相互作用断层失稳的前兆变化的分析

ANAIYSIS FOR PRECURSOR CHANGE OF INSTABILITY ON INTERACTIVE FAULTS

本文从理论上研究贯通地壳的两条相互平行的具有滑动—弱化型本构律的断层的相互作用。采用有限单元—松驰迭代方法,分别对走滑断层,正断层和逆断层三种不同情况的断层相互作用问题进行了模型计算,并对位移场、应力场、应变场以及弹性应变能随时间的变化进行了数值分析。结果表明,在所讨论的几种情况下,两条相互作用的断层相继发生失稳,从动态角度反映出断层的相互作用。断层失稳前,在不同区域有截然不同的前兆变化,而同一区域对不同断层失稳的前兆响应也不相同,有些区域为“前兆灵敏点”,而有些地方则为“前兆盲点”。这些结果对于研究合理的观测条件和最佳观测布局有一定的理论意义,对于分析大震的前兆异常也有所裨益。

In this paper, the interaction of two parallel faults which penetrate crust has been studied theoretically. It has been assumed that the faults satisfy a slip-weakening constitutive low, but the peak strengthes are different. We have calculated the interactions for strike, normal and reverse faults respectivly, and numerically analysed the cha- nges in displacement, stress, strain fields and elastic strain energy by means of finite element and slack iteration method. The results show that instability sequentially occurs for interaction on two faults, which reflect the interaction of two faults in the form of dynamics. Before the fault instability, the precursor changes in variant zone a- re completely different. And for variant fault instability, the precursor changes in the same zone are different, too. Some zones are 'sensitive point' for precursor, aud some zones are 'blind point'.