Although the late Quaternary slip rate of the Northern Margin Fault of the Huaizhuo Basin(NFHB)was studied approximately 30 years ago using thermoluminescence and geomorphic methods,the underlying uncertainty cannot b...Although the late Quaternary slip rate of the Northern Margin Fault of the Huaizhuo Basin(NFHB)was studied approximately 30 years ago using thermoluminescence and geomorphic methods,the underlying uncertainty cannot be neglected,considering the limitations resulting from age and displacement measurements.Accordingly,we attempted to re-estimate the late Quaternary slip rate of the NFHB using high-precision remote sensing image interpretation,large-scale geological and geomorphic mapping,paleoseismic analysis,and Quaternary geochronology testing.The results,based on stratigraphic dislocation and age constraint in the trenches,show that the present deformation of the NFHB has been dominated by the extension,with a vertical slip rate~0.04-0.11 mm/a.We estimate a vertical slip rate of~0.06 mm/a,with an R^(2) value of~0.91,which is much lower than the~0.5 mm/a result estimated previously.There are three possible reasons for this discrepancy.The first is the limitation resulting from dating and displacement measurements in earlier studies;the second is the slip decomposition caused by multiple branches of the NFHB,which leads to the low slip rate observed at a single fault;and third possible explanation is that the fault may be locked at present with a low slip rate,which means that the earthquake hazard of the NFHB cannot be ignored,and more in-depth research,such as geodetic and intensive observations of earthquake precursors,is urgently needed.This discovery poses a new challenge for the active study of the NFHB and the northeast corner of the Ordos Plateau in the North China Block.展开更多
We present in this paper some new evidence for the change during the Quaternary in kinematics of faults cutting the eastern margin of the Tibetan Plateau. It shows that significant shortening deformation occurred duri...We present in this paper some new evidence for the change during the Quaternary in kinematics of faults cutting the eastern margin of the Tibetan Plateau. It shows that significant shortening deformation occurred during the Early Pleistocene, evidenced by eastward thrusting of Mesozoic carbonates on the Pliocene lacustrine deposits along the Minjiang upstream fault zone and by development of the transpressional ridges of basement rocks along the Anninghe river valley. The Middle Pleistocene seems to be a relaxant stage with local development of the intra-mountain basins particularly prominent along the Minjiang Upstream and along the southern segment of the Anninghe River Valley. This relaxation may have been duo to a local collapse of the thickened crust attained during the late Neogene to early Pleistocene across this marginal zone. Fault kinematics has been changed since the late Pleistocene, and was predominated by reverse sinistral strike-slip along the Minshan Uplift, reverse dextral strike-slip on the Longmenshan fault zone and pure sinistral strike-slip on the Anninghe fault. This change in fault kinematics during the Quaternary allows a better understanding of the mechanism by which the marginal ranges of the plateau has been built through episodic activities.展开更多
Objective The lateral extrusion eastward of the Tibetan Plateau leads to the formation of the Sichuan–Yunnan block, which is the most representative active block in the southeastern margin of the Tibetan Plateau, cha...Objective The lateral extrusion eastward of the Tibetan Plateau leads to the formation of the Sichuan–Yunnan block, which is the most representative active block in the southeastern margin of the Tibetan Plateau, characterized by strong and frequent seismicity(Li Ping et al., 1975; Zhang Peizhen et al., 2003; Li Yong et al., 2017). Its eastern boundary is composed of sinistral faults including the Xianshuihe, Xiaojiang faults, etc., and the western展开更多
Based on the Chinese mainland GPS network (1994~1996), Fujian GPS network (1995~1997), cross fault deformation network (1982-1998), precise leveling network (1973~1980) and focal mechanism solutions of the recent sev...Based on the Chinese mainland GPS network (1994~1996), Fujian GPS network (1995~1997), cross fault deformation network (1982-1998), precise leveling network (1973~1980) and focal mechanism solutions of the recent several tens years, we synthetically and quantitatively studied the present-time crustal motion of the southeast coast of Chinese mainland-Fujian and its marginal sea. We find that this area with its mainland together moves toward SE with a rather constant velocity of 11 .2±3.0 mm/a. At the same time, there is a motion from the Quanzhou bay pointing to hinterland, with a major orientation of NW, extending toward two sides, and with an average velocity of 3.0±2.6 mm/a. The faults orienting