震源孕育的数学物理模式与波速异常的理论解释

本文提出了一种震源孕育的数学物理模式,该模式把孕震过程分为扩容,包体形成与发展、流体扩散、失稳四个阶段。用数学物理方法研究了沿断裂带定向的圆柱形孕震区内的孕震过程。通过对这一过程的研究,得出了各孕震阶段持续时间的计算公式。计算结果与波速异常的实际观测结果符合较好。此外,还从理论上研究了确定两相介质中地震波传播速度的问题,给出了P、S波速度与速度比的计算公式,得出了一些定量结果。根据所述结果,对震前地震波速度异常的某些特征(异常持续时间、异常区形状大小及异常幅度)作出了一定的理论解释。最后,用量纲分析和相似理论方法对影响波速异常的一些因素作了简单的讨论。

A PHYSICAL-MATHEMATICAL MODEL FOR THE EARTHQUAKE PREPARATORY PROCESS AND THE THEORETICAL EXPLANATION OF PREMONITORY SEISMIC VELOCITY ANOMALY

In this paper,a physical-mathematical model for the earthquake pre-paratory process is suggested.According to this model,such process inclu-de four stages:dilatation,formation and development of inclusion,fluid diffusin and preseismic instability stages.These stages of the earthquake preparatory process in a cylindrical region along the fault are researched by the method of mathematical physics The computational formula of the duration of every stage is derived from investigqting these subprocesses.The computational results are in agreement with the empirical data of premonitory seismic velocity anomaly.The problem about velocities of seismic waves in the two-phase media is theoretically studied.The computational formulas of the P,S wave vel-ocities and the velocity ratio are given.Some quantitative results are ob-tained.Based on the described results some characteristics of the seismic velo-city anomaly before earthquakes,namely,the duration of anomaly,the form and dimension of anomalous region and the amplitude of anomaly,are theoretically explained.Finally,some factors affecting velocity anomaly are briefly discussed by means of dimensional analysis and analogous theory.