Fold-thrust belts are common structural styles under the background of long-term regional tectonic shortening.The northern and northeastern margins of the Qinghai-Tibetan Plateau are located on the edge of the growth ...Fold-thrust belts are common structural styles under the background of long-term regional tectonic shortening.The northern and northeastern margins of the Qinghai-Tibetan Plateau are located on the edge of the growth and expansion of the Qinghai-Tibetan Plateau.Since nearly 10 Ma,some significant and typical fold thrust belt have been formed.The spatial-temporal evolution of these fold-thrust belts and the characteristics of surface deformations are significant issues in geodynamics.In this paper,we use the elastoplastic finite element model with considering the contact nonlinearity to study the spatialtemporal evolution of the fold-thrust belts in the northern and northeastern margins of the Qinghai-Tibetan Plateau,with particular attention to the details of the relationship between the depth and the shallow,the spatialtemporal order,and the characteristics of the surface deformation,etc.,in order to make a relatively complete mechanical interpretation of the spatial-temporal evolution of the foldthrust belts in the northern and northeastern margins of the Qinghai-Tibetan Plateau from the perspective of geodynamics.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 Mountaine Haiyuan Fault belt and the West Qinling Fault belt. The results indicate: 1) Group short-term abnormal variations appeared in the Qilian Mountaine 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
Project INDEPTH(Inter National DEep Profiling of Tibet and the Himalaya) is an interdisciplinary program designed to develop a better understanding of deep structures and mechanics of the Tibetan Plateau. As a compone...Project INDEPTH(Inter National DEep Profiling of Tibet and the Himalaya) is an interdisciplinary program designed to develop a better understanding of deep structures and mechanics of the Tibetan Plateau. As a component of magnetotelluric(MT) work in the 4th phase of the project, MT data were collected along a profile that crosses the eastern segment of the Altyn Tagh fault on the northern margin of the plateau. Time series data processing used robust algorithms to give high quality responses. Dimensionality analysis showed that 2D approach is only valid for the northern section of the profile. Consequently, 2D inversions were only conducted for the northern section, and 3D inversions were conducted on MT data from the whole profile. From the 2D inversion model, the eastern segment of the Altyn Tagh fault only appears as a crustal structure, which suggests accommodation of strike slip motion along the Altyn Tagh fault by thrusting within the Qilian block. A large-scale off-profile conductor within the mid-lower crust of the Qilian block was revealed from the 3D inversion model, which is probably correlated with the North Qaidam thrust belt. Furthermore, the unconnected conductors from the 3D inversion model indicate that deformations in the study area are generally localized.展开更多
The geological structure background, the crustal structure and the shape of Moho in the northeastern margin of the Qinghai-Tibetan plateau are studied. Based on artificial seismic sounding profile as well as geologica...The geological structure background, the crustal structure and the shape of Moho in the northeastern margin of the Qinghai-Tibetan plateau are studied. Based on artificial seismic sounding profile as well as geological data. The main results are summarized as follows: ( The geotectonic subdivisions and the characteristics of main deep and large faults in the northeastern margin of the Qinghai-Tibetan plateau are presented; ( The general features of the Moho are obtained mainly based on artificial seismic sounding data; ( There exists well corresponding relation between surface faults and some features of the Moho, which suggests that such complex crustal structure might be the preparation environment of strong earthquakes.展开更多
On September 5,2022,at Beijing time 12:52 p.m.,an M_(S)6.8 earthquake struck Luding County,GarzêTibetan Autonomous Prefecture,Sichuan Province.The epicenter of the earthquake was at the intersection of the Sichua...On September 5,2022,at Beijing time 12:52 p.m.,an M_(S)6.8 earthquake struck Luding County,GarzêTibetan Autonomous Prefecture,Sichuan Province.The epicenter of the earthquake was at the intersection of the Sichuan-Yunnan,Bayankala,and South China blocks.The tectonic background is extremely complex,and strong earthquakes occur frequently.Based on a predetermined focal location and focal mechanism solution for the earthquake,we reversed the focal depth and rupture process of the earthquake by fitting the teleseismic P and SH waves recorded by the global seismic network.The results show that the focal depth is 16 km,with the main rupture having a length of about 45 km near the epicenter,with a maximum displacement of 1.02 m.Although the rupture mainly propagates from the north–northwest(NNW)to the south–southeast(SSE)along the fault strike,there is a small-scale rupture slip zone at shallow depths in the north–northeast(NNE)direction along the epicenter of the seismogenic fault.This rupture image corresponds to the cluster distribution of aftershocks in the NNW and SSE directions starting from the epicenter,corresponding to the distribution of recorded landslides.The earthquake occurred on the Moxi fault,located in the southeastern section of the Xianshuihe fault.The major tectonic feature in this area is the southeastward movement of the Chuandian block relative to the Bayanhar block.展开更多