NE show compressing motions, and the ones orienting NW show extending motions. The present-time strain field derived from crustal deformation is consistent with seismic stress field derived from the focal mechanism solutions and the tectonic stress field derived from geology data. The principal stress of compression orients NW (NWW) - SE (SEE). Demarcated by the NW orienting faults of the Quanzhou bay and Jinjiang-Yongan, the crustal motions show regional characteristics f the southwest of Fujian and the boundary of Fujian and Guangdong are areas of rising, the northeast of Fujian are areas of sinking. The horizontal strain rate and the fault motion of the former are both greater than the later. The side-transferring motion of Hymalaya collision zone and the compression of the west pacific subduction zone affect the motion of the research area. The amount of motion affected by the former is larger than the later, but the former is homogeneous and the later is not, which indicates that the events of strong earthquakes in this region relate more directly with western pacific subduction zone.展开更多
This study emphasizes the advantage of tectonic phase separation in determination of a tectonic evolution of complicated fault zones. The research focused on the Sudetic Marginal Fault Zone(SMFZ) –a 250 km long activ...This study emphasizes the advantage of tectonic phase separation in determination of a tectonic evolution of complicated fault zones. The research focused on the Sudetic Marginal Fault Zone(SMFZ) –a 250 km long active fault zone with documented intraplate seismicity situated on the NE margin of the Bohemian Massif(the Czech Republic). The tectonic history of the SMFZ as well as its kinematic development has been rather complicated and not quite understood. A field structural investigation was carried out in extensive surroundings of the fault zone. The fault-slip data were collected in a number of natural outcrops and quarries with the aim at establishing a robust and field-constrained model for local brittle structural evolution of the studied area. A paleostress analysis was calculated using the collected fault-slip data inversion. The T-Tecto software was utilized for semiautomatic separation of the paleostress phases. Simultaneously three methods of data separation were employed:(1) the Gauss inverse method,(2) the Visualization of Gauss object Function, and(3) the frequency analysis. Within the fault zone multiphase movements were observed on various types of faults as well as wide range of the kinematic indicators orientations. The frequency analysis confirmed the multiphase history of the SMFZ. The calculated tectonic phases were divided according to their relative age as constrained by cross cutting relationships and, where observed, multiple striations on a single fault plane and classified from the oldest to the younger. Data separation and inversion usingT-Tecto software with the Gauss inverse method revealed four different stress phases which are 3 strike-slip stress regimes and one compressional regime. The strike-slip regimes are characterized by σ1 trending NW-SE(43), NNE-SSW(18), ENE-WSW(76) and the compressional one by σ1 trending W-E(26). First, compression occurred parallel to the SMFZ supposedly during the Variscan period. Second, compression at an angle of 60° to general direction of the SMFZ yielded right-lateral movement along the fault zone. This is considered to have occurred during the late-Variscan and post-Variscan period. Third, compression in the W-E direction with almost vertical extension led to reverse movement along the fault zone. This is considered to have occurred during Cenozoic. Fourth, compression almost perpendicular to the SMFZ led to left-lateral transpression along the SMFZ. This is considered to have occurred during Quaternary.展开更多
Fault deformation characteristics in the northern margin of the Tibetan Plateau before the Menyuan Ms6.4 earthquake are investigated through time-series and structural geological analysis based on cross-fault observat...Fault deformation characteristics in the northern margin of the Tibetan Plateau before the Menyuan Ms6.4 earthquake are investigated through time-series and structural geological analysis based on cross-fault observation data from the Qilian Mountain-Haiyuan Fault belt and the West Qinling Fault belt. The results indicate： 1） Group short-term abnormal variations appeared in the Qilian Mountain-Haiyuan Fault belt and the West Qinling Fault belt before the Menyuan Ms6.4 earthquake. 2） More medium and short-term anomalies appear in the middle-eastern segment of the Qilian Mountain Fault belt and the West Qinling Fault belt, suggesting that the faults＇ activities are strong in these areas. The faults＇ activities in the middle-eastern segment of the Qilian Fault belt result from extensional stress, as before the earthquake, whereas those in the West Qinling Fault belt are mainly compressional. 3） In recent years, moderate-strong earthquakes occurred in both the Kunlun Mountain and the Qilian Mountain Fault belts, and some energy was released. It is possible that the seismicity moved eastward under this regime. Therefore, we should pay attention to the West Qinling Mountain area where an Ms6-7 earthquake could occur in future.展开更多
