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Along‐Strike and Downdip Segmentation of the Pamir Frontal Thrust and Its Association With the 1985 M w 6.9 Wuqia Earthquake
Author(s) -
Li Tao,
Chen Zhuxin,
Chen Jie,
Thompson Jobe Jessica A.,
Burbank Douglas W.,
Li Zhigang,
He Xiaohui,
Zheng Wenjun,
Zhang Peizhen,
Zhang Boxuan
Publication year - 2019
Publication title -
journal of geophysical research: solid earth
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.983
H-Index - 232
eISSN - 2169-9356
pISSN - 2169-9313
DOI - 10.1029/2019jb017319
Subject(s) - seismology , geology , thrust , thrust fault , fault (geology) , fault plane , nappe , tectonics , engineering , aerospace engineering
The Pamir Frontal Thrust along the leading edge of the northern Pamir is characterized by multiple earthquakes with moment magnitudes of 6.5–7.1. Geometric characteristics of the Pamir Frontal Thrust corresponding to these earthquakes and to future seismic hazards, however, remain largely unexplored. This study focuses on the easternmost segment of the Pamir Frontal Thrust, where the M w 6.9 Wuqia earthquake occurred in 1985. Through interpretation of available two‐dimensional seismic reflection profiles and surface mapping data, we develop a three‐dimensional geometric model for the fault plane. Our results illustrate that, at depth, the fault plane is separated by a subhorizontal detachment horizon into upper and lower ramps, and both ramps are significantly segmented, along strike, by transfer faults or lateral ramps as well. Such along‐strike and downdip segmentation of the thrust sheet apparently plays a significant control on seismic rupture process of the Wuqia earthquake and can well explain why the region is characterized by moderate‐magnitude ( M w 6.5–7.1) events. Additionally, our study helps quantify key constraints on the Cenozoic deformation and evolution of the northeastern Pamir and, specifically, determines a total shortening of ≤43 km at the Pamir front: accommodating about 15% of the total indentation of the Pamir range into central Asia.