New data of oxygen and carbonate isotope in calcite cements from Cenozoic rocks in the Jianggelesayi area to reconstruct the uplift history of mountains in northern edge of the Qinghai-Tibetan Plateau are presented. A...New data of oxygen and carbonate isotope in calcite cements from Cenozoic rocks in the Jianggelesayi area to reconstruct the uplift history of mountains in northern edge of the Qinghai-Tibetan Plateau are presented. Analyses results show that rapid changes of Δ18o and Δ13c in the calcite cement occurred in both the Early Oligocene and Early Miocene. Studies on sedimentary features indicate that a rapid up-coarsing of the sediments size occurred in the Early Miocene, and sedimentary velocity increased rapidly during the Pliocene and Early Quaternary. Thus, it is suggested that the uplift of mountains in the northern edge of the Qinghai-Tibetan Plateau initiated from the Early Oligocene, and a rapid uplift occurred in the early stage of the Miocene, while the sharp difference in topography between the northern plateau and the Tarim Basin predominately formed later than the Miocene.展开更多
Decoding the variation laws of the deformation field before strong earthquakes has long been recognized as an essential issue in earthquake prediction research. In this paper, the temporal and spatial distribution cha...Decoding the variation laws of the deformation field before strong earthquakes has long been recognized as an essential issue in earthquake prediction research. In this paper, the temporal and spatial distribution characteristics of deformation anomalies in the northeastern margin of the Qinghai-Tibetan Plateau before and after the Menyuan M_(S)6.9 earthquake were studied by using the Fisher statistical test method. By analyzing the characteristics of these anomalies, we found that: 1) The deformation anomalies are mainly distributed in the marginal front area of the Qinghai-Tibetan Plateau, where short-term deformation anomalies are prone to occur due to a high gradient of gravity;2) The deformation anomalies along the northeastern margin of the Qinghai-Tibetan Plateau are characterized by spatial propagation, and the migration rate is about 2.4 km/d. The propagation pattern is counterclockwise, consistent with the migration direction of M_(S)≥ 6.0 earthquakes;3) The time and location of the Menyuan earthquake are related to the group migration of earthquakes with M_(S)≥ 6.0. Finally,based on the results of gravity field variation and the theory of crust stress wave, the law of deformation anomaly distribution was discussed. We suggest that both the deformation propagation along the northeastern margin of the Qinghai-Tibetan Plateau and the earthquake migration are possibly associated with the variation of the stress field caused by subsurface mass flow.展开更多
基金financially supported by the National Science Foundation of China (42074117)supported by the Fundamental Research Funds for the Central Universities。
文摘Fold-thrust belts are common structural styles under the background of long-term regional tectonic shortening.The northern and northeastern margins of the Qinghai-Tibetan Plateau are located on the edge of the growth and expansion of the Qinghai-Tibetan Plateau.Since nearly 10 Ma,some significant and typical fold thrust belt have been formed.The spatial-temporal evolution of these fold-thrust belts and the characteristics of surface deformations are significant issues in geodynamics.In this paper,we use the elastoplastic finite element model with considering the contact nonlinearity to study the spatialtemporal evolution of the fold-thrust belts in the northern and northeastern margins of the Qinghai-Tibetan Plateau,with particular attention to the details of the relationship between the depth and the shallow,the spatialtemporal order,and the characteristics of the surface deformation,etc.,in order to make a relatively complete mechanical interpretation of the spatial-temporal evolution of the foldthrust belts in the northern and northeastern margins of the Qinghai-Tibetan Plateau from the perspective of geodynamics.
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 Mountaine Haiyuan Fault belt and the West Qinling Fault belt. The results indicate: 1) Group short-term abnormal variations appeared in the Qilian Mountaine 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.
基金supported by grants from the National Natural Science Foundation of China(General Program No.40974058)National Science Fund for Distinguished Young Scholars(No.40904025 and 41404060)+4 种基金Fundamental Research Funds for the Central Universities(2652014016)National Natural Science Foundation of ChinaUnited States National Science FoundationScience Foundation of Ireland(award 08/RFP/GEO1693 to AGJ)Natural Science and Engineering Research Council(Canada)for financial support
文摘Project INDEPTH(Inter National DEep Profiling of Tibet and the Himalaya) is an interdisciplinary program designed to develop a better understanding of deep structures and mechanics of the Tibetan Plateau. As a component of magnetotelluric(MT) work in the 4th phase of the project, MT data were collected along a profile that crosses the eastern segment of the Altyn Tagh fault on the northern margin of the plateau. Time series data processing used robust algorithms to give high quality responses. Dimensionality analysis showed that 2D approach is only valid for the northern section of the profile. Consequently, 2D inversions were only conducted for the northern section, and 3D inversions were conducted on MT data from the whole profile. From the 2D inversion model, the eastern segment of the Altyn Tagh fault only appears as a crustal structure, which suggests accommodation of strike slip motion along the Altyn Tagh fault by thrusting within the Qilian block. A large-scale off-profile conductor within the mid-lower crust of the Qilian block was revealed from the 3D inversion model, which is probably correlated with the North Qaidam thrust belt. Furthermore, the unconnected conductors from the 3D inversion model indicate that deformations in the study area are generally localized.
