地震活动的简化模型研究

A SIMPLIFIED MODELING OF SEISMICITY

大陆地震活动带的地震活动表现为平静和活跃相交替的轮回活动特征,各轮回中强震活动呈现出时间和空间上的迁移特征。为了探索这种活动特征的机制,本文试图用数值模型来探讨在统一构造应力场作用下的地震活动带的地震活动特征。模拟中的事件表现出类似于实际地震活动的一些特征,例如震级—频度关系和地震平静—活跃的交替特征等。如果把模型中元件上接近破裂强度的高应力值与前兆加以联系的话,我们发现模型中的前兆变化具有复杂性。模型中大事件的前兆并不是集中在未来大震的周围,而是在整个系统中大范围内出现。系统中前兆出现的程度与地震大小之间没有确定的对应关系。统计表明从前兆出现的范围只能估计出未来发生地震的上限值。

Seismic active and quiescent episodes are found in continental seismic zones of China and intense activities of adjacent seismic zones show correlation in time and migration from one zone to another one in space. The mechanism of the activity characteristics is not well understood. In this paper, we use nonlinear dynamic models to simulate the seismic activity in fault zones under a unified tectonic stress field. Events produced in the modeling show remarkable similarity to realistic seismicity, such as the power law frequency-magnitude relation and the active-quiescence episodes If precursors are correlated to high element stress close o its strength, the complicated development of precursors before large events is found. Precursors for large events are not limited to elements surrounding the forthcoming large event, in contrary, precursors occur widely in the whole system. According to the intensity of precursors, the maximum magnitude of event which might occur in the system can be estimated, but no definite relation is found between the magnitude of events and the intensky of precursors.