The formation of strath and strath terrace is closely related to tectonic uplift in the drainage basin. Based on the investigation of straths at Yandantu and Changcaogou on the eastern segment of the northern margin f...The formation of strath and strath terrace is closely related to tectonic uplift in the drainage basin. Based on the investigation of straths at Yandantu and Changcaogou on the eastern segment of the northern margin fault of Altun, and in combination with the paleoclimatic data, the tectonic uplift since late Epipleistocene as revealed by stream terraces at the two places is discussed. At Yandantu, three levels of stream terraces(T 1, T 2 and T 3)have developed since 16ka BP, where T 1, T 3 and T 2 are fill terraces and the buried major straths are exposed. The ages of three treads are dated to be about 16.1ka BP, 12.8ka BP and 6.2ka BP, respectively. The three terraces reflect three tectonic uplift events, while the ages of the treads represent the occurrence time of these events. The stream is still beveling the bedrock and widening the channel at present, and the modern strath is being generated. The uplift rate is 4.8～4.5mm/a since 16.1 ka BP in this area. From 12.8ka B.P to 6.2ka BP, The uplift rate was 6.4mm/a. The uplift rate is 3.1mm/a since 6.2ka BP. At Changcaogou, four levels of stream terraces(T 1, T 2, T 3 and T 1′)have developed since 7ka BP. All of them are fill terraces. There are buried straths under the deposits. The buried major strath is exposed on T 3 and T 2 and the minor strath on T 1′and T 1. The ages of treads of the three terraces (T 3, T 2 and T 1′) are 7 ka BP, 3 ka BP and 2.5 ka BP, respectively. The four terraces reflect two uplift events induced by tectonic activities. One occurred in about 7 ka BP, and the other in 3ka BP. The uplift rate is 5.9mm/a since 7.0 ka BP at Changcaogou. From 7ka BP to 3ka BP, the uplift rate was 7.0mm/a, and since 3ka BP till now, the uplift rate is 4.7 mm/a.展开更多
The Yuguang basin is a half-graben basin in the basin-range tectonic zone in northwest Beijing,located at the northern end of the Shanxi graben system,and the Yuguang basin southern marginal fault( YBSMF) controls the...The Yuguang basin is a half-graben basin in the basin-range tectonic zone in northwest Beijing,located at the northern end of the Shanxi graben system,and the Yuguang basin southern marginal fault( YBSMF) controls the formation of this basin. A linear fault escarpment has formed in the proluvial fan on the piedmont fault zone of the Tangshankou segment of YBSMF. A trench across this escarpment reveals three paleo-earthquake events on two active faults. One fault ruptured at about 9 ka for the first time,and then faulted again at about 7. 3 ka,causing the formation and synchronous activity of another fault.Finally,they faulted for the third time,but we cannot determine the faulting time due to the lack of relevant surface deposition. The accumulative vertical displacement of these three events is about 8. 1 m. We estimate that the average recurrence period of the piedmont fault is about 1. 7 ka,and the average slip rate of the piedmont fault is about1. 6 mm/a. We also estimate the reference magnitude of each event according to the empirical formula.展开更多
The geology and tectonics in the eastern margin of Tibetan Plateau are complex. The main tectonic framework is composed of blocks and faults. Using discontinuous global positioning system survey data for 2008–2014, t...The geology and tectonics in the eastern margin of Tibetan Plateau are complex. The main tectonic framework is composed of blocks and faults. Using discontinuous global positioning system survey data for 2008–2014, the velocity field for the Eurasia reference framework was obtained. Based on the velocity field, the present-day velocities of the blocks and boundary faults were estimated. The results reveal that the movement rates of the Chuan-Qing, South China, Chuan-Dian and Indo-China blocks are（17.02±0.60） mm/a,（8.77±1.51） mm/a,（13.85±1.31） mm/a and（6.84 ± 0.74） mm/a, respectively, and their movement directions are 99.5°, 120.3°, 142.9° and 153.3°, respectively. All blocks exhibit clockwise rotation. The displacement rates of the Xianshuihe, Longmenshan, Anninghe, Zemuhe, Xiaojiang and Red River faults are（7.30±1.25–8.30±1.26） mm/a,（10.07±0.97–11.79±0.89） mm/a,（0.96±0.74–2.98±1.73） mm/a,（2.03±0.49–3.20±0.73） mm/a,（3.45±0.40–6.02±0.50） mm/a and（6.23±0.56） mm/a, respectively. The Xianshuihe, Anninghe, Zemuhe and Xiaojiang faults show leftlateral strike-slip movement, while the Longmenshan and Red River faults show right-lateral strikeslip. These characteristics of the blocks and faults are related to the particular tectonic location and dynamic mechanism.展开更多
