emergence of Rayleigh waves. After measuring group velocities, Rayleigh-wave group velocity tomographic maps were computed at different periods and then they were inverted in order to calculate S-wave velocities as a function of depth, reaching the first 12 km of the crust. The results show that shallow velocity patterns are dominated by geological features that can be observed at the surface, particularly bedding and/or lithology and fracturing associated with faults. In contrast, velocity patterns below 4 km depth seem to be segmented by large structures, which show a velocity reduction along fault zones. The best example is the visualization in the tomography of the frontal thrust of the Cantabrian Mountains at depth, which places higher velocity Palaeozoic rocks over Cenozoic sediments of the foreland Duero basin. One of the major findings in the tomographic images is the reduction of seismic velocities above the area in the crust where one seismicity cluster is nucleated within the otherwise quiet seismic area of the range. The noise tomography reveals itself as a valuable technique to identify shear zones associated with crustal scale fractures and hence, lower strain areas favourable to seismicity.
25
Lagabrielle, Yves, Riccardo Asti, Serge Fourcade, Benjamin Corre, Marc Poujol, Jessica Uzel, Pierre Labaume, et al. "Mantle exhumation at magma-poor passive continental margins. Part I. 3D architecture and metasomatic evolution of a fossil exhumed mantle domain (Urdach lherzolite, north-western Pyrenees, France)." BSGF - Earth Sciences Bulletin 190 (2019): 8. http://dx.doi.org/10.1051/bsgf/2019007.
Повний текст джерелаАнотація:
In two companion papers, we report the detailed geological and mineralogical study of two emblematic serpentinized ultramafic bodies of the western North Pyrenean Zone (NPZ), the Urdach massif (this paper) and the Saraillé massif (paper 2). The peridotites have been exhumed to lower crustal levels during the Cretaceous rifting period in the future NPZ. They are associated with Mesozoic pre-rift metamorphic sediments and small units of thinned Paleozoic basement that were deformed during the mantle exhumation event. Based on detailed geological cross-sections and microprobe mineralogical analyses, we describe the lithology of the two major extensional fault zones that accommodated: (i) the progressive exhumation of the lherzolites along the Cretaceous basin axis; (ii) the lateral extraction of the continental crust beneath the rift shoulders and; (iii) the decoupling of the pre-rift cover along the Upper Triassic (Keuper) evaporites and clays, allowing its gliding and conservation in the basin center. These two fault zones are the (lower) crust-mantle detachment and the (upper) cover décollement located respectively at the crust-mantle boundary and at the base of the detached pre-rift cover. The Urdach peridotites were exposed to the seafloor during the Late Albian and underwent local pervasive carbonation and crystallization of calcite in a network of orthogonal veins (ophicalcites). The carbonated serpentinized peridotites were partly covered by debris-flows carrying fragments of both the ultramafics and Paleozoic crustal rocks now forming the polymictic Urdach breccia. The mantle rocks are involved in a Pyrenean overturned fold together with thin units of crustal mylonites. Continent-derived and mantle-derived fluids that circulated along the Urdach crust-mantle detachment led to the crystallization of abundant metasomatic rocks containing quartz, calcite, Cr-rich chlorites, Cr-rich white micas and pyrite. Two samples of metasomatized material from the crust-mantle detachment yielded in situ zircon U/Pb ages of 112.9 ± 1.6 Ma and 109.4 ± 1.2 Ma, thus confirming the Late Albian age of the metasomatic event. The cover décollement is a 30-m thick fault zone which also includes metasomatic rocks of greenschist facies, such as serpentine-calcite association and listvenites, indicating large-scale fluid-rock interactions implying both ultramafic and continental material. The lowermost pre-rift cover is generally missing along the cover décollement due to tectonic disruption during mantle exhumation and continental crust elision. Locally, metasomatized and strongly tectonized Triassic remnants are found as witnesses of the sole at the base of the detached pre-rift cover. We also report the discovery of a spherulitic alkaline lava flow emplaced over the exhumed mantle. These data collectively allow to propose a reconstruction of the architecture and fluid-rock interaction history of the distal domain of the upper Cretaceous northern Iberia margin now inverted in the NPZ.
26
Yu, Fusheng, Ruifeng Zhang, Jiafu Yu, Yidan Wang, Shuguang Chen, Jing Liu, Chenlin Wu, et al. "Meso-Cenozoic negative inversion model for the Linhe Depression of Hetao Basin, China." Geological Magazine 159, no. 4 (December 1, 2021): 535–60. http://dx.doi.org/10.1017/s0016756821001138.
Повний текст джерелаАнотація:
AbstractThe Linhe Depression is the largest tectonic unit in the Hetao Basin. The recently discovered commercial oil flow in the structural trap of wells JH2X and S5 has proved that the Meso-Cenozoic strata in the Linhe Depression have great exploration potential. Research on the kinematic model for the Mesozoic–Cenozoic Linhe Depression is important for analysing the geological conditions of hydrocarbon accumulation. In this study, field observations, seismic interpretation and scaled analogue modelling are performed. The results prove that the Linhe Depression experienced different stages of tectonic evolution, such as compressional depression (K1l), conversion from contraction to uniform subsidence (K1g), extensional rifting (E2–N2) and strike-slip deformation (Q), during the Mesozoic–Cenozoic eras. The kinematic model of negative inverted basins was first established with the early differential compression superimposed by the late extension. The seismic interpretation and analogue modelling results show that Jilantai Sag in the southern part of the Linhe Depression was subjected to compression from the Bayanwulashan fold–thrust belt on the NW side and the Helanshan fold–thrust belt on the SE side during Early Cretaceous time. Meanwhile, the Hanghou Sag in the northern part of the Linhe Depression was only compressed by the Langshan fold–thrust belt from the NW direction. The rifted structure generated by the extension from the SE direction during the Cenozoic Era resulted in the negative inversion of the pre-existing thrusts in different patterns. The intensity of negative inversion is controlled by several key factors, such as dip angle and the patterns of thrust faults, along with different basement textures. The morphological changes in the forebulge zone developed during Early Cretaceous time are responsible for the development of the segmented Central fault zones in the Hanghou Sag.
27
Basu, Urbi, and Christine A. Powell. "Velocity and azimuthal anisotropy structure underneath the Reelfoot Rift region from Rayleigh wave phase velocity dispersion curves." Geophysical Journal International 228, no. 1 (August 23, 2021): 291–307. http://dx.doi.org/10.1093/gji/ggab337.
