基于速率-状态摩擦定律的地震二维准动力学数值模拟:浅层正应力变化对断层演化的影响  

2-D quasi-dynamics numerical simulation of earthquake based on Rate-State Friction law:effect of the variations of shallow normal stress on fault evolution

作　　者：申文豪[1] 薛腾飞[1] 张景发[1] 杨建钦 SHEN WenHao;XUE TengFei;ZHANG JingFa;YANG JianQin(Key Laboratory of Crustal Dynamics,Institute of Crustal Dynamics,China Earthquake Administration,Beijing 100085,China;CNOOC Research Institute,Beijing 100027,China)

机构地区：[1]中国地震局地壳应力研究所(地壳动力学重点实验室),北京100085 [2]中海油研究总院,北京100027

出　　处：《地球物理学报》2018年第8期3198-3210,共13页Chinese Journal of Geophysics

基　　金：国家自然科学基金(41604041);国家自然科学基金(41604040)资助

摘　　要：本文基于结合速率-状态摩擦定律(RSF)的二维准动力学数值模型,以半空间垂直走滑断层为研究对象,通过比较两种正应力随深度变化模型的模拟结果,研究了浅层正应力变化对断层演化参数、地震孕育过程、震后滑移传播等方面的影响.结果显示,我们的数值模型在给定模型参数和约束条件下,能够完整模拟出地震周期中震间、震前、同震以及震后多个特征阶段.常数正应力模型下,动态破裂在浅层速率强化区停止,而在浅层变化正应力模型下动态破裂可以传播至自由表面,导致浅层更高的最大滑移速率和同震滑移量.两种模型下的地震矩、地震周期、平均应力降和震后滑移传播等差别不明显.两种滑移模型的傅氏振幅谱与理论K-2模型傅氏振幅谱均符合较好,且浅层变化正应力模型下的拐角波数值高于常数正应力模型,说明两种模型均符合地震同震滑移模型的运动学特征,并且浅层变化正应力模型下最终应该产生高于常数正应力模型的高频强地面运动水平.我们认为选用不同的模型参数对最终结果存在显著影响,应当根据具体问题来选择模型参数,这样才能在保证结果准确前提下有效提高计算效率.Based on the 2-D quasi-dynamic numerical model combined with Rate-State Friction law,we studied the influence of varying shallow normal stress on fault evolution parameters,nucleation process and postseismic propagation through a two-dimensional vertical strike fault model in half space.Our results show that,under the given model parameters and constraints,our quasi-dynamic numerical model could successfully simulate the characteristics of seismic evolution,including interseismic,preseismic,coseismic and postseismic stage.Under the constant normal stress model,dynamic rupture arrests shortly upon encountering the shallow velocity-strengthening region,while under the depth-dependent normal stress model,dynamic rupture reaches the free surface,leading to higher velocity and coseismic slip.There are no significant differences of earthquake evolution parameters between the above mentioned models,such as seismic moment,earthquake period,the average stress drop and the post earthquake slip propagation speed.The Fourier spectrums of two slip model are in good agreement with the theoretical K-2 model,which reveals that they are consistent with the kinematic characteristics of coseismic slip model.Since the corner wavenumbers of the depth dependent normal stress model are higher than the constant normal stress model,we could expect that it may produce higher high frequency ground motion.We believe that the choice of different model parameters has a significant impact on final results,and appropriate model parameters should be selected according to specific problems,so as to ensure accurate results and improve the calculation efficiency.

关 键 词：速率-状态摩擦定律 准动力学数值模拟 断层演化 地震参数 

分 类 号：P315[天文地球—地震学]