摘要
通过对2003年1月1日—2013年4月1日芦山地震前震源区中小地震震源机制解的分析,发现不同阶段的震源机制解在一定程度上反映了强震孕育过程中构造应力场随时间的变化。震源区中小地震的P轴方位角C_V值在芦山M7.0地震发生前有一个上升-下降-上升的过程,只是相比于汶川8.0级地震前C_V值的下降-上升过程经历了更长的时间,这表明四川芦山M7.0地震的孕育经历了长时间的应力积累,与许多研究结果相一致。2007年1月1日—2014年4月1日C_V值空间分布的非均匀性特征在龙门山断裂带南段有显著的增强与减弱过程,对于发震地点可能有一定的指示意义。
In the preparation process of a strong earthquake,at the potential source area and its vicinity, the tectonic stress field can be enhanced by local tectonic activities.There will be a space-time adj ustment of the stress field with the background of a stable regional stress field.To detect the crustal stress state of the study area,in this paper we analyze the focal mechanism data of small to moderate earthquakes that occurred at the epicenter of the Lushan MS 7 .0 earthquake and its surrounding areas more than ten years before the Lushan earthquake.We obtained the focal mechanism solutions of the small to moderate earth-quakes using the Hardebeck and Shearer （HASH）method,then used the CV value of the P-axis azimuth （the ratio of the standard deviation to its average）to identify the stress field change.The results show that the stress field obviously changed at the seismic source and its surrounding areas with time.The P-axis azimuth CV values of the small to moderate earthquakes exhibited a rise-decline-rise process prior to the Lushan M7 .0 earthquake,which means that there was a long period of stress accumulation before the M7.0 earthquake,consistent with the results of many previous studies.The CV values and apparent stress had the same tendency changes,which obj ectively reflect the changes in the stress field in the process of earthquake preparation.This study demonstrates that there is a certain relationship between the occurrence of strong earthquakes and the change in the P-axis azimuth CV values of small and moderate earthquakes.
出处
《地震工程学报》
CSCD
北大核心
2016年第2期242-248,共7页
China Earthquake Engineering Journal
基金
中国地震局行业专项(201408014)
中国地震局地球物理研究所基本科研重大专项(DQJB11C11)
关键词
震源机制解
P轴方位角
CV
值
focal mechanism solution
P-axis azimuth
CV value