The western fault zone of the South China Sea is a strike-slip fault system and consists of four typical strike-slip faults. It is the western border of the South China Sea. The formation of the system is due to the e...The western fault zone of the South China Sea is a strike-slip fault system and consists of four typical strike-slip faults. It is the western border of the South China Sea. The formation of the system is due to the extrusion of Indo - China Peninsula caused by the collision of India with Tibet and the spreading of the South China Sea in Cenozoic. There are five episodes of tectonic movement along this fault zone, which plays an important role in the Cenozoic evolution of the South China Sea. By the physical modeling experiments, it can be seen the strike-slip fault undergoes the sinistral and dextral movement due to the relative movement velocity change between the South China Sea block and the Indo - China block. The fault zone controls the evolution of the pull basins locating in the west of the South China Sea.展开更多
The relationships between crustal stretching and thinning,basin structure and petroleum geology in Baiyun deep-water area were analyzed using large area 3D seismic,gravity,magnetic,ocean bottom seismic(OBS),deep-water...The relationships between crustal stretching and thinning,basin structure and petroleum geology in Baiyun deep-water area were analyzed using large area 3D seismic,gravity,magnetic,ocean bottom seismic(OBS),deep-water exploration wells and integrated ocean drilling program(IODP).During the early syn-rifting period,deep-water area was a half-graben controlled by high angle faults influenced by the brittle extension of upper crust.In the mid syn-rifting period,this area was a broad-deep fault depression controlled by detachment faults undergone brittle-ductile deformation and differentiated extension in the crust.In the late syn-rifting period,this area experienced fault-sag transition due to saucer-shaped rheology change dominated by crustal ductile deformation.A broad-deep fault depression controlled by the large detachment faults penetrating through the crust is an important feature of deep-water basin.The study suggests that the broad-deep Baiyun sag provides great accommodation space for the development of massive deltaic-lacustrine deposition system and hydrocarbon source rocks.The differentiated lithospheric thinning also resulted in the different thermal subsidence during post-rifting period,and then controlled the development of continental shelf break and deep-water reservoir sedimentary environment.The high heat flow background caused by the strong thinning of lithosphere and the rise of mantle source resulted in particularities in the reservoir diagenesis,hydrocarbon generation process and accumulation of deep-water area in northern South China Sea.展开更多
The easternmost Tian Shan lies in eastern Xinjiang, Central Asia. The South Barkol basin fault（SBF） in the northern part of the easternmost Tian Shan is a major tectonic structure in this orogenic region. The late Q...The easternmost Tian Shan lies in eastern Xinjiang, Central Asia. The South Barkol basin fault（SBF） in the northern part of the easternmost Tian Shan is a major tectonic structure in this orogenic region. The late Quaternary activity, paleoseismology, and deformation characteristics of the fault provide important clues for understanding the tectonic process of the eastern Tian Shan orogen and implementing seismic mitigation. Through interpretation of high-resolution satellite images, unmanned aerial vehicle measurements, and detailed geological and geomorphic investigations, we suggest that the fault exhibits clear left-lateral slip along its western segment. Paleoseismic trenches dug near Xiongkuer reveal evidence of six large paleoearthquakes. The four latest paleoearthquakes were dated： the oldest event occurred at 4663 BC–3839 BC. Data on the horizontal offsets along the probable 1842 Barkol earthquake coseismic rupture suggest clear multiple relationships between cumulative offsets and possible ~4 m of coseismic left-lateral slip per event. From the cumulative offsets and 14 C sample ages, we suggest an average Holocene left-lateral slip rate of 2.4–2.8 mm/a on the SBF, accounting for ~80% of lateral deformation within the entire eastern Tian Shan fault system. This result is comparable with the shortening rate of 2–4 mm/a in the whole eastern Tian Shan, indicating an equal role of strike-slip tectonics and compressional tectonics in this orogen, and that the SBF may accommodate substantial lateral tectonic deformation.展开更多
基金The research and development project of Beijing Disaster Prevention Technology Co.,Ltd.(FZKJYF202201)funded this work.
