摘要
为研究2013年4月20日芦山Mw6.6地震的发震构造及孕震机理,基于4月20日—6月1日地震序列中114次M≥3.0余震震源机制解,深入分析了余震震源机制及震源区应力场的时空分布特征,获得的主要认识如下：（1）芦山M≥3.0余震以逆冲型为主,走滑型次之,正断型最少,震源机制P轴方位一致性较好,以近NWW-SEE为优势方向,倾角分布在0～30°,表明余震活动主要受龙门山断裂所在的区域应力场控制;（2）芦山余震区压应力S1方位存在明显的局部空间分区差异,以主震震中为界,余震区南边S1方向总体呈NWW方向,而余震区北边S1方向表现出由NW经EW向NE的逆时针旋转,可能反映了余震区北边发震断层错动以逆冲为主兼有一定的走滑分量;（3）压应力S1方位随时间的变化不明显,呈近NWW方向,但其倾角逐渐变水平,应力张量方差逐渐变大,震源机制错动类型始终以逆冲为主,随时间变的相对紊乱,反映了震源区应力场随时间的调整变化特性;（4）深度剖面结果显示压应力方位与发震断层走向的夹角在80°～120°,即近乎垂直,震源断层面向NW倾斜,芦山余震活动受控于近垂直发震断裂的挤压作用,属于典型的逆冲断层。
In order to investigate seismogenic structure and seismic mechanism of I.ushan Mw6.6 earthquake on 20 April 2013, based on focal mechanism solutions of 114 M≥3.0 aftershocks from 20 April to 1 June 2013, we analyzed spatial and temporal distribution characteristic of focal mechanism and stress field. The results are as follows. （ 1 ） The focal mechanism types of Lushan M≥3.0 aftershocks show that thrust type is dominant faulting behavior, strike-slip type takes second place, normal type is least, the orientation of P-axis have a good consistency, the dominant direction is near NWW SEE, dip angle is from 0° to 30°, it shows that aftershock activities are controlled by regional stress field. （2） The orientations of compressive stress （S1） exists obvious space partition difference in Lushan aftershock zone, the epicenter of main shock as boundary, the S1 orientation presents NWW in the south of aftershock zone, and it is anticlockwise rotation from NW to NE in the north of aftershock zone. The dislocation type of causative fault in the north of aftershock zone is mainly characterized by thrust with the component of strike-slip. （3） The change of S1 orientation with time is not obvious, it presents near NWW direction, but its dip angle gradu- ally becomes level, stress tensor variance gradually becomes big, and the focal mechanism is mainly thrust behavior all the time, but it becomes relatively untidy with time, it reflects that seismic source stress field continually adjusts with time. （4） The depth profiles show that angle between S1 direction and causative fault strike is 80°- 120° in most area, it is almost per pendicular to fault strike, the trend of focal fault plane is NW, it shows that Lushan earthquake sequence is controlled by near level compressive stress which is perpendicular to causative fault, it belongs to typical thrust fault.
出处
《地球科学（中国地质大学学报）》
EI
CAS
CSCD
北大核心
2015年第10期1710-1722,共13页
Earth Science-Journal of China University of Geosciences
基金
地震科技星火计划项目(No.XH14045Y)
中国地震局监测预报司震情跟踪青年课题(No.2014020102)
关键词
芦山地震
震源机制解
压应力
应力张量方差
天然地震
Lushan earthquake
focal mechanism solution
compressive stress
stress tensor variance
earthquakes
