1976年唐山地震震时和震后变形的模拟

THE SIMULATION OF COSEISMIC AND POSTSEISMIC CRUSTAL DEFORMATION DUE TO TANGSHAN EARTHQUAKE IN 1976

本文采用三维粘弹性有限元方法拟合唐山地区１９７６—１９８５年观测到的地震震时和震后的水平与垂直地形变，反演华北板块下方深部物质的流变学性质．模型采用多层弹性覆盖层与线性粘弹性层的有限块体，发展断层面上存在着位错运动，并用正交设计法拟合观测数据．模拟计算表明，华北板块下方软流层粘度为７．１×１０１８Ｐａ·ｓ；上地幔粘度为２．１×１０１９Ｐａ·ｓ．

In this paper, the observed coseismic and postseismic deformation due to Tangshan earthquake was fitted by inversional computation.Both the horizontal and vertical postseismic deformation fields(1976-1985) after Tangshan earthquake(1976,Ms7.8) are simulated by means of a 3-dimensional finite element method for viscoelastic medium.A model of the deep structure of North China plate with a dislocation on the Tangshan earthquake fault is used. The fault is located in a multilayer elastic medium(lithosphere) lying over a liner viscoelastic layer(asthenosphere),To direct the inversional computation, the orthogonal design method is applied.From the coseismic and postseismic crustal deformation, the inversional computation suggests an asthenospheric viscosity of 7.1×1018Pa·s and a viscosity of 2.1×1019Pa·s for the upper mantle underlying the continental lithosphere.