The largest Tan-Lu active fault system in northeastern Asia,spans approximately 3500 km in length and varies in width from 10 km to 200 km.In 1668,an earthquake with a magnitude of 8.5 occurred in Tancheng,causing the...The largest Tan-Lu active fault system in northeastern Asia,spans approximately 3500 km in length and varies in width from 10 km to 200 km.In 1668,an earthquake with a magnitude of 8.5 occurred in Tancheng,causing the loss of over 50000 lives.To constrain the timing and process of the Tan-Lu fault system on eastern Asian margin,this study presents the field mapping,thin section observation,geochronology,and microanalysis of Weiyuanpu-Yehe ductile shear zone(WYSZ)of the northern Tan-Lu fault system.Kinematic indicators and microstructures suggest a sense of sinistral strike-slip.The deformation temperature of the mylonite is mediate to high based on the quartz deformation,c-axis fabrics.The differential stress of the shear zone is 20‒40 MPa using quartz paleopiezometry.The dikes within the shear zone yielded zircon U-Pb ages of 165‒163 Ma.However,due to the ambiguous geological relationship between the dikes and shear zone,additional geochronology is warranted.Since the Mesozoic era,based on the exposure of mylonite and dikes,the upper crust has been extensively eroded,exposing the ductile shear zone.Moreover,the understanding of the geometry and process of pre-existing structures has fundamental implications for predicating the potential earthquakes for the Tan-Lu fault system.展开更多
The Longmenshan structural belt on the eastern edge of the Tibetan Plateau experienced the impactful Mw7.92008 Wenchuan Earthquake,causing a 350 km surface rupture.Traditional models attribute this to the Beichuan and...The Longmenshan structural belt on the eastern edge of the Tibetan Plateau experienced the impactful Mw7.92008 Wenchuan Earthquake,causing a 350 km surface rupture.Traditional models attribute this to the Beichuan and Pengguan faults,but our research reveals a complex fault system at the northern end,with inconsistencies in surface rupture,aftershock distribution,and focal mechanisms.We integrate shallow geology,active source seismic reflection,and magnetotelluric profiling to establish a deep structural model for the northern end of the Longmenshan structural belt.This area exhibits dominant reverse thrust nappe tectonics,and analyzing the tectonic evolution history provides insights into deformation propagation from the orogenic belt toward the Sichuan Basin.Focal mechanism analysis and relocated aftershock data reveals two distinct types of seismogenic structures in the northern end of the Longmenshan structural belt.In the middle to northern segments,the reverse fault type is attributed to reactivated pre-existing faults.Conversely,at the northern end,the strike-slip fault type originates from high-angle co-seismic rupture cutting through pre-existing reverse faults.This study enhances our understanding of fault complexity and seismic mechanisms in the northeastern Longmenshan structural belt,providing new insights into regional tectonics.展开更多
The Palu segment,situated in the northeastern part of the East Anatolian Fault System(EAFS),is a crucial structural feature with notable seismic potential.This study examines the paleoseismic activity of the Palu segm...The Palu segment,situated in the northeastern part of the East Anatolian Fault System(EAFS),is a crucial structural feature with notable seismic potential.This study examines the paleoseismic activity of the Palu segment through trench excavations and geochronological analyses utilizing Optically Stimulated Luminescence(OSL)and radiocarbon(14C)dating methods.Two trenches,located near Karşıbahçeler,exposed evidence of multiple surface-rupturing seismic events spanning the Holocene and Pleistocene epochs.Chronological analyses identified five distinct seismic events in trench 1(P1),dated between 94.09±6.07 ka and 0.84±0.45 ka,and three events in trench 2(P2),dated between 28.83±1.61 ka and 351±21 BP.Bayesian analysis using Oxcal distribution suggested event timings between 90.52±25.99 ka and 1.25±0.55 ka.Comparative analysis with historical earthquake records correlates the most recent event with the 1789 or 1874 AD earthquakes,while the penultimate event matches the 995 AD earthquake.Earlier events reflect prehistoric tectonic activity.The recurrence intervals for these events range from 710 to 5,370 years during the Holocene,with evidence of seismic activity extending into the Pleistocene.Stress inversion analyses and geodetic data indicate a predominantly strike-slip stress regime,consistent with geometry of the fault.These findings provide critical insights into the long-term seismic behavior and recurrence patterns of the Palu segment,enhancing seismic hazard assessments for the region.展开更多
The Songliao Basin in northeast China is one of the largest petroliferous basins worldwide,and features the T_(2)fault system,which consists of numerous minor extensional normal faults.This study combines high-resolut...The Songliao Basin in northeast China is one of the largest petroliferous basins worldwide,and features the T_(2)fault system,which consists of numerous minor extensional normal faults.This study combines high-resolution 3D seismic datasets to detail the characteristics of the T_(2)fault system,contributing two key findings:(1)The T_(2)faults are confirmed as polygonal fault systems,characterized by closely spaced,layer-bounded faults with small throws,high dip angles,and random orientations,forming intricate polygonal networks.(2)The study reveals the influence of tectonic stresses on the fault system,showing spatial variations across different tectonic units.In depressions,T_(2)faults exhibit short lengths,small throws,high density,and multiple directions.In contrast,in inverted anticline belts,they have longer lengths,bigger throws,higher density,and concordant orientations.These variations demonstrate the impact of tectonic inversion on the development of T_(2)faults.The significance of this research lies in presenting a typical polygonal fault system developed in a deep lake succession and was superposed the influence by regional tectonic stress coeval with its development.The new insights facilitate a reevaluation of the T_(2)fault system's role in hydrocarbon migration and accumulation within the Songliao Basin.展开更多
Recent studies on the Xianshuihe-Xiaojiang fault system suggest that the Late Quaternary strike-slip rate is approximately uniform along the entire length of the fault zone, about 15±2 mm/a. This approximately un...Recent studies on the Xianshuihe-Xiaojiang fault system suggest that the Late Quaternary strike-slip rate is approximately uniform along the entire length of the fault zone, about 15±2 mm/a. This approximately uniform strike slip rate strongly supports the clockwise rotation model of the southeastern Tibetan crust. By approximating the geometry of the arc-shaped Xianshuihe-Xiaojiang fault system as a portion of a small circle on a spherical Earth, the 15±2 mm/a strike slip rate corresponds to clockwise rotation of the Southeastern Tibetan Block at the （5.2±0.7）×10^-7 deg/a angular velocity around the pole （21°N, 88°E） relative to the Northeast Tibetan Block. The approximately uniform strike slip rate along the Xianshuihe-Xiaojiang fault system also implies that the Longmeushan thrust zone is not active, or at least its activity has been very weak since the Late Quaternary. Moreover, the total offset along the Xiaushuihe-Xiaojiang fault system suggests that the lateral extrusion of the Southeastern Tibetan Block relative to Northeastern Tibetan Block is about 160 km and 200-240 km relative to the Tarim-North China block. This amount of lateral extrusion of the Tibetan crust should have accommodated about 13-24% convergence between India and Eurasia based on mass balance calculations. Assuming that the slip rate of 15±2 mm/a is constant throughout the entire history of the Xianshuihe-Xiaojiang fault system, 11±1.5 Ma is needed for the Xianshuihe-Xiaojiang fault system to attain the 160 km of total offset. This implies that left-slip faulting on the Xianshuihe-Xiaojiang fault system might start at 11±1.5 Ma.展开更多
