四川长宁6.0级地震库仑应力变化及其对余震的触发作用

The Coulomb Stress Change of the Sichuan Changning 6.0 Earthquake and Its Triggering Effect on Aftershocks

2019年6月17日四川长宁发生6.0级地震,截至8月20日总共记录到3级以上余震64次。此次地震发生在一条北西向的隐伏断层。为分析区域地震危险性,综合考虑同震位错和震后粘滞松弛效应,利用PSGRN/PSCMP程序计算地震破裂面上产生的库仑应力变化,分析长宁6.0级地震的长时间尺度库仑应力演化特征及其对3级以上余震的触发作用。结果表明3级以上余震发生在应力触发区概率达到96.9%。同时计算Burgers粘弹性模型的长时间尺度库仑应力动态变化。结果显示应力触发区主要分布在震区的北北西、南南东、北东东和南西西向,将库仑应力动态演化特征应用到本区地震危险性分析时,重点关注上述应力触发区,为后续余震发生提供地点依据。

On June 17^th,2019,an MS6.0 earthquake occurred in Changning,Sichuan Province.64 aftershocks with M≥3 were recorded until August 20^th.The earthquake occurred on a buried fault in the northwest direction.To analyze the regional seismic hazard,this paper comprehensively considers the co-seismic dislocation and post-earthquake viscous relaxation effects,uses the PSGRN/PSCMP program to calculate the Coulomb stress change generated on the earthquake rupture surface,and analyzes the long-time scale Coulomb stress evolution characteristics of the Changning M6.0 earthquake and its triggering effect on aftershocks with M≥3.The results show that the probability of aftershocks with M≥3 occurring in the stress triggering zone reaches 96.9%.At the same time,the paper calculates the long-term dynamic Coulomb stress change by using Burgers viscoelastic model.It shows that the stress triggering areas are mainly distributed in the north-north-west,south-south east,northeast and south-west directions of the earthquake area.The paper applies the dynamic evolution characteristics of Coulomb stress to the seismic hazard analysis of this area,and focus on the above-mentioned stress triggering area to provide a location basis for subsequent aftershocks.