前震序列的图像特征研究

Pattern characteristics of foreshock sequences

地震丛集在时间和空间上分布具有不同的特征,2个特殊的例子就是前震序列和震群。基于对1966~1996年中国大陆8个前震序列的分析,本研究提取了如下前震序列的图像特征：①前震序列的震中在空间上密集集中;②前震的震源机制与主震的震源机制相似,而这种与主震震源机制的一致性在余震序列和震群中并不存在;③这30年在中国大陆我们尚未发现主震之前的前震丛集的震源机制不一致。最后,我们发现中国大陆5%的主震前发生前震序列。

Earthquake clusterings in both space and time have various forms. Two typical examples are the foreshock sequences and earthquake swarms. Based on the analysis of 8foreshock sequences in Chinese mainland during 1966 ~ 1996,this study concentrates on the pattern characteristics of foreshock sequences. The following pattern characteristics of foreshock sequences have been found：（ 1） The epicenters of foreshock sequences were densely concentrated in space.（ 2） The focal mechanisms of foreshocks were similar to that of the main shock. Such consistency of focal mechanisms with main shocks did not exist in aftershock series as well as in several earthquake swarms.（ 3） We found no case in Chinese mainland during the past30 years that a main shock was preceded by an earthquake clustering with inconsistent focal mechanisms. Finally,we found 5% of the main shocks in Chinese mainland were preceded by foreshock sequences.