The fault system of Liaodong Bay developed extensively under the control of the Tanlu Fault. The fault system can be grouped into strike-slip faults of grade Ⅰ, trunk faults of grade Ⅱand branch faults （induced fau...The fault system of Liaodong Bay developed extensively under the control of the Tanlu Fault. The fault system can be grouped into strike-slip faults of grade Ⅰ, trunk faults of grade Ⅱand branch faults （induced faults） of grade Ⅲ respectively based on its developmental scale. The faults of grade Ⅰ and Ⅱwere deep, early and large while the faults of grade Ⅲwere shallow, late and small. The formation, evolution and distribution features played a significant role in controlling the migration of oil and gas in both horizontal and vertical directions. The fluid transfer in the fault system occurred in the process of faulting. The strike-slip and trunk faults moved actively forming predominant pathways for oil and gas migration. The branch faults, with weak activity, generally controlled the development of traps and were beneficial for the accumulation and preservation of oil and gas. The faults of grade Ⅰ and Ⅱ formed the major migration pathways for oil and gas, but their fault activity rates appeared to vary along their strikes. The zones with a relatively low fault activity rate might be favorable for oil and gas accumulation. When the activities of strike-slip, trunk, and branch faults came to a halt, the fault seal behavior had a vitally important effect on the accumulation of oil and gas. The controlling role of the fault over fluid distribution was further analyzed by calculating the fault activity quantitatively.展开更多
This article aims to analyze the main controlling factors of development, distribution and evolution of the fault systems in the Tarim Basin. Based on the seismic profile interpretation, compre- hensive analysis of th...This article aims to analyze the main controlling factors of development, distribution and evolution of the fault systems in the Tarim Basin. Based on the seismic profile interpretation, compre- hensive analysis of the drilling and geologic data, six fault systems maybe recognized in the Tarim Basin, they are the foreland fault system of the South Tianshan Mountain, the northern Tarim uplift fault sys- tem, North Tarim depression fault system, central fault system, Southwest Tarim fault system, and Southeast Tarim fault system. It is indicated that the main differences exist at the development, evolu- tion and distribution of the fault systems in the Tarim Basin. The sub-fault systems can be recognized according to the differences of the fault development and distribution in the interior of the fault system. It is characterized that the multi-level differential development and distribution of the fault systems ex- ist in the Tarim Basin. The fault belt developed in the Paleozoic strata mainly distribute at the pa- leo-uplift and paleo-slope in the interior of the Tarim Basin, and the fault belt occurred in the Meso-Cenozoic beds mainly develop at the peripheral foreland depressions. Zonal and segment differ- ential development and distribution of the fault systems also exist in the Tarim Basin. The formation and distribution of the Tarim fault systems is of complex controlling mechanisms. Poly-phase structural movement and tectonic transition controls the multi-phase differential development and distribution of the fault systems in the Tarim Basin. Multi-level differential development and distribution is controlled by multi-level detachment belt and regional unconformities. Zonal and segment differential develop- ment and distribution of the Tarim fault systems maybe controlled by pre-existed basement structural texture. The major direction of the fault systems in the Tarim Basin is controlled by the later stage basin-mountain coupling.展开更多
Coulomb stress accumulation and releasing history and its relationship with the occur- rence of strong historical earthquakes could deepen our understanding of the occurrence pattern of strong earthquakes and hence it...Coulomb stress accumulation and releasing history and its relationship with the occur- rence of strong historical earthquakes could deepen our understanding of the occurrence pattern of strong earthquakes and hence its seismic potential in future. The sinistral strike-slip Xianshuihe- Xiaojiang fault zone （XXFS） is one of the most dangerous fault zones in China, extending 1 500-km- long from the central Tibetan Plateau to the Red River fault zone. There are 35 M≥6.5 historical earth- quakes occurred since 1327, hence it is an ideal site for studying the Coulomb stress evolution history and its relationship with the occurrences of strong earthquakes. In this study, we evaluated the Cou- lomb stress change history along the XXFS by synthesizing fault geometry, GPS data and historical earthquakes. Coulomb stress change history also revealed different patterns of historical earthquakes on different segments of the XXFS, such as characteristic recurrence intervals along the Salaha-Moxi fault and super-cycles along the Xianshuihe fault. Based on the occurrence pattern of past historical earthquakes and current Coulomb stress field obtained in this study, we suggest positive ACFS and hence high seismic potential along the Salaha-Moxi fault and the Anninghe fault.展开更多
The Bodong Sag,located in the Bohai Sea,offshore China,is one of the most petroliferous basins in China.Based on three dimensional seismic reflection data and time slice data,we analyze the fault system of the Bodong ...The Bodong Sag,located in the Bohai Sea,offshore China,is one of the most petroliferous basins in China.Based on three dimensional seismic reflection data and time slice data,we analyze the fault system of the Bodong area in detail,establish the fault structure pattern of different types and summarize the distribution of the fault system.It is concluded that the development characteristics of the Cenozoic fault system are in accordance with the dextral stress field of the Tanlu Fault,which displayed a brush structure with NNE strike-slip faults as its principal faults,NE-trending extensional faults as secondary faults and EW-trending faults as minor faults.Faults can be divided into （1） strike-slip type,（2） extensional type,（3） strike-slip extensional type and （4） extensional strike-slip type.The spatial structures of different faults have obvious differences because of the fault properties and activity intensity.The fault system at different stages shows tremendous differences because of the transition of the Tanlu Fault from sinistral strike-slip to dextral strike-slip,the transition between extension and strike-slip,and the transition from mantle upwelling to thermal subsidence.According to the controlling effect of faults on basin structure,the Cenozoic basin experienced four evolutionary stages,（a） transition stage from sinistral strike-slip to dextral strike-slip,（b） strike-slip extensional faulted stage,（c） extensional strike-slip faulted stage and （d） strike-slip depression stage.The identification of temporal and spatial differences of faults could be used as a significant guideline for oil and gas exploration in the Bodong area.展开更多
As one of the longest strike-slip fault in Asia,the Altyn Tagh Fault（ATF）defines the northern boundary of the Tibetan Plateau and plays a significant role inaccommodating the deformation resulting from the IndiaAsia...As one of the longest strike-slip fault in Asia,the Altyn Tagh Fault（ATF）defines the northern boundary of the Tibetan Plateau and plays a significant role inaccommodating the deformation resulting from the IndiaAsia convergence.展开更多