Повний текст джерелаАнотація:
SUMMARY Phase velocity and azimuthal anisotropy maps for fundamental mode Rayleigh waves are determined for a portion of the central United States including the seismically active Reelfoot Rift (RFR) and the enigmatic Illinois Basin. Dense seismic array installations of the Northern Embayment Lithosphere Experiment, the EarthScope transportable array and the Ozarks Illinois Indiana Kentucky array allow a detailed investigation of phase velocity and anisotropy in a broad period range (20–100s).We obtain more than 12 000 well-constrained, unique two-station paths from teleseismic events. The two-station method is used to determine dispersion curves and these are inverted for isotropic phase velocity maps and azimuthal anisotropy maps for each period. The presence of fast phase velocities at lower crustal and uppermost mantle depths is found below the RFR, and Ste. Genevieve and Wabash Valley fault zones. At periods of 30s and higher, the RFR is underlain by slow phase velocities and is flanked to the NW and SE by regions of fast velocity. Fast phase velocities are present below the centre of the Illinois Basin in the period range 75–100s. Anisotropy fast axis orientations display complex patterns for each period and do not trend parallel to the direction of absolute plate motion. Anisotropy fast directions are consistently parallel to the trend of the RFR from 50s to higher periods, suggesting the presence of either frozen-in anisotropic fabric or fabric related to material transport from a recently discovered, pronounced low velocity zone below the Mississippi Embayment.
28
Nickschick, Tobias, Christina Flechsig, Jan Mrlina, Frank Oppermann, Felix Löbig, and Thomas Günther. "Large-scale electrical resistivity tomography in the Cheb Basin (Eger Rift) at an International Continental Drilling Program (ICDP) monitoring site to image fluid-related structures." Solid Earth 10, no. 6 (November 14, 2019): 1951–69. http://dx.doi.org/10.5194/se-10-1951-2019.
Повний текст джерелаАнотація:
Abstract. The Cheb Basin, a region of ongoing swarm earthquake activity in the western Czech Republic, is characterized by intense carbon dioxide degassing along two known fault zones – the N–S-striking Počatky–Plesná fault zone (PPZ) and the NW–SE-striking Mariánské Lázně fault zone (MLF). The fluid pathways for the ascending CO2 of mantle origin are one of the subjects of the International Continental Scientific Drilling Program (ICDP) project “Drilling the Eger Rift” in which several geophysical surveys are currently being carried out in this area to image the topmost hundreds of meters to assess the structural situation, as existing boreholes are not sufficiently deep to characterize it. As electrical resistivity is a sensitive parameter to the presence of conductive rock fractions as liquid fluids, clay minerals, and also metallic components, a large-scale dipole–dipole experiment using a special type of electric resistivity tomography (ERT) was carried out in June 2017 in order to image fluid-relevant structures. We used permanently placed data loggers for voltage measurements in conjunction with moving high-power current sources to generate sufficiently strong signals that could be detected all along the 6.5 km long profile with 100 and 150 m dipole spacings. After extensive processing of time series for voltage and current using a selective stacking approach, the pseudo-section is inverted, which results in a resistivity model that allows for reliable interpretations depths of up than 1000 m. The subsurface resistivity image reveals the deposition and transition of the overlying Neogene Vildštejn and Cypris formations, but it also shows a very conductive basement of phyllites and granites that can be attributed to high salinity or rock alteration by these fluids in the tectonically stressed basement. Distinct, narrow pathways for CO2 ascent are not observed with this kind of setup, which hints at wide degassing structures over several kilometers within the crust instead. We also observed gravity and GPS data along this profile in order to constrain ERT results. A gravity anomaly of ca. −9 mGal marks the deepest part of the Cheb Basin where the ERT profile indicates a large accumulation of conductive rocks, indicating a very deep weathering or alteration of the phyllitic basement due to the ascent of magmatic fluids such as CO2. We propose a conceptual model in which certain lithologic layers act as caps for the ascending fluids based on stratigraphic records and our results from this experiment, providing a basis for future drillings in the area aimed at studying and monitoring fluids.
29
Leborgne, Romain, Michael O. Rivett, Gift J. Wanangwa, Philippe Sentenac, and Robert M. Kalin. "True 2-D Resistivity Imaging from Vertical Electrical Soundings to Support More Sustainable Rural Water Supply Borehole Siting in Malawi." Applied Sciences 11, no. 3 (January 27, 2021): 1162. http://dx.doi.org/10.3390/app11031162.
Повний текст джерелаАнотація:
To improve borehole siting for rural water supply, an advanced resistivity method was adapted for developing country use and demonstrated in Malawi. The method was designed to be low cost, developing-country accessible, efficient. It allows single or multiple operators to acquire the multiple vertical electrical soundings (VESs) required that are inverted together in 2-D, to give a true cross-section of subsurface resistivity. Application at four sites generated true cross-sections of subsurface resistivity to around 100 m depth relevant to groundwater-resource investigation. A wide range of (hydro)geological features was identified, including fractured/weathered basement, gneiss domes, well-developed fault zones and several types of deltaic deposits. Imaging performance appears comparable to that of 2-D surface ERT (electrical resistivity tomography) that uses more expensive equipment, often unaffordable in developing countries. Based on the subsurface configurations determined and hydrogeological conceptualisation subsequently undertaken, the local aquifer potential could be evaluated, thereby providing a decision-making basis for future borehole siting at the sites surveyed. The technology is far superior to conventional 1-D VES, electromagnetic profiling or magnetic profiling currently used for borehole siting in Malawi. Technology adoption currently under consideration nationally would make use of existing VES capacity and permit much improved targeting of aquifer resource, more sustainable siting of boreholes and greater future resilience of Malawi’s rural water-supply infrastructure.
30
Ehteshami-Moinabadi, Mohsen. "Fault zone migration by footwall shortcut and recumbent folding along an inverted fault: example from the Mosha Fault, Central Alborz, Northern Iran." Canadian Journal of Earth Sciences 51, no. 9 (September 2014): 825–36. http://dx.doi.org/10.1139/cjes-2014-0001.
Повний текст джерелаАнотація:
The Mosha Fault is a multiply inverted fault in the Central Alborz. Field observations and structural data from this fault show that a footwall shortcut is the major mode of response of this fault to contractional deformation. Although the Mosha Fault is a basement-involved fault, there is no evidence of involvement of basement along its footwall shortcuts, at least in the study area. Footwall shortcuts along this fault vary in size from several hundreds of metres to tens of kilometres, suggesting that a footwall shortcut can be scale independent. It is proposed that footwall shortcuts can also occur as blind thrusts under fault-related folds in the terrains near the major inverted faults. Similar cases also exist in other regions such as Japan. Some large footwall shortcuts may be the causative fault of devastating earthquakes in the active inverted terrains such as the south Central Alborz. Incompetent layers acting as detachments may play an important role in the development of footwall shortcuts. Recumbent folding in the form of a cover nappe in the footwall of the Mosha Fault is another case of southward migration of deformation along the Mosha Fault by which the fault has responded to the Oligo-Miocene compression. This case can be considered as a newly recognized style of deforming structure that occurred along an inverted fault.
