3‐D Numerical Simulation on Influence of 1997 Mani Earthquake to Stability of Tectonic Block System in Qingzang and Chuandian Regions

Abstract

Listen

Translate article

AbstractUsing 3‐D Finite Element Method combined with Discontinuous Deformation Analysis (DDA), in the background of interaction among tectonic blocks in Qingzang and Chuandian, based on the GPS data and seismic focal mechanism, we compute initial displacement field and stress field in the studied region, which agree basically with the results of GPS measurement and seismic focal mechanism distribution. The occurrence process of 1997 Mani earthquake with magnitude Ms 7.9 is simulated numerically, and the features of stress state change on each boundary fault of blocks is studied. (1) The maximum horizontal dislocation is 7 m with left‐lateral and strike; (2) The distribution of dislocation on the seismic fault is similar with the study results of seismic wave; (3) Maximum shear stresses contour is similar with the deformation field characters of D‐INSAR; (4) The vertical displacement distribution computed on the surface across fault indicates that the fault sliding is adverse to north. Distribution of Coulomb failure stress change on the boundary faults of Qingzang and Chuandian block system after Mani earthquake is calculated. Results indicate that the Mani earthquake, except making Coulomb failure stress increase and stress concentration in the ends of the seismic fault, causes Coulomb failure stress increase about 2 MPa at the seismic fault of mid section of eastern Kunlun fracture zone in upper crust layer where Kunlun Shan Ms 8.1 earthquake (H=11 km) occurred in 2001. And it also causes Coulomb failure stress increase about 0.7 MPa at the seismic fault of Kala Kunlun fracture zone in middle crust layer where Gêrzê Ms 6.9 earthquake (H=30 km) occurred in 2008. It seems to indicate that Mani earthquake has great influence on the faults slid of Kunlunshan and Gêrzê earthquakes. The results also indicate that 3‐D DDA+FEM method developed by authors is available to apply in studying relationship between large earthquake occurrence and interaction of tectonic blocks.