Gas injection serves as a main enhanced oil recovery(EOR)method in fractured-vuggy carbonate reservoir,but its effect differs among single wells and multi-well groups because of the diverse fractured-vuggy configurati...Gas injection serves as a main enhanced oil recovery(EOR)method in fractured-vuggy carbonate reservoir,but its effect differs among single wells and multi-well groups because of the diverse fractured-vuggy configuration.Many researchers conducted experiments for the observation of fluid flow and the evaluation of production performance,while most of their physical models were fabricated based on the probability distribution of fractures and caves in the reservoir.In this study,a two-dimensional physical model of the karst fault system was designed and fabricated based on the geological model of TK748 well group in the seventh block of the Tahe Oilfield.The fluid flow and production performance of primary gas flooding were discussed.Gas-assisted gravity flooding was firstly introduced to take full use of gas-oil gravity difference,and its feasibility in the karst fault system was examined.Experimental results showed that primary gas flooding created more flow paths and achieved a remarkable increment of oil recovery compared to water flooding.Gas injection at a lower location was recommended to delay gas breakthrough.Gas-assisted gravity flooding achieved more stable gas-displacing-oil because oil production was at a lower location,and thus,the oil recovery was further enhanced.展开更多
The Kangding City in eastern Tibet is at high risk due to frequent strong earthquakes along the Xianshuihe sinistral strike-slip fault bounding the Chuandian Block to the northeast.The knowledge of paleo-seismicity re...The Kangding City in eastern Tibet is at high risk due to frequent strong earthquakes along the Xianshuihe sinistral strike-slip fault bounding the Chuandian Block to the northeast.The knowledge of paleo-seismicity recurrence along this fault system is key to the evaluation of earthquake hazards in this region;thus,more accurate paleoseismic information are required.We examined the paleo-seismicity along the Zheduotang fault in the central segment of the Xianshuihe fault system by applying the field investigation,trenching,and Quaternary dating methods(e.g.,OSL and^(14)C).Field observations found~8.5 m offset of stream by sinistral slip along the Zheduotang fault.We trenched the central fault zone of the Zheduotang fault and found that the colluvial wedges and five buried,discontinuous,A-soil horizons progressively have been offset in the shallow graben on the SW-side of the main fault indicative of the paleo-earthquakes.The dating results of OSL and^(14)C,in line with existing data,enable us to establish the paleo-seismic history of the Zheduotang fault.It shows at least eight surface ruptures in the last 7500 years identified from displaced buried soils,colluvial wedges and terraces.Our study reveals~100 years minimum paleo-earthquake recurrence,suggesting potential large earthquakes in the Kangding area in the future.展开更多
The Bachu （巴楚） uplift is one of the most active tectonic regions nowadays in the Tarim basin, which is also a faulted block uplift that was intensively active during the Cenozoic. This study was based primarily on...The Bachu （巴楚） uplift is one of the most active tectonic regions nowadays in the Tarim basin, which is also a faulted block uplift that was intensively active during the Cenozoic. This study was based primarily on the geological structure interpretation of seismic profiles, applying the theories and methods of basin dynamics, structural analysis and tectono-stratigraphic analysis, the geometry and kinematics features of the fault systems in the Bachn uplift were analyzed in detail. Our study shows that each fault belt is mainly characterized by compression and overthrusting, most of the faults initiated and activated during the Mid-Late Himalayan period, and that the general structural styles of the Bachu uplift were basement-involved pop-up thrust faulted block uplift, of which the southern margin was covered by the large-scale decollement fault system. The basement-involved structures widely developed in the higher position of the basement uplift, while decollement fault system developed mainly at the position with gypsum mudstone. The evolution process of Bachu uplift included back-bulge slope of the peripheral foreland basin in Mid-Late Caledonian, forebulge in HercynianYanshanian and the latest compressional faulted block uplift in Mid-Late Himalayan. Meanwhile,the study also suggests that the formation, reconstruction and stabilization of the uplift were controlled by the development and evolution of fault systems clearly. In the early forebulge stage, it was mainly presented as flexural deformation without the developing of thrust faults in the Bachu area; to the late stage, under the influence of violent lateral compression deformation, the faulted block uplift formed finally.展开更多
A study of faults and their control of deep gas accumulations has been made on the basis of dividing fault systems in the Xujiaweizi area. The study indicates two sets of fault systems are developed vertically in the ...A study of faults and their control of deep gas accumulations has been made on the basis of dividing fault systems in the Xujiaweizi area. The study indicates two sets of fault systems are developed vertically in the Xujiaweizi area, including a lower fault system and an upper fault system. Formed in the period of the Huoshiling Formation to Yingcheng Formation, the lower fault system consists of five fault systems including Xuxi strike-slip extensional fault system, NE-trending extensional fault system, near-EW-trending regulating fault system, Xuzhong strike-slip fault system and Xudong strike-slip fault system. Formed in the period of Qingshankou Formation to Yaojia Formation, the upper fault system was affected mainly by the boundary conditions of the lower fault system, and thus plenty of muiti-directionally distributed dense fault zones were formed in the T2 reflection horizon. The Xuxi fault controlled the formation and distribution of Shahezi coal-measure source rocks, and Xuzhong and Xndong faults controlled the formation and distribution of volcanic reservoirs of Y1 Member and Y3 Member, respectively. In the forming period of the upper fault system, the Xuzhong fault was of successive strong activities and directly connected gas source rock reservoirs and volcanic reservoirs, so it is a strongly-charged direct gas source fault. The volcanic reservoir development zones of good physical properties that may be found near the Xuzhong fault are the favorable target zones for the next exploration of deep gas accumulations in Xujiaweizi area.展开更多
