基于分裂节点法的地震同震和震后形变数值模拟及其在汶川大地震中的应用  

Numerical simulation of coseismic and postseismic deformation through a node-splitting algorithm:A case study of the Wenchuan earthquake

作　　者：孙云强 罗纲 黄禄渊 SUN Yunqiang;LUO Gang;HUANG Luyuan(College of Transportation and Civil Engineering,Fujian Agriculture and Forestry University,Fuzhou 350002,Fujian,China;School of Geodesy and Geomatics,Wuhan University,Wuhan 430079,Hubei,China;National Institute of Natural Hazards,MEMC,Beijing 100085,China)

机构地区：[1]福建农林大学交通与土木工程学院,福建福州350002 [2]武汉大学测绘学院,湖北武汉430079 [3]应急管理部国家自然灾害防治研究院,北京100085

出　　处：《地质力学学报》2021年第2期241-253,共13页Journal of Geomechanics

基　　金：国家自然科学基金(41974107,41590865,U1839207);中国地震科学实验场专项(2019CSES0112);福建农林大学青年教师科研基金(71201800208)。

摘　　要：大地震导致的同震及震后效应,对于分析不同地震之间的相互影响及区域地震危险性等有着重要的作用。文中开发了模拟地震同震及震后效应的三维黏弹性有限元程序,通过计算走滑断层震例(概念性模型)引起的同震及震后效应,并与解析/半解析解进行对比,验证了程序的可靠性。同时基于概念性模型,分析了不同介质参数对同震及震后的地表变形的影响。研究表明,地球介质的横向不均匀性对地震同震位移有显著的影响,而中下地壳上地幔的黏度对震后效应起着主要控制作用。最后将该程序应用于青藏高原东缘,计算分析了2008年M_(W)7.9汶川大地震导致的同震及震后库仑应力变化对2013年M_(W)6.6芦山地震及2017年M_(W)6.5九寨沟地震的影响。结果显示,汶川地震导致的库仑应力变化在芦山地震震源附近(0.013 MPa)及九寨沟地震震源附近(0.009 MPa)都为正值,说明汶川地震可能使得两次地震提前发生。The coseismic and postseismic effects are crucial elements in analyzing fault interactions and the regional seismic risk.In this paper,we developed a three-dimensional viscoelastic finite element code to simulate the coseismic and postseismic deformation.We calculated the coseismic and postseismic deformations caused by the strike-slip fault with a conceptual model,and compared the results with the analytic and semi-analytic solutions so as to verify the reliability of the code.Meanwhile,we also analyzed the influence of different parameters on the coseismic and postseismic deformation,uncovering a significant effect of the earth’s lateral heterogeneity on the coseismic displacement.And the viscosity of the middle-lower crust and upper mantle plays a major role in controlling the postseismic displacement.At last,we used the three-dimensional viscoelastic model to calculate the changes of the coseismic and postseismic Coulomb stress caused by the 2008 M_(W)7.9 Wenchuan earthquake,and analyzed the subsequent effect on the 2013 M_(W)6.6 Lushan earthquake and the 2017 M_(W)6.5 Jiuzhaigou earthquake.The calculation results show that the Coulomb stress changes caused by the Wenchuan earthquake is positive near the hypocenters of the Lushan earthquake(0.013 MPa)and the Jiuzhaigou earthquake(0.009 MPa),indicating the Wenchuan earthquake might have triggered both the Lushan earthquake and Jiuzhaigou earthquake.

关 键 词：地震位错 震后形变 三维黏弹性 库仑应力 汶川地震 

分 类 号：P315.5[天文地球—地震学]