31
Beaudouin, Thierry, Oliver Bellier, and Michel Sebrier. "Present-day stress and deformation field within the Sulawesi Island area (Indonesia) : geodynamic implications." Bulletin de la Société Géologique de France 174, no. 3 (May 1, 2003): 305–17. http://dx.doi.org/10.2113/174.3.305.
Повний текст джерелаАнотація:
Abstract Sulawesi Island, eastern Indonesia, is located at the junction between the Pacific-Philippine, Indo-Australian Plates, and the Sunda Block, i.e., the southeastern edge of the Eurasian Plate (fig. 1). Its peculiar shape results from an on-going complex history of collision and rotation of continental slivers, island arcs, and oceanic domains with respect to the Sunda Block. Seismic network document a high level of seismicity in its northern boundaries, corresponding to deformation along the North Sulawesi trench and within the Molucca Sea subduction (fig. 1). Seismic activity is lower in central and south Sulawesi (fig. 4). It represents the activity of the NE, SW and SE arms thrust and the left-lateral Central Sulawesi Fault System, which comprises the Palu-Koro and Matano fault zones. This system connects, from northwest to southeast, the North Sulawesi Subduction zone to the Sorong fault (through th Sud Sula fault, after, Hinschberger et al. [2000] and the Tolo thrust in the North Banda Sea, Silver et al., [1983] proposed a deformation model that implies a clockwise rotation of the Sula block that is limited to the west and south by the Central Sulawesi Fault System. Paleomagnetic [Surmont et al., 1994] and GPS [Walpersdorf et al., 1998a] studies confirm and measure this rotation. In order to discus the present day kinematics and deformation of Sulawesi area, we performed a seismotectonic study, using focal mechanism of moderate and large (Mw ≥ 5) shallow earthquake (≤ 60 Km), collected from the Harverd CMT database (period 1976 to 2001) and complemented by Fitch [1972] and Cardwell [1980] (period 1964–1976). From these focal mechanisms and the known structural context, we defined ten homogeneous deformation domains (fig. 3 et fig.5). For seven of these, focal solution and moment tensors were inverted (Carey-Gailhardis and Mercier method [1987Carey-Gailhardis and Mercier method [1992]) and summed, in order to obtain stress and deformation tensors and rate estimates (Brune [1968] or Kostrov [1974] methods). Results are presented in table I, on figure 2 and figure 3. In northern Molucca Sea (north of equvator), the fast convergence slip rate (75 mm/a) is absorbed by the Sangihe subduction and accommodates the major part of the Philippines/Sunda plates motion. South of the equator, the estimated slip rate is only 2 mm/yr and represents the Sangihe slap subduction, which is affected by a torsion from NNE to E strike. Along the North-Sulawesi fault system, direction of the stress axes are not significantly different from east to west (average N356°±5E), but the determined slip rates increase from 20±4 mm/a to 54±10 mm/a, respectively. These values agree with the Sula block rotation pole previously proposed and located at the eastern extremity of the Northern Arm. The Palu-Koro fault, bounding the western Sula block, contributes to this rotaion because its trace fits well a small circle centered on the pole. However, seisicity document few moderate magnitude earthquake (fig. 4) related to the left lateral Central Sulawesi fault system, despite many identified active tectonic feature [Beaudouin, 1998]. Moreover, geologically determined Palu-Koro long-term slip rate of 35±8 mm/a, [Bellier et al., 2001] agrees with the far-field strike-slip rate of 32–45 mm/a proposed from GPS measurement [Walpersdorf et al., 1998b ; Stevens et al., 1999]. This confirms that is a fast slipping fault with a relatively low level of seismicity. The southeastern limit of the Sula block is represented by the ENE-trending Sorong strike-slip fault that extends from Irian-Jaya island to the east coast of Sulawesi where it connects to the Matano fault through the South Sula fault, This structure is particularly active south of the Sula island with a major Mw=7.7 earthquake (29/11/98). The inversion provides a strike-slip regime with respectively N220°E and N310°E-trending σ1. and σ3 stress axes. This study also highlight the Sula block internal deformation that could explain in the GPS velocities model obtained by walpersdorf et al. [1998a] for the Sula block rotation. We evidence an extensional stress regime with a N030°E-trending σ3, in the southern part of the Tomini Gulf. The estimated extension rate is 9 mm/a toward a N036°E direction. Considering the location of the Tomini Gulf, this deformation could be interpreted as a back-arc spreading related to the North Sulawesi subduction. The Batui zone correspond to the domain of the collision wich occured in the early-middle Plicene [e.g., Velleneuve et al., 2000] between the NE arm and the Irian-jaya derived Banggaï-Sula block. This domain remains active (12 earthquake with a major one of Mw=7.6, 14/05/00, fig. 4) but is mainly affected by strike-slip deformation. The Tolo thrust, lying off the SE arm east coast, absorbs the convergence to the west of the North Banda Sea, as attested by six moderate earthquake with reverse faulting focal mechanisms. This allows to distinguish a North-Banda block in SE Sulawesi, bounded by the South Sula segment of the Sorong fault, the Tolo thrust and the Hamilton fault (fig. 5) and moving westward at a lower rate than the Sula block. The SW arm of Sulawesi is also characterised by a compressional stress regime with N099°E-trending σ1 and an estimated convergence rate of 8.5 mm/a toward a N080°E direction. This is the consequence of the Majene-Kalosi thrust activity and could represent the most western accommodation of the Philippines/Sunda plates motion.
32
Perron, Paul, Michel Guiraud, Emmanuelle Vennin, Isabelle Moretti, Éric Portier, Laetitia Le Pourhiet, and Moussa Konaté. "Influence of basement heterogeneity on the architecture of low subsidence rate Paleozoic intracratonic basins (Reggane, Ahnet, Mouydir and Illizi basins, Hoggar Massif)." Solid Earth 9, no. 6 (November 7, 2018): 1239–75. http://dx.doi.org/10.5194/se-9-1239-2018.