文摘Although the late Quaternary slip rate of the Northern Margin Fault of the Huaizhuo Basin(NFHB)was studied approximately 30 years ago using thermoluminescence and geomorphic methods,the underlying uncertainty cannot be neglected,considering the limitations resulting from age and displacement measurements.Accordingly,we attempted to re-estimate the late Quaternary slip rate of the NFHB using high-precision remote sensing image interpretation,large-scale geological and geomorphic mapping,paleoseismic analysis,and Quaternary geochronology testing.The results,based on stratigraphic dislocation and age constraint in the trenches,show that the present deformation of the NFHB has been dominated by the extension,with a vertical slip rate~0.04-0.11 mm/a.We estimate a vertical slip rate of~0.06 mm/a,with an R^(2) value of~0.91,which is much lower than the~0.5 mm/a result estimated previously.There are three possible reasons for this discrepancy.The first is the limitation resulting from dating and displacement measurements in earlier studies;the second is the slip decomposition caused by multiple branches of the NFHB,which leads to the low slip rate observed at a single fault;and third possible explanation is that the fault may be locked at present with a low slip rate,which means that the earthquake hazard of the NFHB cannot be ignored,and more in-depth research,such as geodetic and intensive observations of earthquake precursors,is urgently needed.This discovery poses a new challenge for the active study of the NFHB and the northeast corner of the Ordos Plateau in the North China Block.
基金supported jointly by the China Geological Survey project(grant number:1212011120167,12120114002201)China National Natural Science Foundation(grant number 41472178)
文摘We present in this paper some new evidence for the change during the Quaternary in kinematics of faults cutting the eastern margin of the Tibetan Plateau. It shows that significant shortening deformation occurred during the Early Pleistocene, evidenced by eastward thrusting of Mesozoic carbonates on the Pliocene lacustrine deposits along the Minjiang upstream fault zone and by development of the transpressional ridges of basement rocks along the Anninghe river valley. The Middle Pleistocene seems to be a relaxant stage with local development of the intra-mountain basins particularly prominent along the Minjiang Upstream and along the southern segment of the Anninghe River Valley. This relaxation may have been duo to a local collapse of the thickened crust attained during the late Neogene to early Pleistocene across this marginal zone. Fault kinematics has been changed since the late Pleistocene, and was predominated by reverse sinistral strike-slip along the Minshan Uplift, reverse dextral strike-slip on the Longmenshan fault zone and pure sinistral strike-slip on the Anninghe fault. This change in fault kinematics during the Quaternary allows a better understanding of the mechanism by which the marginal ranges of the plateau has been built through episodic activities.
基金supported by the National Science Foundation of China (grant No. 41472204)
文摘Objective The lateral extrusion eastward of the Tibetan Plateau leads to the formation of the Sichuan–Yunnan block, which is the most representative active block in the southeastern margin of the Tibetan Plateau, characterized by strong and frequent seismicity(Li Ping et al., 1975; Zhang Peizhen et al., 2003; Li Yong et al., 2017). Its eastern boundary is composed of sinistral faults including the Xianshuihe, Xiaojiang faults, etc., and the western
文摘Based on the Chinese mainland GPS network (1994~1996), Fujian GPS network (1995~1997), cross fault deformation network (1982-1998), precise leveling network (1973~1980) and focal mechanism solutions of the recent several tens years, we synthetically and quantitatively studied the present-time crustal motion of the southeast coast of Chinese mainland-Fujian and its marginal sea. We find that this area with its mainland together moves toward SE with a rather constant velocity of 11 .2±3.0 mm/a. At the same time, there is a motion from the Quanzhou bay pointing to hinterland, with a major orientation of NW, extending toward two sides, and with an average velocity of 3.0±2.6 mm/a. The faults orienting NE show compressing motions, and the ones orienting NW show extending motions. The present-time strain field derived from crustal deformation is consistent with seismic stress field derived from the focal mechanism solutions and the tectonic stress field derived from geology data. The principal stress of compression orients NW (NWW) - SE (SEE). Demarcated by the NW orienting faults of the Quanzhou bay and Jinjiang-Yongan, the crustal motions show regional characteristics f the southwest of Fujian and the boundary of Fujian and Guangdong are areas of rising, the northeast of Fujian are areas of sinking. The horizontal strain rate and the fault motion of the former are both greater than the later. The side-transferring motion of Hymalaya collision zone and the compression of the west pacific subduction zone affect the motion of the research area. The amount of motion affected by the former is larger than the later, but the former is homogeneous and the later is not, which indicates that the events of strong earthquakes in this region relate more directly with western pacific subduction zone.
