On 21 May 2021(UTC),an MW 7.4 earthquake jolted the east Bayan Har block in the Tibetan Plateau.The earthquake received widespread attention as it is the largest event in the Tibetan Plateau and its surroundings since...On 21 May 2021(UTC),an MW 7.4 earthquake jolted the east Bayan Har block in the Tibetan Plateau.The earthquake received widespread attention as it is the largest event in the Tibetan Plateau and its surroundings since the 2008 Wenchuan earthquake,and especially in proximity to the seismic gaps on the east Kunlun fault.Here we use satellite interferometric synthetic aperture radar data and subpixel offset observations along the range directions to characterize the coseismic deformation of the earthquake.Range offset displacements depict clear surface ruptures with a total length of~170 km involving two possible activated fault segments in the earthquake.Coseismic modeling results indicate that the earthquake was dominated by left-lateral strike-slip motions of up to 7 m within the top 12 km of the crust.The well-resolved slip variations are characterized by five major slip patches along strike and 64%of shallow slip deficit,suggesting a young seismogenic structure.Spatial-temporal changes of the postseismic deformation are mapped from early 6-day and 24-day InSAR observations,and are well explained by time-dependent afterslip models.Analysis of Global Navigation Satellite System(GNSS)velocity profiles and strain rates suggests that the eastward extrusion of plateau is diffusely distributed across the east Bayan Har block,but exhibits significant lateral heterogeneities,as evidenced by magnetotelluric observations.The block-wide distributed deformation of the east Bayan Har block along with the significant co-and post-seismic stress loadings from the Madoi earthquake imply high seismic risks along regional faults,especially the Tuosuo Lake and Maqên-Maqu segments of the Kunlun fault that are known as seismic gaps.展开更多
The Bayan Har block is mainly bounded by the east Kunlun fault zone to the north, Garze-Yushu -Xianshuihe fault zone to the south and Longmenshan fault zone to the east （Fig. 1）. In the past 20 years, large earthqua...The Bayan Har block is mainly bounded by the east Kunlun fault zone to the north, Garze-Yushu -Xianshuihe fault zone to the south and Longmenshan fault zone to the east （Fig. 1）. In the past 20 years, large earthquakes have occurred frequently along this block＇s boundaries, which has received much attention among geoscientists. Whether large earthquakes will happen （and where） along this block＇s boundary faults in the future are two key problems that need to be addressed. This study calculates the accumulated tectonic stress and superposition of the coulomb stress caused by fault slip of 16 large earthquakes since 1904, and evaluates the possible locations of future earthquakes that may occur around this block.展开更多
At 02:04 on May 22,2021,an M_(S)7.4 earthquake occurred in Madoi County in Qinghai Province,China.This earthquake is the largest seismic event in China since the 2008M_(S) 8.0 Wenchuan earthquake.Thus,it is critical t...At 02:04 on May 22,2021,an M_(S)7.4 earthquake occurred in Madoi County in Qinghai Province,China.This earthquake is the largest seismic event in China since the 2008M_(S) 8.0 Wenchuan earthquake.Thus,it is critical to investigate surface deformation and damage in time to accurately understand the seismogenic structure of the Madoi earthquake and the seismogenic capacity of the blocks in this region.This study focuses on the Xuema Village,located at the eastern end of the coseismic surface ruptures produced by the event,and assesses the deformation and seismic damage in this area based on field surveys,UAV photogrammetry,and ground penetrating radar(GPR).The results indicate that the rupture scale is substantially smaller at the eastern end of the rupture zone compared to other segments.En echelon type shear tensile fractures are concentrated in a width range of 50–100 m,and the width of single fractures ranges from 20 to 30 cm.In contrast,the degree of seismic damage significantly increases at this site.All of the brick and timber houses are damaged or collapsed,while the steel frame structures and the color steel houses are slightly damaged.More than 80%of the bridge decks on the Changma River Bridge collapse,similar to the terraces along the Youerqu and Changma Rivers and the cut slopes of Provincial Highway S205.We infer that the seismogenic fault of the Madoi earthquake exerts a tail effect in this segment.The tension zone has led to a reduction at the eastern end of the rupture zone,causing shaking damage.Local topography and buildings without earthquake-resistant construction along the strike of the rupture zone have undergone different levels of seismic damage.展开更多
Madoi-Gade fault is an active fault in the Bayan Har block. According to field investigation, there is an earthquake surface rupture fairly well preserved on the Gade segment of the Madoi-Gade fault zone. The length o...Madoi-Gade fault is an active fault in the Bayan Har block. According to field investigation, there is an earthquake surface rupture fairly well preserved on the Gade segment of the Madoi-Gade fault zone. The length of the rupture is approximately 50km, with a general strike of NW. The maximum horizontal sinistral displacement is about 7.6m and the maximum vertical displacement is about 4m. A large number of earthquake traces are to be found along the rupture zone, and the phenomena on the surface rupture are also various. Field investigation and analysis on the geological and geomorphological phenomena show that the formation age of the surface rupture is relatively young. A series of linear arranged, triangular facets, fault scarps, fault springs, dislocated gullies, twisted mountain ridges, sag-ponds, dislocated ridges, etc. exist along the fault. Based on the analysis of field investigation and the data available, we believe that the surface rupture is due to a strong earthquake in the history of this area. And it is inferred that the Madoi- Gade fault within the Bayan Har block has been highly active since Late Quaternary and may still be active nowadays.展开更多
基金supported by the Natural Science Foundation of Jiangsu Province(Grant No.SBK2020043202)by Key Laboratory of Geospace Environment and Geodesy,Ministry of Education,Wuhan University(No.19-01-08).