Повний текст джерелаАнотація:
Abstract. The Paleozoic intracratonic North African Platform is characterized by an association of arches (ridges, domes, swells, or paleo-highs) and low subsidence rate syncline basins of different wavelengths (75–620 km). The Reggane, Ahnet, Mouydir and Illizi basins are successively delimited from east to west by the Amguid El Biod, Arak-Foum Belrem, and Azzel Matti arches. Through the analysis of new unpublished geological data (i.e., satellite images, well logs, seismic lines), the deposits associated with these arches and syncline basins exhibit thickness variations and facies changes ranging from continental to marine environments. The arches are characterized by thin amalgamated deposits with condensed and erosional surfaces, whereas the syncline basins exhibit thicker and well-preserved successions. In addition, the vertical facies succession evolves from thin Silurian to Givetian deposits into thick Upper Devonian sediments. Synsedimentary structures and major unconformities are related to several tectonic events such as the Cambrian–Ordovician extension, the Ordovician–Silurian glacial rebound, the Silurian–Devonian Caledonian extension/compression, the late Devonian extension/compression, and the Hercynian compression. Locally, deformation is characterized by near-vertical planar normal faults responsible for horst and graben structuring associated with folding during the Cambrian–Ordovician–Silurian period. These structures may have been inverted or reactivated during the Devonian (i.e., Caledonian, Mid–Late Devonian) compression and the Carboniferous (i.e., pre-Hercynian to Hercynian). Additionally, basement characterization from geological and geophysics data (aeromagnetic and gravity maps), shows an interesting age-dependent zonation of the terranes which are bounded by mega-shear zones within the arches–basins framework. The old terranes are situated under arches while the young terranes are located under the basins depocenter. This structural framework results from the accretion of Archean and Proterozoic terranes inherited from former orogeny (e.g., Pan-African orogeny 900–520 Ma). Therefore, the sedimentary infilling pattern and the nature of deformation result from the repeated slow Paleozoic reactivation of Precambrian terranes bounded by subvertical lithospheric fault systems. Alternating periods of tectonic quiescence and low-rate subsidence acceleration associated with extension and local inversion tectonics correspond to a succession of Paleozoic geodynamic events (i.e., far-field orogenic belt, glaciation).
33
Mahdi, Hayder A., Manal Sh Al-Kubaisi, and Samir Nouri Al-Jawad. "Structural Study of the Late Oligocene-Early Miocene Sequence in Khabaz Oil Field, NE of Iraq." Iraqi Geological Journal 55, no. 1F (June 30, 2022): 70–80. http://dx.doi.org/10.46717/igj.55.1f.6ms-2022-06-21.
Повний текст джерелаАнотація:
Khabaz Oil Field is located in Kirkuk, about 20 Km southwest of Kirkuk City between Jambour and Bai Hassan oil fields. Tectonically, it is located on the Unstable Shelf within the Low Folded Zone (Zagros Fold Belt). Six wells in Khabaz oil field with two seismic lines (Line K8 and KK54) are used to conduct the geometric analysis, which include the description of fold and fault systems for the purpose of understanding the structural setting of Jeribe (Early Miocene) and Azkand (Late Oligocene) formations in this field. Khabaz structure is a double plunging positively inverted subsurface asymmetrical anticline influence the whole pre-Holocene sedimentary sequence. The interlimb angle of this structure ranges between 137º to 151º which is classified as a gentle anticline. The dip values of the axial surface range between 82 – 84º, so it can be classified as an upright fold with a general trend NW-SE. The core of the anticline is bounded by two high angle dipping reverse fault splay dipping toward each other. These faults pushed the core of the anticline upward with respect to the limbs of the structure. The Southwestern limb is affected by several high angle inverted faults that were possibly bifurcated from one or two major faults. The Northeastern limb is also influenced by a series of high angle reverse, some are dipping toward the core of the structure and few others are dipping toward the limbs. Some of these faults especially those influenced the southwestern limb of the anticline were inherited from the original normal faults that bounding the graben structure developed during the deposition of the Shiranish Formation. During the Late Plio-Plistocene contraction phase, the sense of slip on these faults were inverted and the faults migrated upward into the Tertiary sequence resulting in the formation of the positively inverted structure.
34
Gunnels, Michael, Gurban Yetrimishli, Sabina Kazimova, and Eric Sandvol. "Seismotectonic evidence for subduction beneath the Eastern Greater Caucasus." Geophysical Journal International 224, no. 3 (November 5, 2020): 1825–34. http://dx.doi.org/10.1093/gji/ggaa522.
Повний текст джерелаАнотація:
SUMMARY We generated high-resolution 3-D seismic velocity models as well as a relocated earthquake catalogue across the eastern Greater Caucasus and Kura basins. This work was done using data from the recently upgraded Republic Seismological Survey Center's (RSSC) seismic network. We generated our tomographic images of crustal velocity structure in Azerbaijan using double-difference inversions (i.e. tomoDD and hypoDD). Earthquake catalogues from the RSSC between 2011 and 2016 were used; these catalogues include absolute arrival times of 103 288 P- and 120 952 S-wave traveltime picks for 7574 events recorded at 35 stations in Azerbaijan. Beginning with a layered, 1-D velocity model that was estimated using VELEST, we inverted simultaneously for relative location, Vp and Vs on a 3-D grid with dimensions 670 × 445 × 45 km, with a uniform grid spacing of 55 × 55 × 5 km for all of Azerbaijan. We observe that the relocated hypocentres cluster into two depth ranges, at the surface and at depth, that appear to correspond to major fault zones and the top of a subducting plate. Additionally, we note intermediate depth seismicity (∼50–60 km) beneath the Kura Basin, and a northward deepening of earthquake depths. Seismic velocities vary significantly throughout the study region; we observe very slow velocities throughout the Kura Basin between 5 and 15 km, and elevated velocities at 20–35 km. The wholesale velocity structure and seismic structure of Kura Basin strongly mirrors that of the Caspian Sea, which suggests that the geodynamics of the Caspian continue westwards into Azerbaijan. The key results of this study suggest that the northward subduction observed in the Caspian Sea continues beneath the Eastern Greater Caucasus, as well as provides evidence for active faulting along the southern margin of the mountain range.
35
Kovac, Peter, Luke Titus, Carlos Cevallos, and Josh Bluett. "Exploring for unconventional hydrocarbon plays in the Glyde Basin, Northern Territory, using FALCON® airborne gravity gradiometry (AGG) data." APPEA Journal 54, no. 2 (2014): 519. http://dx.doi.org/10.1071/aj13092.
Повний текст джерелаАнотація:
A FALCON® AGG and magnetic survey in the Glyde Sub-basin aims to define the structural pattern to identify unconventional hydrocarbon plays. The survey area consists of variable thick fluvial and lacustrine to shallow marginal marine carbonate-siliciclastic sequences and lesser volcanic rocks. The dominant tectonic feature identified on the AGG data is the Emu Fault Zone: a major structure of the central-southern part of the McArthur Basin. Seismic and surface geology suggest its overall sub-vertical strike-slip nature with positive flower structure geometry. In the north, a regional size pop-up structure, reverse, transpressional and strike-slip faults, and abundant synclines and anticlines identified in the AGG data indicate sinistral transpression. In the south, a transtensional segment of the Emu Fault Zone formed several regularly oriented, fault controlled depocentres. A geological cross-section across the Glyde Sub-basin supported by gravity modelling indicates a system of inverted transtensional faults. Offsets and bifurcations are common, forming local-scale transtensional or transpressional areas. The relationship between dolomitic carbonaceous siltstone, fault-related hydrothermal dolomite (HTD), and the tectonic pattern strongly suggests that the Emu Fault Zone controlled fluid migration and fault-related HTD deposition. Brecciated HTD reservoirs are best developed where a combination of strike-slip movement and extension allowed dolomitising and porosity-generating fluids to migrate along fracture networks, especially in transtensional pull-apart structures, and along the principal faults bounding elevated parts of the basement. This is consistent with the results of the Glyde–1 ST1 exploration well, which drilled 122 m of gas charged dolomitic breccia.
