2008年汶川MW7.9地震库仑应力变化的可靠性研究

Study on the Reliability of Coulomb Stress Change Induced by the 2008 Wenchuan M W7.9 Earthquake

基于2008年汶川M W7.9地震精细的同震滑动分布模型,计算此次地震引起的周边地区库仑应力变化;利用变化系数(CV)评价库仑应力变化的可靠性,并评估接收断层走向、倾角、滑动角、摩擦系数、Skempton系数对库仑应力变化可靠性的影响;根据CV可靠阈值剔除不可靠库仑应力变化,分析可靠库仑应力变化与余震分布之间的关系。结果表明,库仑应力变化在正值区或负值区内部的可靠性较高,在接近正负值交界处库仑应力变化的可靠性急剧下降;接收断层倾角对库仑应力变化可靠性的影响最大;79.3%的余震位于可靠库仑应力变化分布区域,剔除不可靠库仑应力变化及不可靠库仑应力变化分布区域内余震后,余震触发率下降3.1%。

The Coulomb stress change around the source fault induced by the 2008 Wenchuan M W7.9 earthquake is calculated based on the fine coseismic slip distribution model.The reliability of Coulomb stress change and the impact that the strike,dip and rake of receiver fault,the friction coefficient and Skempton coefficient towards the reliability of Coulomb stress change is assessed from the CV(coefficient of variation).The unreliable Coulomb stress change is eliminated according to the threshold value and the relationship between the reliable Coulomb stress change and the distribution of aftershock is analyzed.The results show that the most reliable Coulomb stress change is found inside positive and negative Coulomb stress change area,and the closer to the boundary between positive and negative,the more sharply the reliability decline.Among the parameters analyzed in this paper,the dip angle of receiver fault has the greatest effect on the reliability of Coulomb stress change.79.3%of aftershocks locate in the distribution area of reliable Coulomb stress change and the aftershock triggering rate decreases by 3.1%after excluding the unreliable Coulomb stress change and aftershocks in unreliable area.