文摘On 21 May 2021(UTC),an MW 7.4 earthquake jolted the east Bayan Har block in the Tibetan Plateau.The earthquake received widespread attention as it is the largest event in the Tibetan Plateau and its surroundings since the 2008 Wenchuan earthquake,and especially in proximity to the seismic gaps on the east Kunlun fault.Here we use satellite interferometric synthetic aperture radar data and subpixel offset observations along the range directions to characterize the coseismic deformation of the earthquake.Range offset displacements depict clear surface ruptures with a total length of~170 km involving two possible activated fault segments in the earthquake.Coseismic modeling results indicate that the earthquake was dominated by left-lateral strike-slip motions of up to 7 m within the top 12 km of the crust.The well-resolved slip variations are characterized by five major slip patches along strike and 64%of shallow slip deficit,suggesting a young seismogenic structure.Spatial-temporal changes of the postseismic deformation are mapped from early 6-day and 24-day InSAR observations,and are well explained by time-dependent afterslip models.Analysis of Global Navigation Satellite System(GNSS)velocity profiles and strain rates suggests that the eastward extrusion of plateau is diffusely distributed across the east Bayan Har block,but exhibits significant lateral heterogeneities,as evidenced by magnetotelluric observations.The block-wide distributed deformation of the east Bayan Har block along with the significant co-and post-seismic stress loadings from the Madoi earthquake imply high seismic risks along regional faults,especially the Tuosuo Lake and Maqên-Maqu segments of the Kunlun fault that are known as seismic gaps.
基金supported by Geological Survey programs from Geological Survey of China(No.1212011120163 and 12120114002101)Basic Science Research Fund of the Institute of Geomechanics,CAGS (No.DZLXJK201212)National Natural Science Foundation of China (No.41171009)
文摘The Bayan Har block is mainly bounded by the east Kunlun fault zone to the north, Garze-Yushu -Xianshuihe fault zone to the south and Longmenshan fault zone to the east （Fig. 1）. In the past 20 years, large earthquakes have occurred frequently along this block＇s boundaries, which has received much attention among geoscientists. Whether large earthquakes will happen （and where） along this block＇s boundary faults in the future are two key problems that need to be addressed. This study calculates the accumulated tectonic stress and superposition of the coulomb stress caused by fault slip of 16 large earthquakes since 1904, and evaluates the possible locations of future earthquakes that may occur around this block.
基金This research was supported by the National Natural Science Foundation of China(42072248,42041006)the National Key Research and Development Program(2021YFC3000601-3,2019YFE0108900)Scientific Research Project of China Datang Corporation Ltd.(DTXZ-02-2021).
文摘At 02:04 on May 22,2021,an M_(S)7.4 earthquake occurred in Madoi County in Qinghai Province,China.This earthquake is the largest seismic event in China since the 2008M_(S) 8.0 Wenchuan earthquake.Thus,it is critical to investigate surface deformation and damage in time to accurately understand the seismogenic structure of the Madoi earthquake and the seismogenic capacity of the blocks in this region.This study focuses on the Xuema Village,located at the eastern end of the coseismic surface ruptures produced by the event,and assesses the deformation and seismic damage in this area based on field surveys,UAV photogrammetry,and ground penetrating radar(GPR).The results indicate that the rupture scale is substantially smaller at the eastern end of the rupture zone compared to other segments.En echelon type shear tensile fractures are concentrated in a width range of 50–100 m,and the width of single fractures ranges from 20 to 30 cm.In contrast,the degree of seismic damage significantly increases at this site.All of the brick and timber houses are damaged or collapsed,while the steel frame structures and the color steel houses are slightly damaged.More than 80%of the bridge decks on the Changma River Bridge collapse,similar to the terraces along the Youerqu and Changma Rivers and the cut slopes of Provincial Highway S205.We infer that the seismogenic fault of the Madoi earthquake exerts a tail effect in this segment.The tension zone has led to a reduction at the eastern end of the rupture zone,causing shaking damage.Local topography and buildings without earthquake-resistant construction along the strike of the rupture zone have undergone different levels of seismic damage.
基金supported by the National Basic Research Program(973 program) of China(Grant No.2008CB425701)
文摘Madoi-Gade fault is an active fault in the Bayan Har block. According to field investigation, there is an earthquake surface rupture fairly well preserved on the Gade segment of the Madoi-Gade fault zone. The length of the rupture is approximately 50km, with a general strike of NW. The maximum horizontal sinistral displacement is about 7.6m and the maximum vertical displacement is about 4m. A large number of earthquake traces are to be found along the rupture zone, and the phenomena on the surface rupture are also various. Field investigation and analysis on the geological and geomorphological phenomena show that the formation age of the surface rupture is relatively young. A series of linear arranged, triangular facets, fault scarps, fault springs, dislocated gullies, twisted mountain ridges, sag-ponds, dislocated ridges, etc. exist along the fault. Based on the analysis of field investigation and the data available, we believe that the surface rupture is due to a strong earthquake in the history of this area. And it is inferred that the Madoi- Gade fault within the Bayan Har block has been highly active since Late Quaternary and may still be active nowadays.