基金National Key Research Development Project(95-13-02-02).Contribution No.LC2000052,Lanzhou Institute of Seismology,China SeismologicalBureau.
文摘The geological structure background, the crustal structure and the shape of Moho in the northeastern margin of the Qinghai-Tibetan plateau are studied. Based on artificial seismic sounding profile as well as geological data. The main results are summarized as follows: ( The geotectonic subdivisions and the characteristics of main deep and large faults in the northeastern margin of the Qinghai-Tibetan plateau are presented; ( The general features of the Moho are obtained mainly based on artificial seismic sounding data; ( There exists well corresponding relation between surface faults and some features of the Moho, which suggests that such complex crustal structure might be the preparation environment of strong earthquakes.
基金the Central Publicinterest Scientific Institution Basal Research Fund(2021IEF0501 and CEAIEF20220205)the National Natural Science Foundation of China(42074100).
文摘On September 5,2022,at Beijing time 12:52 p.m.,an M_(S)6.8 earthquake struck Luding County,GarzêTibetan Autonomous Prefecture,Sichuan Province.The epicenter of the earthquake was at the intersection of the Sichuan-Yunnan,Bayankala,and South China blocks.The tectonic background is extremely complex,and strong earthquakes occur frequently.Based on a predetermined focal location and focal mechanism solution for the earthquake,we reversed the focal depth and rupture process of the earthquake by fitting the teleseismic P and SH waves recorded by the global seismic network.The results show that the focal depth is 16 km,with the main rupture having a length of about 45 km near the epicenter,with a maximum displacement of 1.02 m.Although the rupture mainly propagates from the north–northwest(NNW)to the south–southeast(SSE)along the fault strike,there is a small-scale rupture slip zone at shallow depths in the north–northeast(NNE)direction along the epicenter of the seismogenic fault.This rupture image corresponds to the cluster distribution of aftershocks in the NNW and SSE directions starting from the epicenter,corresponding to the distribution of recorded landslides.The earthquake occurred on the Moxi fault,located in the southeastern section of the Xianshuihe fault.The major tectonic feature in this area is the southeastward movement of the Chuandian block relative to the Bayanhar block.
基金supported by the National Natural Science Foundation of China(Grant No.40102022)the Major State Basic Research Program of China(Grant Nos.2001CB409808 and 2001CB7110013).
文摘New data of oxygen and carbonate isotope in calcite cements from Cenozoic rocks in the Jianggelesayi area to reconstruct the uplift history of mountains in northern edge of the Qinghai-Tibetan Plateau are presented. Analyses results show that rapid changes of Δ18o and Δ13c in the calcite cement occurred in both the Early Oligocene and Early Miocene. Studies on sedimentary features indicate that a rapid up-coarsing of the sediments size occurred in the Early Miocene, and sedimentary velocity increased rapidly during the Pliocene and Early Quaternary. Thus, it is suggested that the uplift of mountains in the northern edge of the Qinghai-Tibetan Plateau initiated from the Early Oligocene, and a rapid uplift occurred in the early stage of the Miocene, while the sharp difference in topography between the northern plateau and the Tarim Basin predominately formed later than the Miocene.
基金sponsored by the National Natural Science Foundation of China (41330314)。
文摘Decoding the variation laws of the deformation field before strong earthquakes has long been recognized as an essential issue in earthquake prediction research. In this paper, the temporal and spatial distribution characteristics of deformation anomalies in the northeastern margin of the Qinghai-Tibetan Plateau before and after the Menyuan M_(S)6.9 earthquake were studied by using the Fisher statistical test method. By analyzing the characteristics of these anomalies, we found that: 1) The deformation anomalies are mainly distributed in the marginal front area of the Qinghai-Tibetan Plateau, where short-term deformation anomalies are prone to occur due to a high gradient of gravity;2) The deformation anomalies along the northeastern margin of the Qinghai-Tibetan Plateau are characterized by spatial propagation, and the migration rate is about 2.4 km/d. The propagation pattern is counterclockwise, consistent with the migration direction of M_(S)≥ 6.0 earthquakes;3) The time and location of the Menyuan earthquake are related to the group migration of earthquakes with M_(S)≥ 6.0. Finally,based on the results of gravity field variation and the theory of crust stress wave, the law of deformation anomaly distribution was discussed. We suggest that both the deformation propagation along the northeastern margin of the Qinghai-Tibetan Plateau and the earthquake migration are possibly associated with the variation of the stress field caused by subsurface mass flow.
