利用近期地形变分析地壳应力变化过程的有限单元模拟

FINITE ELEMENT ANALYSIS FOR EARTHQUAKE DEVELOPMENT WITH GROUND

如何把地形变资料与地壳应力联系起来,利用地表所观测到和探测到的地质和地球物理资料来推测分析地下地壳应力变化过程,这是人们正在关注的问题。本文试图利用地形变资料,通过有限单元法来计算地壳的温度分布,进而分析板块边缘地震的机制,为中长期地震预报创造有利条件。

How to relate the geodetic data to the crustal stress is an open question. However, with the annual variation of recent ground deformations between the years 1953-3975, the process of the 1976 Tangshan earthquake development is analyzed thermo-visco-eiastically by quasi-static finite element formulation which has been solved using incremental initiaistrain approach in yearty basis. The deformation rate responsible for isostaic readjustment are regarded as the velocity boundary condition on the free surface, but both the bottom and the ends of the model are constrained by the stiffnes sof their exterior media, and is equivalent to the unknown driving force.Numerical results show that the time-dependent shear stress accumulated in the front of a fault tip due to aseismic creep of same segments along the fault plane playing an important role to generate an earthquake and that the rupture occurring after an accelerated strain rate in the stress-concentrated region has a potential function of helping to identify the localized anomalous deformation rates and is the precursor of an impending earthquake. As for the horizontal compressive force acting on the lateral boundary, when compared with the upper mantle doming seems to be of little impor-tancefor an earthquake development within the marginal basin far away from the plate-boundary.