36
Hansen, Torsten Hundebøl, Ole Rønø Clausen, and Katrine Juul Andresen. "Thick- and thin-skinned basin inversion in the Danish Central Graben, North Sea – the role of deep evaporites and basement kinematics." Solid Earth 12, no. 8 (August 4, 2021): 1719–47. http://dx.doi.org/10.5194/se-12-1719-2021.
Повний текст джерелаАнотація:
Abstract. Using borehole-constrained 3D reflection seismic data, we analyse the importance of sub-salt, salt, and supra-salt deformation in controlling the geometries and the kinematics of inverted structures in the Danish Central Graben. The Danish Central Graben is part of the failed Late Jurassic North Sea rift. Later tectonic shortening caused mild basin inversion during the Late Cretaceous and Paleogene. Where mobile Zechstein evaporites are present, they have played a significant role in the structural evolution of the Danish Central Graben since the Triassic. Within the study area, Jurassic rifting generated two major W- to SW-dipping basement faults (the Coffee Soil Fault and the Gorm–Tyra Fault) with several kilometres of normal offset and associated block rotation. The Coffee Soil Fault system delineates the eastern boundary of the rift basins, and within its hanging wall a broad zone is characterized by late Mesozoic to early Paleogene shortening and relative uplift. Buttressed growth folds in the immediate hanging wall of the Coffee Soil Fault indicate thick-skinned inversion, i.e. coupled deformation between the basement and cover units. The western boundary of the inverted zone follows the westward pinch-out of the Zechstein salt. Here, thin-skinned folds and faults sole out into Zechstein units dipping into the half-graben. The most pronounced inversion structures occur directly above and in prolongation of salt anticlines and rollers that localized shortening in the cover above. With no physical links to underlying basement faults (if present), we balance thin-skinned shortening to the sub-salt basement via a triangle zone concept. This implies that thin Zechstein units on the dipping half-graben floor formed thrust detachments during inversion while basement shortening was mainly accommodated by reactivation of the major rift faults further east. Disseminated deformation (i.e. “ductile” at seismic scales) accounts for thin-skinned shortening of the cover units where such a detachment did not develop. The observed structural styles are discussed in relation to those found in other inverted basins in the North Sea Basin and to those produced from physical model experiments. Our results indicate that Zechstein units imposed a strong control on structural styles and kinematics not only during rift-related extension but also during basin inversion in large parts of the Danish Central Graben. Reactivated thin-skinned faults soling out into thin Triassic evaporite units within the carapace above Zechstein salt structures illustrate that even thin evaporite units may contribute to defining structures during tectonic extension and shortening. We thus provide an updated and dedicated case study of post-rift basin inversion, which takes into account the mechanical heterogeneity of sub-salt basement, salt, and supra-salt cover, including multiple evaporite units of which the Zechstein is the most important.
37
Mora, Andrés, and Mauricio Parra. "THE STRUCTURAL STYLE OF FOOTWALL SHORTCUTS ALONG THE EASTERN FOOTHILLS OF THE COLOMBIAN EASTERN CORDILLERA. DIFFERENCES WITH OTHER INVERSION RELATED STRUCTURES." CT&F - Ciencia, Tecnología y Futuro 3, no. 4 (December 31, 2008): 7–21. http://dx.doi.org/10.29047/01225383.460.
Повний текст джерелаАнотація:
For the first time we show geological evidence of unambiguosly documented footwall shortcuts adjacent to the trace of inverted master nomal faults, in the Eastern Cordillera of Colombia. The Eastern Cordillera is an orogen whose width and location are traced by a Mesozoic graben. However, few structures related with the graben have been documented up to the date. In this study we propose the Ariari-Guatiquía region as a type location for a unique observation of footwall shortcuts. The master normal faults in the Ariari-Guatiquia region, and documented in this manuscript, were active during the Lower Cretaceous, partially inverted during the Andean orogenesis (since the Oligocene at least) and active still nowadays. In the hangingwall basins of those master normal faults, like the Servitá fault, all the Cretaceous syn-rift sequence has been deposited and maximum paleo temperatures in the lowermost Cretaceous rocks are higher than those for the Zircon FT partial annealing zone (~250°C; 23,15 K). In contraction, the inverted master normal faults are high angle basement involved features that generated the main topographic contrast and exposing Lower Cretaceous units or older. In contrast, in the adjacent footwall shortcuts only part of the syn-rift Lower Cretaceous sequence was deposited or more commonly was not deposited at all. Maximum paletemperatures reached by the basal Cretaceous units exposed in the hanging wall blocks of the footwall shortcuts are always less than those of the Zircon FT partial annealing zone (~250°C; 23,15 K). Finally we use AFT data to document that the footwall shortcuts originated during the Late Miocene and later as shallowly dipping faults generating low elevation hanging wall areas. All the described features are present in the Ariari-Guatiquia region. However, northwards and along strike in the Eastern foothills there is a lot of partially analogue scenarios with respect to those described in the Ariari-Guatiquia region. Therefore we deduce that a similar structural segmentation should be present along the entire Eastern foothills of the Colombian Eastern Cordillera. Based on that we propose plausible candidates for master inverted normal faults and footwall shorcuts in other areas of the Eastern foothills.
38
Koehl, Jean-Baptiste P., Steffen G. Bergh, and Arthur G. Sylvester. "Tectonic evolution of the Indio Hills segment of the San Andreas fault in southern California, southwestern USA." Solid Earth 13, no. 8 (August 1, 2022): 1169–90. http://dx.doi.org/10.5194/se-13-1169-2022.
