摘要
在构造应力场的制约下强震孕育过程中特定阶段,震源区中小地震震源机制与构造应力场的方向大体一致,根据这一特点,定义各个震源机制解的P轴,B轴,T轴和构造应力场的3个应力主轴在3维空间的夹角之和为一致性参数a,研究强震前应力场变化特征。对2006年11月15日千岛岛弧MW8.3地震和2001年6月23日秘鲁MW8.4地震研究表明,大震发生前孕震区一致性参数a比较低,震源机制与构造应力场的差异较小,说明这些前震受到了震源区应力场的统一作用,而主震发生之后震源机制解的一致性参数比较高,说明后续发生的地震的震源机制散乱,表明背景应力场的控制作用开始减弱。
At some stage of earthquake preparation, the focal mechanisms of small and medium-sized earthquake have roughly the same direction with the tectonic stress field. According to this feature, we define the angle between P, B, and T axises of focal mechanisms and three stress axises of tectonic stress field as the consistency parameter a, to research the dynamic changes of stress field in earthquake preparation area before strong earthquakes. In this paper, we mainly studied the changes of the consistency parameter a of the Kuril island are Mw8.3 earthquake and Peru Mw8.4 earthquake. Our study found that before strong earthquake occurred, the focal mechanisms of a series of small and medium-sized earthquakes get small differences with the tectonic stress field, this indicates that those foreshocks are under the control of stress field, the focal mechanisms of shocks occurred at this time have the same direction with tectonic stress field; while the higher consistency means that the focal mechanisms of aftershoeks are scattered, and have big difference with tectonic field, which means the control of background stress field start weakening.
出处
《地震》
CSCD
北大核心
2010年第1期108-114,共7页
Earthquake
基金
中国地震局地震预测研究所基本科研业务(0207690205)资助
关键词
震源机制
一致性参数
千岛岛弧
秘鲁
Focal mechanism
Consistency parameter
Stress field
Kuril island
Peru