The Astara Fault System（AFS） is located in the northwest Alborz, east of Talesh Mountain（TM） and west of the South Caspian Basin（SCB）. The AFS is one of the basement rock faults in Iran that is heavily involved ...The Astara Fault System（AFS） is located in the northwest Alborz, east of Talesh Mountain（TM） and west of the South Caspian Basin（SCB）. The AFS is one of the basement rock faults in Iran that is heavily involved in seismotectonic activity of the Talesh region, and to which subsidence of the SCB is attributed. There is little information available concerning previous AFS seismic activities and its properties. In order to elucidate the seismic behavior and activities of the AFS, we conducted a research study on paleoseismology of the fault. Based on paleoseismic evidence, two scenarios could be taken into consideration, one of which has three and another has four seismic events with magnitudes Mw in the range of 6.7 to 7.2. Evidence of these seismic events is within sedimentary succession as they have occurred during the past 3 ka（this age is determined based on the deposition rate of the region）. Six carbon samples were taken for C^14 age determination tests, the results of which clearly demonstrated that the EvIV（scenario A） and EvⅢ（scenario B） had occurred before 27,444 cal BP, while other events occurred in the time period between 27,444 cal BP and 3 ka ago. If we consider the occurrence of three or four seismic events（based on the two scenarios） to be between 27,444 cal BP and 3 ka ago, the average recurrence interval is 7,119 ± 1,017, but evidence for these events has been removed. If we assume EvI to be the youngest event（in both scenarios）, the minimum elapsed time is therefore 3 ka.展开更多
The Kale-Yeşilyurt Fault Zone(KYFZ)exhibits recent tectonic reactivation,which is critical for understanding regional seismicity and the geodynamic evolution of the East Anatolian Fault System(EAFS).This study integra...The Kale-Yeşilyurt Fault Zone(KYFZ)exhibits recent tectonic reactivation,which is critical for understanding regional seismicity and the geodynamic evolution of the East Anatolian Fault System(EAFS).This study integrates kinematic and morphometric analyses to explore the reactivation processes along the fault.Kinematic analysis,incorporating fault-slip data and stress inversion,reveals complex deformation patterns characterized by strike-slip and extensional movements,with NE-SW trending minimum stress axes.February 6,2023,earthquake sequence highlighted significant stress accumulation along the Kale-Yeşilyurt and Göksun segments.Fieldwork and morphometric analyses,including mountain front sinuosity(Smf)and drainage basin analysis,suggest variable uplift rates and tectonic forces,with an asymmetric westward-directed uplift along the KYFZ.HI-HC index analysis underscores rapid uplift,particularly in the western basin,signaling ongoing tectonic and geomorphic activity.The normalized channel steepness index(Ksn)values reveal variations in erosion rates,providing insight into regional uplift patterns and knickpoint distribution.While morphometric indicators collectively point to high tectonic activity along the Yeşilyurt segment,the Kale segment exhibits particularly intense activity with a dominant normal fault component.The 2020 Sivrice earthquake and the 2023 earthquake doublet further emphasize the structural complexity of the fault system and underscore the KYFZ’s pivotal role in the active tectonics of the EAFS.Future research incorporating advanced geospatial technologies is vital for improving our understanding of tectonic processes,mitigating earthquake hazards,and enhancing seismic risk assessments.展开更多
From China to Russia,Tan-Lu fault system stretches for thousands of kilometers,towards NE 30°.The authors have collected more than ten magnetotelluric profile that China and Russia have carried out,in the studied...From China to Russia,Tan-Lu fault system stretches for thousands of kilometers,towards NE 30°.The authors have collected more than ten magnetotelluric profile that China and Russia have carried out,in the studied area of the Tan-Lu fault's northern section,and have analyzed electrical characteristics of the relevant profiles.Deriving the following conclusions:(1)Jiamusi-Bureya plots,etc.,demonstrate the high resistance of Kernel;(2)Fold belt attributed to the land showed high and low resistance stitching,associated with not only terrane accretion,but also upper mantle upwelling;below the sedimentary basin,the resistivity of the upper mantle is lower and closer to the surface comparing with the adjacent area(100-150);(3)In the system of Tan-Lu fracture,Yishu and Dunmi fracture,etc.are expressed as vertical low-resistivity zone;(4)There may exist subducted old-fashioned piece under Jiamusi and Bureya plots.展开更多
Due to its strategic location, the Astara fault system （AFS）, which is located in Iran, has given rise to a number of earthquakes. In spite of its frequent seismic events, limited information is available for AFS. S...Due to its strategic location, the Astara fault system （AFS）, which is located in Iran, has given rise to a number of earthquakes. In spite of its frequent seismic events, limited information is available for AFS. Slip rate is one of the important variables for future scrutiny of seismic risk of this fault system. The main objective of this research is to study slip rates at intermediate and short terms for this fault system using geological, geodetic observations and empirical method. Using the geological data, the intermediate-term horizontal and vertical slip rates for AFS have been determined to be 2.8±0.2 and 0.27±0.03 mm/year, respectively. In addition, the short-term slip rates of the fault, based on the geodetic method （using displacement values of two GPS stations： HASH and DAMO） and assuming attenuation of 60% （to fold the sediment of South Caspian Basin and shortening of Talesh Mountain range）, determined to be 1.23±0.03 and 2.05±0.05 mm/year for the horizontal and vertical slips, respectively. Finally, evaluation of the slip rate using empirical relationship yields 10 mm/year for the entire fault system, which seems rather implausible.展开更多
We have made careful field investigation and trench exploration to the Xishan fault system in west of Urumqi, and an integrated analysis in conjunction with data of deep seismic sounding. Our result suggests that unde...We have made careful field investigation and trench exploration to the Xishan fault system in west of Urumqi, and an integrated analysis in conjunction with data of deep seismic sounding. Our result suggests that under the SN-oriented compressive stress, the Xishan block moves steadily toward the Tianshan Mountains in south, resulting in southward thrust-slip and crustal shortening, particularly the southward thrust of the Xishan fault which serves as the main boundary in south. North of the Xishan fault are the Wangjiagou fault and Jiujiawan fault which are the secondary faults associated with the Xishan fault in generation. Both faults have slippage along horizons during the uplift of the Xishan block, and the Jiujiawan fault has also a component of normal faulting due to the influence of the Bogeda nappe structure. These two faults accommodate the fold deformation of the hanging wall of the Xishan fault, thus the Xishan fault-bounded swell is characterized by monocline. All secondary faults of the Xishan fault system constitute a common seismogenic structural system, so that their seismic hazards should be considered in an equal manner.展开更多
The purpose of this paper is to analyze the regional fault systems o f Qaidam basin and adjacent orogenic belts. Field investigation and seismic interp retation indicate that five regional fault systems occurred in t...The purpose of this paper is to analyze the regional fault systems o f Qaidam basin and adjacent orogenic belts. Field investigation and seismic interp retation indicate that five regional fault systems occurred in the Qaidam and ad jacent mountain belts, controlling the development and evolution of the Qaidam b asin. These fault systems are: (1)north Qaidam Qilian Mountain fault system; (2 ) south Qaidam East Kunlun Mountain fault system; (3)Altun strike slip fault s ystem; (4)Elashan strike slip fault system, and (5) Gansen Xiaochaidan fault s ystem. It is indicated that the fault systems controlled the orientation of the Qaidam basin, the formation and distribution of secondary faults within the basi n, the migration of depocenters and the distribution of hydrocarbon accumulation belt.展开更多
基金supported by funding from the NSFC(42030306 and 41672216)the National Key R&D Program of China(2016YFC0600102-03).
