In this paper we use three-dimensional spherical shell finite element model of power-law creep mechanism, to analyze the stress field variation in china mainland caused by the brittle failure of Longmenshan fault, during 5.12 Wenchuan earthquake. We establish a local coordinate system and the maximum shear failure criterion on the fault zone, and simulate the earthquake brittle rupture by decreasing shear modulus. After Wenchuan earthquake, the crustal stress field shows that:
In the middle and the northern section of Longmen mountain central fault zone, the shallow maximum principal stress value has a larger decline; the amount of decline decreases with increasing distance from the fault zone. The decline of differential stress is more obvious, which also decreases with increasing distance from the fault. The calculated change trend of the maximum horizontal principal stress is consistent with the actually measured stress change after the earthquake.
Stress in the south section of Longmen Mountain is still higher than that in other areas of the fault zone, and the southern section of the fault is still under high stress accumulation.
The overall orientation of maximum principal stress is consistent on fault zone. The direction of maximum horizontal principal stress rotated clockwise during the earthquake, which is 290° in the depth of 2000 m near the focus as compared with 280° before the earthquake, the rotation angle is about 10°.
The Wenchuan Ms8.0 earthquake occurred in the Longmen Mountain Fault Zone on May 12, 2008. The earthquake lasted 90s, the length of the rupture zone was about 300km, and the average slip on the whole fault plane reached 2.4m, the maximum was 7.3m. The tremendous energy released by the earthquake triggered a series of geological disasters, resulting in huge economic losses and casualties.