Повний текст джерелаАнотація:
Abstract. Transpressional uplift domains of inverted Pliocene–Pleistocene basin fill along the San Andreas fault zone in Coachella Valley, southern California (USA), are characterized by fault linkage and segmentation and deformation partitioning. The Indio Hills wedge-shaped uplift block is located in between two boundary fault strands, the Indio Hills fault to the northeast and the main San Andreas fault to the southwest, which merge to the southeast. Uplift commenced about or later than 0.76 million years ago and involved progressive fold and faulting stages caused by a change from distributed strain to partly partitioned right-slip and reverse/thrust displacement on the bounding faults when approaching the fault junction. Major fold structures in the study area include oblique, right-stepping, partly overturned en echelon macro-folds that tighten and bend into parallelism with the Indio Hills fault to the east and become more open towards the main San Andreas fault to the west, indicating an early and close relationship of the macro-folds with the Indio Hills fault and a late initiation of the main San Andreas fault. Sets of strike-slip to reverse step-over and right- and left-lateral cross faults and conjugate kink bands affect the entire uplifted area, and locally offset the en echelon macro-folds. Comparison with the Mecca Hills and Durmid Hills uplifts farther southeast along strike in Coachella Valley reveals notable similarities, but also differences in fault architectures, spatial and temporal evolution, and deformation mechanisms. The present work contributes to better understand the structure and tectonic history of a major fault system along a transform plate boundary.
39
Koehl, Jean-Baptiste P., Steffen G. Bergh, Tormod Henningsen, and Jan Inge Faleide. "Middle to Late Devonian–Carboniferous collapse basins on the Finnmark Platform and in the southwesternmost Nordkapp basin, SW Barents Sea." Solid Earth 9, no. 2 (March 28, 2018): 341–72. http://dx.doi.org/10.5194/se-9-341-2018.
Повний текст джерелаАнотація:
Abstract. The SW Barents Sea margin experienced a pulse of extensional deformation in the Middle–Late Devonian through the Carboniferous, after the Caledonian Orogeny terminated. These events marked the initial stages of formation of major offshore basins such as the Hammerfest and Nordkapp basins. We mapped and analyzed three major fault complexes, (i) the Måsøy Fault Complex, (ii) the Rolvsøya fault, and (iii) the Troms–Finnmark Fault Complex. We discuss the formation of the Måsøy Fault Complex as a possible extensional splay of an overall NE–SW-trending, NW-dipping, basement-seated Caledonian shear zone, the Sørøya–Ingøya shear zone, which was partly inverted during the collapse of the Caledonides and accommodated top–NW normal displacement in Middle to Late Devonian–Carboniferous times. The Troms–Finnmark Fault Complex displays a zigzag-shaped pattern of NNE–SSW- and ENE–WSW-trending extensional faults before it terminates to the north as a WNW–ESE-trending, NE-dipping normal fault that separates the southwesternmost Nordkapp basin in the northeast from the western Finnmark Platform and the Gjesvær Low in the southwest. The WNW–ESE-trending, margin-oblique segment of the Troms–Finnmark Fault Complex is considered to represent the offshore prolongation of a major Neoproterozoic fault complex, the Trollfjorden–Komagelva Fault Zone, which is made of WNW–ESE-trending, subvertical faults that crop out on the island of Magerøya in NW Finnmark. Our results suggest that the Trollfjorden–Komagelva Fault Zone dies out to the northwest before reaching the western Finnmark Platform. We propose an alternative model for the origin of the WNW–ESE-trending segment of the Troms–Finnmark Fault Complex as a possible hard-linked, accommodation cross fault that developed along the Sørøy–Ingøya shear zone. This brittle fault decoupled the western Finnmark Platform from the southwesternmost Nordkapp basin and merged with the Måsøy Fault Complex in Carboniferous times. Seismic data over the Gjesvær Low and southwesternmost Nordkapp basin show that the low-gravity anomaly observed in these areas may result from the presence of Middle to Upper Devonian sedimentary units resembling those in Middle Devonian, spoon-shaped, late- to post-orogenic collapse basins in western and mid-Norway. We propose a model for the formation of the southwesternmost Nordkapp basin and its counterpart Devonian basin in the Gjesvær Low by exhumation of narrow, ENE–WSW- to NE–SW-trending basement ridges along a bowed portion of the Sørøya-Ingøya shear zone in the Middle to Late Devonian–early Carboniferous. Exhumation may have involved part of a large-scale metamorphic core complex that potentially included the Lofoten Ridge, the West Troms Basement Complex and the Norsel High. Finally, we argue that the Sørøya–Ingøya shear zone truncated and decapitated the Trollfjorden–Komagelva Fault Zone during the Caledonian Orogeny and that the western continuation of the Trollfjorden–Komagelva Fault Zone was mostly eroded and potentially partly preserved in basement highs in the SW Barents Sea.
40
Qarbous, Abdelmounim, Fida Medina, and Christian Hoepffner. "Le bassin de Tizi n'Test (Haut Atlas, Maroc) : exemple d'évolution d'un segment oblique au rift de l'Atlantique central au Trias." Canadian Journal of Earth Sciences 40, no. 7 (July 1, 2003): 949–64. http://dx.doi.org/10.1139/e03-029.
Повний текст джерелаАнотація:
Detailed mapping completed by a microtectonic study of the Tizi n'Test Triassic basin, located along the Tizi n'Test fault zone in the Moroccan High Atlas, has allowed us to improve the knowledge on the geometry of the structures and the activity of faults during the Triassic extensional events related to the rifting of the central Atlantic. The latter are reflected by the development of a rift, at present inverted and deformed by the collision of Africa and Europe, comprising kilometric-scale grabens and half-grabens bounded by major faults trending ENEWSW, with a dip towards the NNW, and a dip-slip syndepositional motion. Inverse analysis of fault slickenside populations shows a heterogeneous Triassic state of stress. However, in the most significant measurement sites, the maximum horizontal stress σ1 is vertical, while the minimum stress σ3 is horizontal with a NWSE trend. The strike-slip component appears to be very small during the Triassic, a noticeable fact because of the obliquity of the basin with respect to the Atlantic rift.
41
Ford, M., and J. Vergés. "Evolution of a salt-rich transtensional rifted margin, eastern North Pyrenees, France." Journal of the Geological Society 178, no. 1 (September 4, 2020): jgs2019–157. http://dx.doi.org/10.1144/jgs2019-157.
