A study on the rupture process of the 2001 M_s8.1 Kunlunshan earthquake and its influence on pregnant process and occurrence of the M_s8.0 Wenchuan earthquake in 2008

In this paper,3D Finite Element Method combined with Discontinuous Deformation Analysis is used to firstly calculate velocity and stress fields of the Qingzang Plateau in the framework of northward compression of the Indian Plate and obstruction of the strong crust of Sichuan basin,with constraints from GPS data and focal mechanism.Then we simulated the rupture process of the Kunlunshan M_S8.1 earthquake in 2001,and studied the characteristics of stress change on the boundary faults of tectonic blocks caused by the earthquake,especially the influence on the seismogenic fault of the Wenchuan earthquake in 2008.The results show that (1)the Kunlunshan earthquake undergoes sinistral strike-slip movement,the calculated maximum horizontal dislocation of the seismogenic fault is 4.5 m,and the calculated maximum stress drop is 18 MPa.The distribution of principal compressive stress change,the contour map of maximum shear stress change before and after Kunlunshan earthquake,the 3D distribution of the vertical displacement caused by the earthquake acquired via calculation are totally in agreement with the focal mechanism solution,the coseismic displacement distribution on the rupture zone of the earthquake.(2)The maximum shear stress variation on the north and south sides of the seismogenic fault is asymmetrical,with the stress change gradient on the south side much greater than that on the north side.(3)We find that the Kunlunshan earthquake caused the Coulomb failure stress increase 0.016 MPa(upper crust)on the seismogenic fault of the 2008 Wenchuan earthquake.The rupture process of Kunlunshan earthquake,a sinistral strike-slip movement on the seismic fault of eastern Kunlun fracture zone,caused Bayankala block at southern side of eastern Kunlun fracture zone to extend further to east and deform to a certain extent.Meanwhile,the obstruction of stronger crust in Sichuan basin at eastern side of Bayankala block made the Coulomb failure stress increase and strain energy accumulation strengthen,on seismic fault of Wenchuan earthquake with low dip angle at eastern boundary of the block.Therefore,the occurrence of the Kunlunshan earthquake has played a role of promoting the generation and instability of the seismogenic fault of the Wenchuan earthquake.