关键词: 龙门山断层, 地表变形, 有限元, 位错模型

Abstract: This paper mainly studies the distribution of structural deformation and stress under the motion of thrust fault due to the effect of stress normal to the strike direction. As an example,we build the finite element model of central fault of Longmen Shan Fault zone,the Yingxiu-Qingchuan Fault. The finite element model is the model of single inverse fault. During the study,we compute the variations of surface deformation and stress fields near to the fault due to the thrust motion of Yingxiu-Qingchuan Fault in the process of Wenchuan earthquake. In the computation,we apply the frictional contact element and curved surface geometry to simulating the fault plane to obtain the variations of stress components and displacement field which are normal to strike direction and ground surface. In order to get the stress value of the hanging fall of the Yingxiu-Qingchuan Fault,we also apply the static dislocation model to the computation. Through the computation,we find that the displacement field along the strike direction can exist even if there is no initial stress load along the strike,but the value of this deformation is tiny. So we believe the displacement field along the strike may stem from the transverse deformation due to the extrusion of thrust fault; The structure deformation normal to the strike direction resulting from the thrust motion of inverse fault does not reach to maximum value at the zone near the fault,but the structure deformation normal to the ground surface can reach the maximum at the zone near to the fault; Generally,under the compression stress effect,the amount of crustal shortening is much bigger than that of uplift deformation at the zone near to the inverse fault,and the value of compression stress is much bigger than that of stress normal to ground surface along the fault plane. Furthermore,variation of stress on the inverse fault plane occurs mainly at the area where the dip angle of fault plane changes.

Key words: Longmenshan Fault, surface deformation, finite element method, dislocation model