Double-sided subduction with contrasting polarities beneath the Pamir-Hindu Kush:Evidence from focal mechanism solutions and stress field inversion  

作　　者：Yu Yang Zuoxun Zeng Scott D.King Xiao Shuang 

机构地区：[1]School of Earth Sciences,China University of Geosciences(Wuhan),Wuhan 430074,China [2]Huazhong Tectonomechanical Research Center,China University of Geosciences(Wuhan),Wuhan 430074,China [3]Department of Geosciences,Virginia Tech,Blacksburg,VA 24061,USA [4]Fuyang Branch of Hangzhou Bureau of Planning and Natural Resources,Hangzhou 311499,China

出　　处：《Geoscience Frontiers》2022年第4期98-113,共16页地学前缘（英文版）

基　　金：jointly supported by National 985 Platform construction project,China Geological Survey(Grant No.12120114002211);National Nature Science Foundation of China(Grant No.41230206);a fund of the Graduate School of the China University of Geosciences for visiting and conducting research abroad。

摘　　要：The Pamir-Hindu Kush region at the western end of the Himalayan-Tibet orogen is one of the most active regions on the globe with strong seismicity and deformation and provides a window to evaluate continental collision linked to two intra-continental subduction zones with different polarities.The seismicity and seismic tomography data show a steep northward subducting slab beneath the Hindu Kush and southward subducting slab under the Pamir.Here,we collect seismic catalogue with 3988 earthquake events to compute seismicity images and waveform data from 926 earthquake events to invert focal mechanism solutions and stress field with a view to characterize the subducting slabs under the Pamir-Hindu Kush region.Our results define two distinct seismic zones:a steep one beneath the Hindu Kush and a broad one beneath the Pamir.Deep and intermediate-depth earthquakes are mainly distributed in the Hindu Kush region which is controlled by thrust faulting,whereas the Pamir is dominated by strike-slip stress regime with shallow and intermediate-depth earthquakes.The area where the maximum principal stress axis is vertical in the southern Pamir corresponds to the location of a highconductivity low-velocity region that contributes to the seismogenic processes in this region.We interpret the two distinct seismic zones to represent a double-sided subduction system where the Hindu Kush zone represents the northward subduction of the Indian plate,and the Pamir zone shows southward subduction of the Eurasian plate.A transition fault is inferred in the region between the Hindu Kush and the Pamir which regulates the opposing directions of motion of the Indian and Eurasian plates.

关 键 词：Pamir-Hindu Kush SEISMICITY Stress field Double-sided subduction Low-velocity body 

分 类 号：P315.7[天文地球—地震学]