Повний текст джерелаАнотація:
In this field study we reinterpret the narrow eastern North Pyrenean Zone, France, as an inverted salt-rich transtensional rift system based on identification of halokinetic depositional sequences across rift platform to distal rift margin domains with a cumulative throw of >2.8 km on steep Cretaceous faults. The rift platform records extension on detached rotational faults above Triassic evaporites from Jurassic to Aptian with uplift and erosion during the Albian. Transtensional Aptian–Albian minibasins align along the salt-rich rift margin fault zone. In the Aptian–Albian main rift large en echelon synclinal minibasins developed between salt walls, although Jurassic diapiric evolution is likely. Upper Cretaceous units locally record continuing diapirism. The Boucheville and Bas Agly depocentres, altered by synrift HT metamorphism, form the distal rift domain terminating south against the North Pyrenean Fault. The narrowness of the Pyrenean rift, shape of minibasins, en echelon oblique synclinal depocentres and folds coupled with a discontinuous distribution and intensity of HT metamorphism support a transtensional regime along the Iberia–Europe plate margin during late Early and early Late Cretaceous. In this model, the distal European margin comprises deep faults limiting laterally discontinuous crustal domains and ‘hot’ pull-apart basins with mantle rocks directly beneath sedimentary cover.Supplementary material: A table summarizing the stratigraphy of the NE Pyrenees and an interpreted Google Earth view of the Quillan syncline and minibasin are available at https://doi.org/10.6084/m9.figshare.c.5100036
42
Li, Aitang, Chaodi Xie, Yingfeng Ji, Weiling Zhu, Yan Xu, Guangming Wang, and Xiaoyan Zhao. "Stress Inversion and Fault Instability in the Source Region of the 2021 (MS 5.0) Yingjiang Earthquake." Applied Sciences 13, no. 2 (January 10, 2023): 957. http://dx.doi.org/10.3390/app13020957.
Повний текст джерелаАнотація:
On 12 June 2021, an earthquake with MS 5.0 occurred in Yingjiang, adjacent to eastern Myanmar, where seismic activity is frequent due to plate collision. To explore the mechanism of this earthquake, the regional stress field of the Yingjiang zone was inverted using the focal mechanisms of 187 historical earthquakes in this area. Furthermore, based on the obtained orientation of the principal stress axes and the stress shape ratio, the fault slip tendency (Ts) was also estimated to evaluate fault instability in the study area. The stress variation results show that the diffusion and migration of the aftershocks suggested strike–slip-type stress accumulation in Yingjiang with a principal compressive stress axis direction-oriented NNE‒SSW. Fault slip tendency results show that the seismogenic faults feature strikes within the ranges of 40~80° and 110~150° and dips of 60~90° and exhibit enhanced stress coupling. The distribution of the aftershock sequence is conjectured to have a high correlation with local fluid migration and was likely controlled by the hydrated rock-induced ruptures of the stressed fault systems near the source region. This study provides insights into potential earthquake risks in this region.
43
Loreto, Maria Filomena, Camilla Palmiotto, Filippo Muccini, Valentina Ferrante, and Nevio Zitellini. "Inverted Basins by Africa–Eurasia Convergence at the Southern Back-Arc Tyrrhenian Basin." Geosciences 11, no. 3 (March 4, 2021): 117. http://dx.doi.org/10.3390/geosciences11030117.
Повний текст джерелаАнотація:
The southern part of Tyrrhenian back-arc basin (NW Sicily), formed due to the rifting and spreading processes in back-arc setting, is currently undergoing contractional tectonics. The analysis of seismic reflection profiles integrated with bathymetry, magnetic data and seismicity allowed us to map a widespread contractional tectonics structures, such as positive flower structures, anticlines and inverted normal faults, which deform the sedimentary sequence of the intra-slope basins. Two main tectonic phases have been recognised: (i) a Pliocene extensional phase, active during the opening of the Vavilov Basin, which was responsible for the formation of elongated basins bounded by faulted continental blocks and controlled by the tear of subducting lithosphere; (ii) a contractional phase related to the Africa-Eurasia convergence coeval with the opening of the Marsili Basin during the Quaternary time. The lithospheric tear occurred along the Drepano paleo-STEP (Subduction-Transform-Edge-Propagator) fault, where the upwelling of mantle, intruding the continental crust, formed a ridge. Since Pliocene, most of the contractional deformation has been focused along this ridge, becoming a good candidate for a future subduction initiation zone.
44
Malz, Alexander, and Jonas Kley. "The Finne fault zone (central Germany): structural analysis of a partially inverted extensional fault zone by balanced cross-sections." International Journal of Earth Sciences 101, no. 8 (May 22, 2012): 2167–82. http://dx.doi.org/10.1007/s00531-012-0778-z.
Повний текст джерела
45
Qiao, Xin, Chunyan Qu, Xinjian Shan, Dezheng Zhao, and Lian Liu. "Interseismic Slip and Coupling along the Haiyuan Fault Zone Constrained by InSAR and GPS Measurements." Remote Sensing 13, no. 16 (August 23, 2021): 3333. http://dx.doi.org/10.3390/rs13163333.
Повний текст джерелаАнотація:
The Haiyuan fault zone is an important tectonic boundary and strong seismic activity belt in northeastern Tibet, but no major earthquake has occurred in the past ∼100 years, since the Haiyuan M8.5 event in 1920. The current state of strain accumulation and seismic potential along the fault zone have attracted significant attention. In this study, we obtained the interseismic deformation field along the Haiyuan fault zone using Envisat/ASAR data in the period 2003–2010, and inverted fault kinematic parameters including the long-term slip rate, locking degree and slip deficit distribution based on InSAR and GPS individually and jointly. The results show that there is near-surface creep in the Laohushan segment of about 19 km. The locking degree changes significantly along the strike with the western part reaching 17 km and the eastern part of 3–7 km. The long-term slip rate gradually decreases from west 4.7 mm/yr to east 2.0 mm/yr. As such, there is large strain accumulation along the western part of the fault and shallow creep along the Laohushan segment; while in the eastern section, the degree of strain accumulation is low, which suggests the rupture segments of the 1920 earthquake may have been not completely relocked.
46
Su, Sheng Rui, Ying Zhang, Hu Jun He, and Xiao Jian Wang. "Numerical Simulation on Forming Dynamics Mechanism and Stress State of Qianning Basin." Applied Mechanics and Materials 226-228 (November 2012): 1458–61. http://dx.doi.org/10.4028/www.scientific.net/amm.226-228.1458.
Повний текст джерелаАнотація:
Two-dimensional finite element model of Qianning basin was built on the basis of depth study on geological structure conditions and of rock mechanical properties in Qianning basin, tectonic stress field characteristics of Qianning fault belt and Qianning basin formation mechanism were inversed. The results show that: (1)A remarkable low stress region is come into being in the central part of Qianning basin, the low stress environment in the strike-slip fault zone has a very important control function for the basin formation. (2)in the rock bridge area of secondary fault belt sinistral right order, high stress concentration zone are formed, rock body subject to extrusion, which often forms pushing structure, the surface morphology appears landforms phenomenon such as surface uplift, drum kits etc.
47
Huang, Zicheng, Guohong Zhang, Xinjian Shan, Wenyu Gong, Yingfeng Zhang, and Yanchuan Li. "Co-Seismic Deformation and Fault Slip Model of the 2017 Mw 7.3 Darbandikhan, Iran–Iraq Earthquake Inferred from D-InSAR Measurements." Remote Sensing 11, no. 21 (October 28, 2019): 2521. http://dx.doi.org/10.3390/rs11212521.