文摘The largest Tan-Lu active fault system in northeastern Asia,spans approximately 3500 km in length and varies in width from 10 km to 200 km.In 1668,an earthquake with a magnitude of 8.5 occurred in Tancheng,causing the loss of over 50000 lives.To constrain the timing and process of the Tan-Lu fault system on eastern Asian margin,this study presents the field mapping,thin section observation,geochronology,and microanalysis of Weiyuanpu-Yehe ductile shear zone(WYSZ)of the northern Tan-Lu fault system.Kinematic indicators and microstructures suggest a sense of sinistral strike-slip.The deformation temperature of the mylonite is mediate to high based on the quartz deformation,c-axis fabrics.The differential stress of the shear zone is 20‒40 MPa using quartz paleopiezometry.The dikes within the shear zone yielded zircon U-Pb ages of 165‒163 Ma.However,due to the ambiguous geological relationship between the dikes and shear zone,additional geochronology is warranted.Since the Mesozoic era,based on the exposure of mylonite and dikes,the upper crust has been extensively eroded,exposing the ductile shear zone.Moreover,the understanding of the geometry and process of pre-existing structures has fundamental implications for predicating the potential earthquakes for the Tan-Lu fault system.
基金supported by the National Key Research and Development Project of China(No.2021YFC3000600)。
文摘The Longmenshan structural belt on the eastern edge of the Tibetan Plateau experienced the impactful Mw7.92008 Wenchuan Earthquake,causing a 350 km surface rupture.Traditional models attribute this to the Beichuan and Pengguan faults,but our research reveals a complex fault system at the northern end,with inconsistencies in surface rupture,aftershock distribution,and focal mechanisms.We integrate shallow geology,active source seismic reflection,and magnetotelluric profiling to establish a deep structural model for the northern end of the Longmenshan structural belt.This area exhibits dominant reverse thrust nappe tectonics,and analyzing the tectonic evolution history provides insights into deformation propagation from the orogenic belt toward the Sichuan Basin.Focal mechanism analysis and relocated aftershock data reveals two distinct types of seismogenic structures in the northern end of the Longmenshan structural belt.In the middle to northern segments,the reverse fault type is attributed to reactivated pre-existing faults.Conversely,at the northern end,the strike-slip fault type originates from high-angle co-seismic rupture cutting through pre-existing reverse faults.This study enhances our understanding of fault complexity and seismic mechanisms in the northeastern Longmenshan structural belt,providing new insights into regional tectonics.
基金partially supported by the Fırat University Scientific Research Project in Elazığ,Türkiye,under Project Number ADEP.23.12.
文摘The Palu segment,situated in the northeastern part of the East Anatolian Fault System(EAFS),is a crucial structural feature with notable seismic potential.This study examines the paleoseismic activity of the Palu segment through trench excavations and geochronological analyses utilizing Optically Stimulated Luminescence(OSL)and radiocarbon(14C)dating methods.Two trenches,located near Karşıbahçeler,exposed evidence of multiple surface-rupturing seismic events spanning the Holocene and Pleistocene epochs.Chronological analyses identified five distinct seismic events in trench 1(P1),dated between 94.09±6.07 ka and 0.84±0.45 ka,and three events in trench 2(P2),dated between 28.83±1.61 ka and 351±21 BP.Bayesian analysis using Oxcal distribution suggested event timings between 90.52±25.99 ka and 1.25±0.55 ka.Comparative analysis with historical earthquake records correlates the most recent event with the 1789 or 1874 AD earthquakes,while the penultimate event matches the 995 AD earthquake.Earlier events reflect prehistoric tectonic activity.The recurrence intervals for these events range from 710 to 5,370 years during the Holocene,with evidence of seismic activity extending into the Pleistocene.Stress inversion analyses and geodetic data indicate a predominantly strike-slip stress regime,consistent with geometry of the fault.These findings provide critical insights into the long-term seismic behavior and recurrence patterns of the Palu segment,enhancing seismic hazard assessments for the region.
基金supported by the Open Funds for Hubei Key Laboratory of Marine Geological Resources,China University of Geosciences(No.MGR202303)the National Natural Science Foundation of China(No.41672110)。
文摘The Songliao Basin in northeast China is one of the largest petroliferous basins worldwide,and features the T_(2)fault system,which consists of numerous minor extensional normal faults.This study combines high-resolution 3D seismic datasets to detail the characteristics of the T_(2)fault system,contributing two key findings:(1)The T_(2)faults are confirmed as polygonal fault systems,characterized by closely spaced,layer-bounded faults with small throws,high dip angles,and random orientations,forming intricate polygonal networks.(2)The study reveals the influence of tectonic stresses on the fault system,showing spatial variations across different tectonic units.In depressions,T_(2)faults exhibit short lengths,small throws,high density,and multiple directions.In contrast,in inverted anticline belts,they have longer lengths,bigger throws,higher density,and concordant orientations.These variations demonstrate the impact of tectonic inversion on the development of T_(2)faults.The significance of this research lies in presenting a typical polygonal fault system developed in a deep lake succession and was superposed the influence by regional tectonic stress coeval with its development.The new insights facilitate a reevaluation of the T_(2)fault system's role in hydrocarbon migration and accumulation within the Songliao Basin.
基金supported mainly by the National Key Basic Research Program(No.2004CB418401)the National Natural Science Foundation of China(grant No.40472109)+1 种基金partly from the Joint Earthquake Science Foundation of China(grant No.105066)the SASAKAWA Scientific Grant from the Japan Science Society.
