地震孕育发生的场源关系初步研究

Preliminary Research on the Relations Between Field and Source in Earthquake Preparation

场和源在地震学和地震预报研究中已成为两个最重要分支。本文应用计算机模型研究地震活动中的场源关系。模型中以非线性元件构成的网络系统来模拟含有多个地震活动带的地震构造块体的地震活动。在模型边界上加以定常应变速率,则在模型中可产生高低起伏的轮回式地震活动,并形成应力场强度和应变能高低起伏的准周期变化;各地震活动轮回有其主体活动地区,不同的轮回之间常显示出地震主体活动区的空间转移。同时,若将模型中达到一定高应力值的元件看成前兆异常区,则模型中的前兆异常呈现复杂的特征,异常与地震并无一一对应;在地震活动相对平静时期和相对活跃时期,整个模型中前兆显示有较大差别;在强震活动高潮阶段,构造块体各地震带(包括未参与强震活动的地震带)都有应力增强的过程。上述的诸方面结果对认识孕震过程和地震活动的场源关系有重要的启示。

The 'field' and the 'source' are the two important branches in seismology and earthquake prediction researches. In this paper, we use a computer model to study the relations between the field and the source in earthquake activities. In our modeling,a network of nonlinear elements is used to simulate seismic activities of seismic zones in a seismic tectonic block. Constant strain rate is enforced on the boundary of the model, cyclic seismic activities and quasi-periodic variations of stress field intensity and strain energy are observed with high and low fluctuations. There exists the mian seismicity area in seismic cycles,and the main seismicity area migrates in space during different seismic cycles. If precursory area is related to high element stress, the development of precursors in our model is found quite complicated. No unique relations between precursors and earthquakes are discovered. Anomalies show different characteristics in the seismic quiet period and active period. All of the seismic belts in the system have been under a state of stress build-up in the seismic active period,although in some of them no large events occurred. The results concluded above provide a better insight to the field and the source relations in earthquake preparatory process and activity.