Повний текст джерелаАнотація:
The 12 November 2017 Darbandikhan earthquake (Mw 7.3) occurred along the converence zone. Despite the extensive research on this earthquake, none of this work explained whether this earthquake rupture was limited to the thick sedimentary cover or it extends to the underlying crystalline basement rock (or both). Besides, whether this region will generate devastating earthquakes again and whether there is a one-to-one correlation between these anticlines and blind-reverse faults need further investigation. In this study, we derived the co-seismic interferograms from the Sentinel-1A/B data and successfully described the surface deformation of the main seismic zone. The fringe patterns of both the ascending and descending interferograms show that the co-seismic deformation is dominated by horizontal movements. Then, using the along- and across-track deformation fields of different orbits, we retrieved the three-dimensional deformation field, which suggests that the Darbandikhan earthquake may be a blind thrust fault close to the north–south direction. Finally, we inverted the geometrical parameters of the seismogenic fault and the slip distribution of the fault plane. The results show that the source fault has an average strike of 355.5° and a northeast dip angle of −17.5°. In addition, the Darbandikhan earthquake has an average rake of 135.5°, with the maximum slip of 4.5 m at 14.5 km depth. On the basis of the derived depth and the aftershock information provided by the Iranian Seismological Center, we inferred that this event primarily ruptured within the crystalline basement and the seismogenic fault is the Zagros Mountain Front Fault (MFF). The seismogenic region has both relatively low historical seismicity and convergent strain rate, which suggests that the vicinity of the epicenter may have absorbed the majority of the energy released by the convergence between the Arabian and the Eurasian plates and may generate Mw > 7 earthquakes again. Moreover, the Zagros front fold between the Lurestan Arc and the Kirkuk Embayment may be generated by the long-distance slippage of the uppermost sedimentary cover in response to the sudden shortening of the MFF basement. We thus conclude that the master blind thrust may control the generation of the Zagros front folding.
48
Song, Xiaogang, Yu Jiang, Xinjian Shan, Wenyu Gong, and Chunyan Qu. "A Fine Velocity and Strain Rate Field of Present-Day Crustal Motion of the Northeastern Tibetan Plateau Inverted Jointly by InSAR and GPS." Remote Sensing 11, no. 4 (February 20, 2019): 435. http://dx.doi.org/10.3390/rs11040435.
Повний текст джерелаАнотація:
Interferometric synthetic aperture radar (InSAR) data from 6 Envisat ASAR descending tracks; spanning the 2003–2010 period; was used to measure interseismic strain accumulation across the Northeastern Tibetan Plateau. Mean line-of-sight (LOS) ratemaps are computed by stacking atmospheric-corrected and orbital-corrected interferograms. The ratemaps from one track with different atmospheric-corrected results or two parallel; partially overlapping tracks; show a consistent pattern of left-lateral motion across the fault; which demonstrates the MERIS and ECMWF atmospheric correction works satisfactorily for small stain measurement of this region; even with a limited number of interferograms. By combining the measurements of InSAR and GPS; a fine crustal deformation velocity and strain rate field was estimated on discrete points with irregular density depending on the fault location; which revealed that the present-day slip rate on the Haiyuan fault system varies little from west to east. A change (2–3 mm/year) in line-of-sight (LOS) deformation rate across the fault is observed from the Jinqianghe segment to its eastern end. Inversion from the cross-fault InSAR profiles gave a shallow locking depth of 3–6 km on the main rupture of the 1920 earthquake. We therefore infer that the middle-lower part of the seismogenic layer on the 1920 rupture is not yet fully locked since the 1920 large earthquake. Benefit from high spatial resolution InSAR data; a low strain accumulation zone with high strain rates on its two ends was detected; which corresponds to the creeping segment; i.e., the Laohushan fault segment. Contrary to the previous knowledge of squeezing structure; an abnormal tension zone is disclosed from the direction map of principal stress; which is consistent with the recent geological study. The distribution of principal stress also showed that the expanding frontier of the northeastern plateau has crossed the Liupan Shan fault zone; even arrived at the northeast area of the Xiaoguan Shan. This result agrees with the deep seismic reflection profile.
49
Saetang, Kasemsak. "Focal Mechanisms of Mw 6.3 Aftershocks from Waveform Inversions, Phayao Fault Zone, Northern Thailand." International Journal of Geophysics 2017 (2017): 1–7. http://dx.doi.org/10.1155/2017/9059825.
Повний текст джерелаАнотація:
The focal mechanisms of Mw 6.3 aftershocks, Chiang Rai Province, Northern Thailand, were determined by using a multistation waveform inversion. Three aftershocks were selected and their waveforms were inverted for moment tensor calculation. Waveform inversions were derived from three broadband stations with three components and epicentral distances less than 250 km after all seismic stations were considered. The deviatoric moment tensor inversion was used for focal mechanism calculations. Band-pass filtering in the range of 0.03–0.15 Hz was selected for reducing low- and high-frequency noise. Source positions were created by using a single-source inversion and a grid-search method computed to optimize the waveform match. The results showed stable moment tensors and fault geometries with the southwest azimuth in the northern part of the Payao Fault Zone (PFZ) with depths shallower than 10 km. Left-lateral strike-slip with a reverse component was detected. The tectonics of the PFZ is constrained by fault-plane solutions of earthquakes. WSW directional strikes are observed in the northern part of the PFZ.
50
Zhu, Yifan, Tao Zheng, Minghao Wang, Hongcheng Zhao, and Xingguo Wang. "An Improved Directional Relay Adapted to a Distribution Network with IIG Integration." Energies 12, no. 17 (August 30, 2019): 3345. http://dx.doi.org/10.3390/en12173345.
Повний текст джерелаАнотація:
The integration of distributed generation (DG) into a distribution network changes the network’s topology. Three-stage current protection for a radial distribution network cannot meet the requirements of relay protection for a distribution network with DG. A directional relay that is based on the positive sequence fault component (PSFC) can effectively identify faults in the positive and negative directions and can be used to solve the adaptability problem with three-stage current protection in a multi-source distribution network. However, DG and the traditional generators have different fault characteristics and are affected by different control strategies, which may lower the sensitivity of a directional relay based on the PSFC or even cause mal-operation. Focusing on this problem, this paper proposes an improved directional relay that is adapted to a distribution network with inverter-interfaced generation (IIG) integration. The improved scheme divides the operation zone of the directional relay based on the PSFC into sensitive and insensitive areas. If the result of a phase comparison is located in the insensitive area, further identification is needed according to a comparison of the current amplitudes. Simulation experiments are carried out based on PSCAD/EMTDC, and their results verify the correctness of the proposed scheme.