A Possible Mechanism of Crustal Deformation Before the Xingtai Earthquake in 1966

Abstract

The medium of crust model is treated as Maxwell medium, and the model includes hard inclusion, soft inclusion, and deep-seated fault. By using three-dimensional finite element method and differential method, the change of disturbed average stress and disturbed maximum shear stress with time and the crustal deformation on the surface of the model is calculated. (1) At the depth of 11 km in crust, the change of disturbed maximum shear stress caused by the speedup creep of the deep-seated fault is accelerated by hundreds of times. The beginning of the deep-seated fault instability is the beginning of forming the core of the Xingtai large earthquake in 1966. This character is very favorable to quickly transfer shear strain energy from the lower crust to the upper and middle crust. (2)The character of deformation on the surface of the model is very similar to that in Xingtai area before large earthquake in 1966. We may conclude that the precursor is connected not only with the dilation of rock but also with the creep instability along the deep-seated fault before large earthquake.