基金supported by the Grant Agency of Charles University (43-258020)the Czech Science Foundation (250/09/1244)the Institute of Rock Structure and Mechanics AS CR, v.v.i. (A VOZ30460519)
文摘This study emphasizes the advantage of tectonic phase separation in determination of a tectonic evolution of complicated fault zones. The research focused on the Sudetic Marginal Fault Zone(SMFZ) –a 250 km long active fault zone with documented intraplate seismicity situated on the NE margin of the Bohemian Massif(the Czech Republic). The tectonic history of the SMFZ as well as its kinematic development has been rather complicated and not quite understood. A field structural investigation was carried out in extensive surroundings of the fault zone. The fault-slip data were collected in a number of natural outcrops and quarries with the aim at establishing a robust and field-constrained model for local brittle structural evolution of the studied area. A paleostress analysis was calculated using the collected fault-slip data inversion. The T-Tecto software was utilized for semiautomatic separation of the paleostress phases. Simultaneously three methods of data separation were employed:(1) the Gauss inverse method,(2) the Visualization of Gauss object Function, and(3) the frequency analysis. Within the fault zone multiphase movements were observed on various types of faults as well as wide range of the kinematic indicators orientations. The frequency analysis confirmed the multiphase history of the SMFZ. The calculated tectonic phases were divided according to their relative age as constrained by cross cutting relationships and, where observed, multiple striations on a single fault plane and classified from the oldest to the younger. Data separation and inversion usingT-Tecto software with the Gauss inverse method revealed four different stress phases which are 3 strike-slip stress regimes and one compressional regime. The strike-slip regimes are characterized by σ1 trending NW-SE(43), NNE-SSW(18), ENE-WSW(76) and the compressional one by σ1 trending W-E(26). First, compression occurred parallel to the SMFZ supposedly during the Variscan period. Second, compression at an angle of 60° to general direction of the SMFZ yielded right-lateral movement along the fault zone. This is considered to have occurred during the late-Variscan and post-Variscan period. Third, compression in the W-E direction with almost vertical extension led to reverse movement along the fault zone. This is considered to have occurred during Cenozoic. Fourth, compression almost perpendicular to the SMFZ led to left-lateral transpression along the SMFZ. This is considered to have occurred during Quaternary.
基金funded by the Special Project of Basic Work of Science and Technology“Compilation and dataprocessing of modern vertical deformation Atlas of Chinese mainland”(2015FY210400)the Science and Technology Innovation Fund(FMC2015013)of the First Crust Monitoring and Application Center,China Earthquake Administration
文摘Fault deformation characteristics in the northern margin of the Tibetan Plateau before the Menyuan Ms6.4 earthquake are investigated through time-series and structural geological analysis based on cross-fault observation data from the Qilian Mountain-Haiyuan Fault belt and the West Qinling Fault belt. The results indicate： 1） Group short-term abnormal variations appeared in the Qilian Mountain-Haiyuan Fault belt and the West Qinling Fault belt before the Menyuan Ms6.4 earthquake. 2） More medium and short-term anomalies appear in the middle-eastern segment of the Qilian Mountain Fault belt and the West Qinling Fault belt, suggesting that the faults＇ activities are strong in these areas. The faults＇ activities in the middle-eastern segment of the Qilian Fault belt result from extensional stress, as before the earthquake, whereas those in the West Qinling Fault belt are mainly compressional. 3） In recent years, moderate-strong earthquakes occurred in both the Kunlun Mountain and the Qilian Mountain Fault belts, and some energy was released. It is possible that the seismicity moved eastward under this regime. Therefore, we should pay attention to the West Qinling Mountain area where an Ms6-7 earthquake could occur in future.