文摘Recent studies on the Xianshuihe-Xiaojiang fault system suggest that the Late Quaternary strike-slip rate is approximately uniform along the entire length of the fault zone, about 15±2 mm/a. This approximately uniform strike slip rate strongly supports the clockwise rotation model of the southeastern Tibetan crust. By approximating the geometry of the arc-shaped Xianshuihe-Xiaojiang fault system as a portion of a small circle on a spherical Earth, the 15±2 mm/a strike slip rate corresponds to clockwise rotation of the Southeastern Tibetan Block at the （5.2±0.7）×10^-7 deg/a angular velocity around the pole （21°N, 88°E） relative to the Northeast Tibetan Block. The approximately uniform strike slip rate along the Xianshuihe-Xiaojiang fault system also implies that the Longmeushan thrust zone is not active, or at least its activity has been very weak since the Late Quaternary. Moreover, the total offset along the Xiaushuihe-Xiaojiang fault system suggests that the lateral extrusion of the Southeastern Tibetan Block relative to Northeastern Tibetan Block is about 160 km and 200-240 km relative to the Tarim-North China block. This amount of lateral extrusion of the Tibetan crust should have accommodated about 13-24% convergence between India and Eurasia based on mass balance calculations. Assuming that the slip rate of 15±2 mm/a is constant throughout the entire history of the Xianshuihe-Xiaojiang fault system, 11±1.5 Ma is needed for the Xianshuihe-Xiaojiang fault system to attain the 160 km of total offset. This implies that left-slip faulting on the Xianshuihe-Xiaojiang fault system might start at 11±1.5 Ma.
文摘The fault system of Liaodong Bay developed extensively under the control of the Tanlu Fault. The fault system can be grouped into strike-slip faults of grade Ⅰ, trunk faults of grade Ⅱand branch faults （induced faults） of grade Ⅲ respectively based on its developmental scale. The faults of grade Ⅰ and Ⅱwere deep, early and large while the faults of grade Ⅲwere shallow, late and small. The formation, evolution and distribution features played a significant role in controlling the migration of oil and gas in both horizontal and vertical directions. The fluid transfer in the fault system occurred in the process of faulting. The strike-slip and trunk faults moved actively forming predominant pathways for oil and gas migration. The branch faults, with weak activity, generally controlled the development of traps and were beneficial for the accumulation and preservation of oil and gas. The faults of grade Ⅰ and Ⅱ formed the major migration pathways for oil and gas, but their fault activity rates appeared to vary along their strikes. The zones with a relatively low fault activity rate might be favorable for oil and gas accumulation. When the activities of strike-slip, trunk, and branch faults came to a halt, the fault seal behavior had a vitally important effect on the accumulation of oil and gas. The controlling role of the fault over fluid distribution was further analyzed by calculating the fault activity quantitatively.
基金sponsored by the National Natural Science Foundation of China(Nos.41172125,40972090)the National Basic Research Program of China(Nos.2012CB214804,2005CB422107)+2 种基金the Investigation and Evaluation on Strategic Region of National Oil and Gas Resource(No.2009GYXQ02-05)the Doctoral Fund of Ministry of Education of China(No.200804250001)the National Key Scientific Project of China(No.2011ZX05002-003-001HZ)
文摘This article aims to analyze the main controlling factors of development, distribution and evolution of the fault systems in the Tarim Basin. Based on the seismic profile interpretation, compre- hensive analysis of the drilling and geologic data, six fault systems maybe recognized in the Tarim Basin, they are the foreland fault system of the South Tianshan Mountain, the northern Tarim uplift fault sys- tem, North Tarim depression fault system, central fault system, Southwest Tarim fault system, and Southeast Tarim fault system. It is indicated that the main differences exist at the development, evolu- tion and distribution of the fault systems in the Tarim Basin. The sub-fault systems can be recognized according to the differences of the fault development and distribution in the interior of the fault system. It is characterized that the multi-level differential development and distribution of the fault systems ex- ist in the Tarim Basin. The fault belt developed in the Paleozoic strata mainly distribute at the pa- leo-uplift and paleo-slope in the interior of the Tarim Basin, and the fault belt occurred in the Meso-Cenozoic beds mainly develop at the peripheral foreland depressions. Zonal and segment differ- ential development and distribution of the fault systems also exist in the Tarim Basin. The formation and distribution of the Tarim fault systems is of complex controlling mechanisms. Poly-phase structural movement and tectonic transition controls the multi-phase differential development and distribution of the fault systems in the Tarim Basin. Multi-level differential development and distribution is controlled by multi-level detachment belt and regional unconformities. Zonal and segment differential develop- ment and distribution of the Tarim fault systems maybe controlled by pre-existed basement structural texture. The major direction of the fault systems in the Tarim Basin is controlled by the later stage basin-mountain coupling.
基金supported by the Science Project awarded to A. Lin from the Ministry of Education of China (No. 23253002)the Culture, Sports, Science, and Technology of Japan, and China Postdoctoral Science Foundation (No. 2016M591817) to Bing Yan
文摘Coulomb stress accumulation and releasing history and its relationship with the occur- rence of strong historical earthquakes could deepen our understanding of the occurrence pattern of strong earthquakes and hence its seismic potential in future. The sinistral strike-slip Xianshuihe- Xiaojiang fault zone （XXFS） is one of the most dangerous fault zones in China, extending 1 500-km- long from the central Tibetan Plateau to the Red River fault zone. There are 35 M≥6.5 historical earth- quakes occurred since 1327, hence it is an ideal site for studying the Coulomb stress evolution history and its relationship with the occurrences of strong earthquakes. In this study, we evaluated the Cou- lomb stress change history along the XXFS by synthesizing fault geometry, GPS data and historical earthquakes. Coulomb stress change history also revealed different patterns of historical earthquakes on different segments of the XXFS, such as characteristic recurrence intervals along the Salaha-Moxi fault and super-cycles along the Xianshuihe fault. Based on the occurrence pattern of past historical earthquakes and current Coulomb stress field obtained in this study, we suggest positive ACFS and hence high seismic potential along the Salaha-Moxi fault and the Anninghe fault.
文摘The Bodong Sag,located in the Bohai Sea,offshore China,is one of the most petroliferous basins in China.Based on three dimensional seismic reflection data and time slice data,we analyze the fault system of the Bodong area in detail,establish the fault structure pattern of different types and summarize the distribution of the fault system.It is concluded that the development characteristics of the Cenozoic fault system are in accordance with the dextral stress field of the Tanlu Fault,which displayed a brush structure with NNE strike-slip faults as its principal faults,NE-trending extensional faults as secondary faults and EW-trending faults as minor faults.Faults can be divided into （1） strike-slip type,（2） extensional type,（3） strike-slip extensional type and （4） extensional strike-slip type.The spatial structures of different faults have obvious differences because of the fault properties and activity intensity.The fault system at different stages shows tremendous differences because of the transition of the Tanlu Fault from sinistral strike-slip to dextral strike-slip,the transition between extension and strike-slip,and the transition from mantle upwelling to thermal subsidence.According to the controlling effect of faults on basin structure,the Cenozoic basin experienced four evolutionary stages,（a） transition stage from sinistral strike-slip to dextral strike-slip,（b） strike-slip extensional faulted stage,（c） extensional strike-slip faulted stage and （d） strike-slip depression stage.The identification of temporal and spatial differences of faults could be used as a significant guideline for oil and gas exploration in the Bodong area.
