日本M_W9.0级地震同震位移场和应力场的有限元模拟

Modeling of the Co-seismic Displacement Field and Stress Field of M_w9.0 Earthquake in Japan by Finite Element Method

根据同震位移GPS观测数据,利用有限元法反演了2011年3月11日本MW9.0级地震的断层滑移模式。在此基础上,计算了日本MW9.0级地震引起的同震位移场和应力场,给出了位移和应力的分布,分析了他们的变化规律并与实测结果进行了对比。计算结果表明:日本MW9.0级地震的静态断层滑移量最大可达25 m。地震引起断层上盘向东位移,最大位移在震中附近,可达24.25 m,日本东北地区向东位移最大可达6 m。震后地表隆起,隆起幅度可达5.6 m,隆起的最高点也在震中附近。日本东北地区东海岸附近有一下沉带,下沉量可达0.8 m。同震地表位移的计算值与GPS测量结果基本一致。地震引起应力变化,导致震后应力下降。应力变化是不均匀的,在震中附近约为9.9 MPa,在深处可达32 MPa,在日本东北地区地表应力变化小于4.4 MPa。地震引起的应力变化主要是水平应力,垂直应力基本不变。

According to the GPS data, the fault-slip model for Mw9.0 earthquake in March 2011 was inversed by using the finite element method. On the basis of the inversion, co-seismic displacement and stress fields were calculated, and the distribution of displacement and stress was given. The results show that fault-slip was up to 25 m. Northeast Japan was moved eastward by 1-6 meters, and the maximum displacement in the epicentral area was up to 24.25 m. After the earthquake, the surface was uplifted by about 5.6 meters near the epicenter. There was a depression area of 0.8 meters in the east coast of Northeast Japan. The calculated co-seismic surface displacement is consistent with GPS measurements. Stress was changed by the earthquake, resulting in the decrease of the post-earthquake stress. Stress change was about 9.9 MPa near the epicenter, 32 MPa in the depths, and less than 4.4 MPa in Northeast Japan. Earthquake-induced stress changes were mainly horizontal stress, whereas vertical stress changes were very small.