Dynamic changes of gravity field before the Luding Ms6.8 earthquake and its crustal material migration characteristics  

作　　者：Qingqing Tan Chongyang Shen Jjiapei Wang Xiong Yang Wen Jin Minghui Zhang Hongbo Tan Guangliang Yang 

机构地区：[1]Key Laboratory of Earthquake Gedesy,Institute of Seimogy.China Earthquake Adminitration,Wuhan 43071,China [2]Gravitation and Earth Tide,National Observation and Research Station,Wuhan 430071,China [3]The Second Monitoring and Application Center,China Earthquake Administration,Xi'an 710054,China [4]Hunan Earthquake Agency,Changsha 410004,China

出　　处：《Geodesy and Geodynamics》2025年第2期214-222,共9页大地测量与地球动力学(英文版)

基　　金：the National Natural Science Foundation of China(Grant No.42374105,42204089,42174104);Scientific Research Fund of Institute of Seismology,China Earthquake Administration(Grant No.IS202326341,IS202336350).

摘　　要：On September 5,2022,an earthquake of magnitude Ms6.8 occurred in Luding County,Sichuan Province.This earthquake occurred at the key part of the southeast-clockwise extrusion of material on the eastern margin of the Qinghai Plateau,the Y-shaped confluence of the Xianshuihe,Longmenshan and Anninghe fault zones.In this study,the three-dimensional dynamic crustal density changes in the earthquake area are obtained by the typical gravity change data from 2019 to 2022 before the earthquake and gravity inversion by growing bodies.The results indicate that gravity changes presented an obvious fourquadrant and gradient belt distribution in the Luding area before the earthquake.The threedimensional density horizontal slices show that small density changes occured at the epicenter in the mid-to-upper crust between 2019.9-2020.9 and 2019.9-2021.9.At the same time,the surrounding areas exhibited a positive and negative quadrant distribution.These observations indicate that the source region was likely in a stable locked state,with locking-in shear forces oriented in the NW and NE directions.From 2021.9 to 2022.8,the epicentral region showed negative density changes,indicating that the source region was in the expansion stage,approaching a near-seismic state.The three-dimensional density vertical slices reveal a southeastward migration of positive and negative densities near the epicenter and on the western of the Xianshuihe Fault Zone,indicating that the material is flowing out to the southeast.The observed local negative density changes at the epicenter along the Longmenshan Fault Zone are likely associated with the NE-oriented extensional stress shown by the seismic source mechanism.The above results can provide a basis for interpreting pre-earthquake gravity and density changes,thereby contributing to the advancement of earthquake precursor theory.

关 键 词：Luding earthquake Gravity changes Three-dimensional density changes Gravity inversion 

分 类 号：P315.7[天文地球—地震学]