基金supported by the National Natural Sciences Foundation of China(Grants No.41202156 and 41330211)China Geological Survey(Grants No.12120115026901 and 12120115027001)the Institute of Geology,CAGS(Grant No.J1520)
文摘As one of the longest strike-slip fault in Asia,the Altyn Tagh Fault（ATF）defines the northern boundary of the Tibetan Plateau and plays a significant role inaccommodating the deformation resulting from the IndiaAsia convergence.
基金the financial support from National Natural Science Foundation of China(51504268)National Technology Major Project of China(2016ZX05014).
文摘Gas injection serves as a main enhanced oil recovery(EOR)method in fractured-vuggy carbonate reservoir,but its effect differs among single wells and multi-well groups because of the diverse fractured-vuggy configuration.Many researchers conducted experiments for the observation of fluid flow and the evaluation of production performance,while most of their physical models were fabricated based on the probability distribution of fractures and caves in the reservoir.In this study,a two-dimensional physical model of the karst fault system was designed and fabricated based on the geological model of TK748 well group in the seventh block of the Tahe Oilfield.The fluid flow and production performance of primary gas flooding were discussed.Gas-assisted gravity flooding was firstly introduced to take full use of gas-oil gravity difference,and its feasibility in the karst fault system was examined.Experimental results showed that primary gas flooding created more flow paths and achieved a remarkable increment of oil recovery compared to water flooding.Gas injection at a lower location was recommended to delay gas breakthrough.Gas-assisted gravity flooding achieved more stable gas-displacing-oil because oil production was at a lower location,and thus,the oil recovery was further enhanced.
文摘The Kangding City in eastern Tibet is at high risk due to frequent strong earthquakes along the Xianshuihe sinistral strike-slip fault bounding the Chuandian Block to the northeast.The knowledge of paleo-seismicity recurrence along this fault system is key to the evaluation of earthquake hazards in this region;thus,more accurate paleoseismic information are required.We examined the paleo-seismicity along the Zheduotang fault in the central segment of the Xianshuihe fault system by applying the field investigation,trenching,and Quaternary dating methods(e.g.,OSL and^(14)C).Field observations found~8.5 m offset of stream by sinistral slip along the Zheduotang fault.We trenched the central fault zone of the Zheduotang fault and found that the colluvial wedges and five buried,discontinuous,A-soil horizons progressively have been offset in the shallow graben on the SW-side of the main fault indicative of the paleo-earthquakes.The dating results of OSL and^(14)C,in line with existing data,enable us to establish the paleo-seismic history of the Zheduotang fault.It shows at least eight surface ruptures in the last 7500 years identified from displaced buried soils,colluvial wedges and terraces.Our study reveals~100 years minimum paleo-earthquake recurrence,suggesting potential large earthquakes in the Kangding area in the future.
基金supported by the National Science and Technology Major Project (No. 2011ZX05009-001)the National Natural Science Foundation of China (No. 41102071)
文摘The Bachu （巴楚） uplift is one of the most active tectonic regions nowadays in the Tarim basin, which is also a faulted block uplift that was intensively active during the Cenozoic. This study was based primarily on the geological structure interpretation of seismic profiles, applying the theories and methods of basin dynamics, structural analysis and tectono-stratigraphic analysis, the geometry and kinematics features of the fault systems in the Bachn uplift were analyzed in detail. Our study shows that each fault belt is mainly characterized by compression and overthrusting, most of the faults initiated and activated during the Mid-Late Himalayan period, and that the general structural styles of the Bachu uplift were basement-involved pop-up thrust faulted block uplift, of which the southern margin was covered by the large-scale decollement fault system. The basement-involved structures widely developed in the higher position of the basement uplift, while decollement fault system developed mainly at the position with gypsum mudstone. The evolution process of Bachu uplift included back-bulge slope of the peripheral foreland basin in Mid-Late Caledonian, forebulge in HercynianYanshanian and the latest compressional faulted block uplift in Mid-Late Himalayan. Meanwhile,the study also suggests that the formation, reconstruction and stabilization of the uplift were controlled by the development and evolution of fault systems clearly. In the early forebulge stage, it was mainly presented as flexural deformation without the developing of thrust faults in the Bachu area; to the late stage, under the influence of violent lateral compression deformation, the faulted block uplift formed finally.
基金supported by the National Natural Foundation Project Polygonal Fault Genetic Mechanism and its Reservoir Controlling Mechanism in Rift Basin (number: 41072163) financial aid
文摘A study of faults and their control of deep gas accumulations has been made on the basis of dividing fault systems in the Xujiaweizi area. The study indicates two sets of fault systems are developed vertically in the Xujiaweizi area, including a lower fault system and an upper fault system. Formed in the period of the Huoshiling Formation to Yingcheng Formation, the lower fault system consists of five fault systems including Xuxi strike-slip extensional fault system, NE-trending extensional fault system, near-EW-trending regulating fault system, Xuzhong strike-slip fault system and Xudong strike-slip fault system. Formed in the period of Qingshankou Formation to Yaojia Formation, the upper fault system was affected mainly by the boundary conditions of the lower fault system, and thus plenty of muiti-directionally distributed dense fault zones were formed in the T2 reflection horizon. The Xuxi fault controlled the formation and distribution of Shahezi coal-measure source rocks, and Xuzhong and Xndong faults controlled the formation and distribution of volcanic reservoirs of Y1 Member and Y3 Member, respectively. In the forming period of the upper fault system, the Xuzhong fault was of successive strong activities and directly connected gas source rock reservoirs and volcanic reservoirs, so it is a strongly-charged direct gas source fault. The volcanic reservoir development zones of good physical properties that may be found near the Xuzhong fault are the favorable target zones for the next exploration of deep gas accumulations in Xujiaweizi area.
