以克罗地亚M_(S)6.4地震为例检验震前应力集中现象

Examination of Pre-earthquake Stress Concentration Using the Croatian M_(S)6.4 Earthquake Sequence as an Example

为检验大震发生之前是否有应力集中现象,本研究以2020年克罗地亚M_(S)6.4地震及其序列为例,采用比较地震序列的震源机制之间最小空间旋转角的方法来研究应力变化关系。最终发现,主震发生前的一段时间内,该地区发生的不同地震之间的震源机制中心解有趋近主震震源机制中心解的趋势;主震之后,余震的震源机制和主震震源机制之间的差别逐渐增大,并离散开来。此变化趋势一方面是对“应力集中和应变能释放”假说的印证,另一方面则间接说明了该地区的应力分布。由于此次大地震的发生而进行了局部调整,致使局部应力集中趋于平缓,该地区的区域构造板块或许开始进入到下一个应力积累阶段。

To test for stress concentration before a major earthquake,taking the Croatia M_(S)6.4 earthquake as an example,we study the variation of the minimum 3-D rotation angle between the several center of focal mechanisms.We found that the center of focal mechanism between the different earthquakes in this area before the main shock has a tendency to approach the central focal mechanism of the main shock.On the one hand,this trend is a confirmation of the hypothesis of“stress concentration and strain energy release”,on the other hand,it indirectly shows that the stress distribution in this area has been adjusted locally because of the earthquake.The regional tectonic plates in the region may begin to enter the next stage of stress accumulation.