文摘The formation of strath and strath terrace is closely related to tectonic uplift in the drainage basin. Based on the investigation of straths at Yandantu and Changcaogou on the eastern segment of the northern margin fault of Altun, and in combination with the paleoclimatic data, the tectonic uplift since late Epipleistocene as revealed by stream terraces at the two places is discussed. At Yandantu, three levels of stream terraces(T 1, T 2 and T 3)have developed since 16ka BP, where T 1, T 3 and T 2 are fill terraces and the buried major straths are exposed. The ages of three treads are dated to be about 16.1ka BP, 12.8ka BP and 6.2ka BP, respectively. The three terraces reflect three tectonic uplift events, while the ages of the treads represent the occurrence time of these events. The stream is still beveling the bedrock and widening the channel at present, and the modern strath is being generated. The uplift rate is 4.8～4.5mm/a since 16.1 ka BP in this area. From 12.8ka B.P to 6.2ka BP, The uplift rate was 6.4mm/a. The uplift rate is 3.1mm/a since 6.2ka BP. At Changcaogou, four levels of stream terraces(T 1, T 2, T 3 and T 1′)have developed since 7ka BP. All of them are fill terraces. There are buried straths under the deposits. The buried major strath is exposed on T 3 and T 2 and the minor strath on T 1′and T 1. The ages of treads of the three terraces (T 3, T 2 and T 1′) are 7 ka BP, 3 ka BP and 2.5 ka BP, respectively. The four terraces reflect two uplift events induced by tectonic activities. One occurred in about 7 ka BP, and the other in 3ka BP. The uplift rate is 5.9mm/a since 7.0 ka BP at Changcaogou. From 7ka BP to 3ka BP, the uplift rate was 7.0mm/a, and since 3ka BP till now, the uplift rate is 4.7 mm/a.
基金funded by the Special Fund for Basic Scientific Research of Institute of Earthquake Science,China Earthquake Administration(2015 IES010202)the Seismic Risk Assessment Project for Active Faults in Key Region of Earthquake Monitoring and Prevention in China(201210916)
文摘The Yuguang basin is a half-graben basin in the basin-range tectonic zone in northwest Beijing,located at the northern end of the Shanxi graben system,and the Yuguang basin southern marginal fault( YBSMF) controls the formation of this basin. A linear fault escarpment has formed in the proluvial fan on the piedmont fault zone of the Tangshankou segment of YBSMF. A trench across this escarpment reveals three paleo-earthquake events on two active faults. One fault ruptured at about 9 ka for the first time,and then faulted again at about 7. 3 ka,causing the formation and synchronous activity of another fault.Finally,they faulted for the third time,but we cannot determine the faulting time due to the lack of relevant surface deposition. The accumulative vertical displacement of these three events is about 8. 1 m. We estimate that the average recurrence period of the piedmont fault is about 1. 7 ka,and the average slip rate of the piedmont fault is about1. 6 mm/a. We also estimate the reference magnitude of each event according to the empirical formula.
基金supported by a geological survey project of the China Geological Survey(No.1212011140013,No.12120113009800,No.121201010000150001)
文摘The geology and tectonics in the eastern margin of Tibetan Plateau are complex. The main tectonic framework is composed of blocks and faults. Using discontinuous global positioning system survey data for 2008–2014, the velocity field for the Eurasia reference framework was obtained. Based on the velocity field, the present-day velocities of the blocks and boundary faults were estimated. The results reveal that the movement rates of the Chuan-Qing, South China, Chuan-Dian and Indo-China blocks are（17.02±0.60） mm/a,（8.77±1.51） mm/a,（13.85±1.31） mm/a and（6.84 ± 0.74） mm/a, respectively, and their movement directions are 99.5°, 120.3°, 142.9° and 153.3°, respectively. All blocks exhibit clockwise rotation. The displacement rates of the Xianshuihe, Longmenshan, Anninghe, Zemuhe, Xiaojiang and Red River faults are（7.30±1.25–8.30±1.26） mm/a,（10.07±0.97–11.79±0.89） mm/a,（0.96±0.74–2.98±1.73） mm/a,（2.03±0.49–3.20±0.73） mm/a,（3.45±0.40–6.02±0.50） mm/a and（6.23±0.56） mm/a, respectively. The Xianshuihe, Anninghe, Zemuhe and Xiaojiang faults show leftlateral strike-slip movement, while the Longmenshan and Red River faults show right-lateral strikeslip. These characteristics of the blocks and faults are related to the particular tectonic location and dynamic mechanism.