文摘The Astara Fault System（AFS） is located in the northwest Alborz, east of Talesh Mountain（TM） and west of the South Caspian Basin（SCB）. The AFS is one of the basement rock faults in Iran that is heavily involved in seismotectonic activity of the Talesh region, and to which subsidence of the SCB is attributed. There is little information available concerning previous AFS seismic activities and its properties. In order to elucidate the seismic behavior and activities of the AFS, we conducted a research study on paleoseismology of the fault. Based on paleoseismic evidence, two scenarios could be taken into consideration, one of which has three and another has four seismic events with magnitudes Mw in the range of 6.7 to 7.2. Evidence of these seismic events is within sedimentary succession as they have occurred during the past 3 ka（this age is determined based on the deposition rate of the region）. Six carbon samples were taken for C^14 age determination tests, the results of which clearly demonstrated that the EvIV（scenario A） and EvⅢ（scenario B） had occurred before 27,444 cal BP, while other events occurred in the time period between 27,444 cal BP and 3 ka ago. If we consider the occurrence of three or four seismic events（based on the two scenarios） to be between 27,444 cal BP and 3 ka ago, the average recurrence interval is 7,119 ± 1,017, but evidence for these events has been removed. If we assume EvI to be the youngest event（in both scenarios）, the minimum elapsed time is therefore 3 ka.
文摘The Kale-Yeşilyurt Fault Zone(KYFZ)exhibits recent tectonic reactivation,which is critical for understanding regional seismicity and the geodynamic evolution of the East Anatolian Fault System(EAFS).This study integrates kinematic and morphometric analyses to explore the reactivation processes along the fault.Kinematic analysis,incorporating fault-slip data and stress inversion,reveals complex deformation patterns characterized by strike-slip and extensional movements,with NE-SW trending minimum stress axes.February 6,2023,earthquake sequence highlighted significant stress accumulation along the Kale-Yeşilyurt and Göksun segments.Fieldwork and morphometric analyses,including mountain front sinuosity(Smf)and drainage basin analysis,suggest variable uplift rates and tectonic forces,with an asymmetric westward-directed uplift along the KYFZ.HI-HC index analysis underscores rapid uplift,particularly in the western basin,signaling ongoing tectonic and geomorphic activity.The normalized channel steepness index(Ksn)values reveal variations in erosion rates,providing insight into regional uplift patterns and knickpoint distribution.While morphometric indicators collectively point to high tectonic activity along the Yeşilyurt segment,the Kale segment exhibits particularly intense activity with a dominant normal fault component.The 2020 Sivrice earthquake and the 2023 earthquake doublet further emphasize the structural complexity of the fault system and underscore the KYFZ’s pivotal role in the active tectonics of the EAFS.Future research incorporating advanced geospatial technologies is vital for improving our understanding of tectonic processes,mitigating earthquake hazards,and enhancing seismic risk assessments.
基金the Project 12-05-91158 of the National Natural Science Foundation of China(NSFC)the Russian Academy of Sciences"Deep structure,evolution of the sedimentogenesis and tectonics of Northeastern China and southeastern Far East Russia"
文摘From China to Russia,Tan-Lu fault system stretches for thousands of kilometers,towards NE 30°.The authors have collected more than ten magnetotelluric profile that China and Russia have carried out,in the studied area of the Tan-Lu fault's northern section,and have analyzed electrical characteristics of the relevant profiles.Deriving the following conclusions:(1)Jiamusi-Bureya plots,etc.,demonstrate the high resistance of Kernel;(2)Fold belt attributed to the land showed high and low resistance stitching,associated with not only terrane accretion,but also upper mantle upwelling;below the sedimentary basin,the resistivity of the upper mantle is lower and closer to the surface comparing with the adjacent area(100-150);(3)In the system of Tan-Lu fracture,Yishu and Dunmi fracture,etc.are expressed as vertical low-resistivity zone;(4)There may exist subducted old-fashioned piece under Jiamusi and Bureya plots.
文摘Due to its strategic location, the Astara fault system （AFS）, which is located in Iran, has given rise to a number of earthquakes. In spite of its frequent seismic events, limited information is available for AFS. Slip rate is one of the important variables for future scrutiny of seismic risk of this fault system. The main objective of this research is to study slip rates at intermediate and short terms for this fault system using geological, geodetic observations and empirical method. Using the geological data, the intermediate-term horizontal and vertical slip rates for AFS have been determined to be 2.8±0.2 and 0.27±0.03 mm/year, respectively. In addition, the short-term slip rates of the fault, based on the geodetic method （using displacement values of two GPS stations： HASH and DAMO） and assuming attenuation of 60% （to fold the sediment of South Caspian Basin and shortening of Talesh Mountain range）, determined to be 1.23±0.03 and 2.05±0.05 mm/year for the horizontal and vertical slips, respectively. Finally, evaluation of the slip rate using empirical relationship yields 10 mm/year for the entire fault system, which seems rather implausible.
基金supported by Active Fault Detection and Earthquake Risk Estimation of Urumqi (1-4-31)Sub-topic of National Science and Technology Support Project (2006BAC13B010102)International Cooperation Key Project of Ministry of Science and Technology "Research on New Methods of Earthquake Prediction and Risk Estimation"(2004BFBA0005)
文摘We have made careful field investigation and trench exploration to the Xishan fault system in west of Urumqi, and an integrated analysis in conjunction with data of deep seismic sounding. Our result suggests that under the SN-oriented compressive stress, the Xishan block moves steadily toward the Tianshan Mountains in south, resulting in southward thrust-slip and crustal shortening, particularly the southward thrust of the Xishan fault which serves as the main boundary in south. North of the Xishan fault are the Wangjiagou fault and Jiujiawan fault which are the secondary faults associated with the Xishan fault in generation. Both faults have slippage along horizons during the uplift of the Xishan block, and the Jiujiawan fault has also a component of normal faulting due to the influence of the Bogeda nappe structure. These two faults accommodate the fold deformation of the hanging wall of the Xishan fault, thus the Xishan fault-bounded swell is characterized by monocline. All secondary faults of the Xishan fault system constitute a common seismogenic structural system, so that their seismic hazards should be considered in an equal manner.
文摘The purpose of this paper is to analyze the regional fault systems o f Qaidam basin and adjacent orogenic belts. Field investigation and seismic interp retation indicate that five regional fault systems occurred in the Qaidam and ad jacent mountain belts, controlling the development and evolution of the Qaidam b asin. These fault systems are: (1)north Qaidam Qilian Mountain fault system; (2 ) south Qaidam East Kunlun Mountain fault system; (3)Altun strike slip fault s ystem; (4)Elashan strike slip fault system, and (5) Gansen Xiaochaidan fault s ystem. It is indicated that the fault systems controlled the orientation of the Qaidam basin, the formation and distribution of secondary faults within the basi n, the migration of depocenters and the distribution of hydrocarbon accumulation belt.
