A near NS-strike east-dipping normal fault is developed on the western side of Wenquan graben in the central Qinghal-Xizang（Tibet） Plateau. It is the western marginal fault of the graben and has been intensely activ...A near NS-strike east-dipping normal fault is developed on the western side of Wenquan graben in the central Qinghal-Xizang（Tibet） Plateau. It is the western marginal fault of the graben and has been intensely active. It is a product of the near EW extension and deformation of the central northern Qinghal-Xizang（Tibet） Plateau since the late Cenozoic under the effect of the collision of the India and Eurasia plates. Since the late Cenozoic, the maximum vertical displacement on the fault was greater than 2. ! km, and the dislocated Mesozoic fold stratum reveals a maximum accumulative throw of 6.0 ± 2.2km. Quaternary faulting took place many times along the fault, creating multi-set piedmont fault facets and multi-level fault scarplets.According to the height of fault scarps that result from the vertical offset of the late Quaternary strata and geomorphic provinces, the maximum slip rate of the fault is estimated to have been less than 1.2mm/a since the late Quaternary, averaging 0.45mm/a. The trenching across the fault reveals that at least 3 paleoearthquakes of varied magnitudes have occurred since the late Epipleistocene. In view of the characteristics of Cenozoic faulting, it is concluded that the fault will act as a dominant seismogenic fault for earthquakes of M6.0 to M7.0 that are most likely to occur in the future.展开更多
文摘A near NS-strike east-dipping normal fault is developed on the western side of Wenquan graben in the central Qinghal-Xizang（Tibet） Plateau. It is the western marginal fault of the graben and has been intensely active. It is a product of the near EW extension and deformation of the central northern Qinghal-Xizang（Tibet） Plateau since the late Cenozoic under the effect of the collision of the India and Eurasia plates. Since the late Cenozoic, the maximum vertical displacement on the fault was greater than 2. ! km, and the dislocated Mesozoic fold stratum reveals a maximum accumulative throw of 6.0 ± 2.2km. Quaternary faulting took place many times along the fault, creating multi-set piedmont fault facets and multi-level fault scarplets.According to the height of fault scarps that result from the vertical offset of the late Quaternary strata and geomorphic provinces, the maximum slip rate of the fault is estimated to have been less than 1.2mm/a since the late Quaternary, averaging 0.45mm/a. The trenching across the fault reveals that at least 3 paleoearthquakes of varied magnitudes have occurred since the late Epipleistocene. In view of the characteristics of Cenozoic faulting, it is concluded that the fault will act as a dominant seismogenic fault for earthquakes of M6.0 to M7.0 that are most likely to occur in the future.
