Earthquake monitoring and high-resolution velocity tomography for the central Longmenshan fault zone by a temporary dense seismic array  

作　　者：ShaoBo Yang HaiJiang Zhang MaoMao Wang Ji Gao Shuaijun Wang BaoJin Liu XiWei Xu 

机构地区：[1]School of Carbon Neutrality Science and Engineering,Anhui University of Science and Technology,Hefei 231131,China [2]Laboratory of Seismology and Physics of Earth’s Interior,School of Earth and Space Sciences,University of Science and Technology of China,Hefei 230026,China [3]Mengcheng National Geophysical Observatory,University of Science and Technology of China,Hefei 230026,China [4]Institute of Tectonics and Geophysics,College of Oceanography,Hohai University,Nanjing 210098,China [5]Geophysical Exploration Center,China Earthquake Administration,Zhengzhou 450002,China [6]School of Earth Sciences and Resources,China University of Geosciences,Beijing 100083,China

出　　处：《Earth and Planetary Physics》2025年第2期239-252,共14页地球与行星物理(英文版)

基　　金：supported by the Scientific Research Foundation for High-level Talents of Anhui University of Science and Technology under Grant 2024yjrc64;the National Key R&D Program of China under Grant 2018YFC1504102。

摘　　要：The Longmenshan(LMS) fault zone is located at the junction of the eastern Tibetan Plateau and the Sichuan Basin and is of great significance for studying regional tectonics and earthquake hazards. Although regional velocity models are available for the LMS fault zone, high-resolution velocity models are lacking. Therefore, a dense array of 240 short-period seismometers was deployed around the central segment of the LMS fault zone for approximately 30 days to monitor earthquakes and characterize fine structures of the fault zone. Considering the large quantity of observed seismic data, the data processing workflow consisted of deep learning-based automatic earthquake detection, phase arrival picking, and association. Compared with the earthquake catalog released by the China Earthquake Administration, many more earthquakes were detected by the dense array. Double-difference seismic tomography was adopted to determine V_(p), V_(s), and V_(p)/V_(s) models as well as earthquake locations. The checkerboard test showed that the velocity models have spatial resolutions of approximately 5 km in the horizontal directions and 2 km at depth. To the west of the Yingxiu–Beichuan Fault(YBF), the Precambrian Pengguan complex, where most of earthquakes occurred, is characterized by high velocity and low V_(p)/V_(s) values. In comparison, to the east of the YBF, the Upper Paleozoic to Jurassic sediments, where few earthquakes occurred, show low velocity and high V_(p)/V_(s) values. Our results suggest that the earthquake activity in the LMS fault zone is controlled by the strength of the rock compositions. When the high-resolution velocity models were combined with the relocated earthquakes, we were also able to delineate the fault geometry for different faults in the LMS fault zone.

关 键 词：Longmenshan fault zone dense seismic array deep learning double-difference seismic tomography seismic velocity model earthquake locations fault geometry 

分 类 号：P315.7[天文地球—地震学]