基金Acknowledgements This research was supported by the National Natural Science Foundation of China under contract Nos 40476026 and 40406012, the National Natural Science Foundation of Guangdong Province under contract No. 04001309, and the Key Laboratory of Marginal Sea Geology Foundation of South China Sea Institute of 0ceanology, Chinese Academy of Sciences under contract No. MSGL0510. We are grateful to Yan Pin and Liu Hailing for their generous help in providing seismic profiles.
文摘The western fault zone of the South China Sea is a strike-slip fault system and consists of four typical strike-slip faults. It is the western border of the South China Sea. The formation of the system is due to the extrusion of Indo - China Peninsula caused by the collision of India with Tibet and the spreading of the South China Sea in Cenozoic. There are five episodes of tectonic movement along this fault zone, which plays an important role in the Cenozoic evolution of the South China Sea. By the physical modeling experiments, it can be seen the strike-slip fault undergoes the sinistral and dextral movement due to the relative movement velocity change between the South China Sea block and the Indo - China block. The fault zone controls the evolution of the pull basins locating in the west of the South China Sea.
基金Supported by the Science and Technology Project of CNOOC Ltd.(YXKY-2012-SHENHAI-01)China National Science and Technology Major Project(2011ZX05025-003+1 种基金 2016ZX05026-003)the National Natural Science Foundation of China(91128207)
文摘The relationships between crustal stretching and thinning,basin structure and petroleum geology in Baiyun deep-water area were analyzed using large area 3D seismic,gravity,magnetic,ocean bottom seismic(OBS),deep-water exploration wells and integrated ocean drilling program(IODP).During the early syn-rifting period,deep-water area was a half-graben controlled by high angle faults influenced by the brittle extension of upper crust.In the mid syn-rifting period,this area was a broad-deep fault depression controlled by detachment faults undergone brittle-ductile deformation and differentiated extension in the crust.In the late syn-rifting period,this area experienced fault-sag transition due to saucer-shaped rheology change dominated by crustal ductile deformation.A broad-deep fault depression controlled by the large detachment faults penetrating through the crust is an important feature of deep-water basin.The study suggests that the broad-deep Baiyun sag provides great accommodation space for the development of massive deltaic-lacustrine deposition system and hydrocarbon source rocks.The differentiated lithospheric thinning also resulted in the different thermal subsidence during post-rifting period,and then controlled the development of continental shelf break and deep-water reservoir sedimentary environment.The high heat flow background caused by the strong thinning of lithosphere and the rise of mantle source resulted in particularities in the reservoir diagenesis,hydrocarbon generation process and accumulation of deep-water area in northern South China Sea.
基金funded by foundation of seismic risk assessment of active faults,China Earthquake Administration(Grant no.1521044025)
文摘The easternmost Tian Shan lies in eastern Xinjiang, Central Asia. The South Barkol basin fault（SBF） in the northern part of the easternmost Tian Shan is a major tectonic structure in this orogenic region. The late Quaternary activity, paleoseismology, and deformation characteristics of the fault provide important clues for understanding the tectonic process of the eastern Tian Shan orogen and implementing seismic mitigation. Through interpretation of high-resolution satellite images, unmanned aerial vehicle measurements, and detailed geological and geomorphic investigations, we suggest that the fault exhibits clear left-lateral slip along its western segment. Paleoseismic trenches dug near Xiongkuer reveal evidence of six large paleoearthquakes. The four latest paleoearthquakes were dated： the oldest event occurred at 4663 BC–3839 BC. Data on the horizontal offsets along the probable 1842 Barkol earthquake coseismic rupture suggest clear multiple relationships between cumulative offsets and possible ~4 m of coseismic left-lateral slip per event. From the cumulative offsets and 14 C sample ages, we suggest an average Holocene left-lateral slip rate of 2.4–2.8 mm/a on the SBF, accounting for ~80% of lateral deformation within the entire eastern Tian Shan fault system. This result is comparable with the shortening rate of 2–4 mm/a in the whole eastern Tian Shan, indicating an equal role of strike-slip tectonics and compressional tectonics in this orogen, and that the SBF may accommodate substantial lateral tectonic deformation.
