汶川8.0和芦山7.0级地震序列应力场时空特征  

SPATIAL AND TEMPORAL CHARACTERISTIC OF STRESS FIELD FOR WENCHUAN M_S8.0 AND LUSHAN M_S7.0 EARTHQUAKE SEQUENCE

作　　者：张致伟[1] 周龙泉[2] 龙锋[1] 阮祥[1] 

机构地区：[1]四川省地震局,成都610041 [2]中国地震台网中心,北京100045

出　　处：《地震地质》2015年第3期804-817,共14页Seismology and Geology

基　　金：中国地震局地震科技星火计划项目(XH14045Y);中国地震局青年震情跟踪课题(2014020102)共同资助

摘　　要：分别基于汶川M≥4.0和芦山M≥3.0余震震源机制解,采用Michael提出的应力场反演方法,分析了汶川、芦山余震区压应力(S1)和应力张量方差的空间分布特征,研究了应力张量方差时空变化与强余震活动的关系。结果表明:1)汶川、芦山余震区S1方位复杂,存在显著的空间分区差异,主震起始破裂区附近S1方位相对紊乱,应力张量方差明显偏高;2)汶川余震区自西南至东北,S1方位由近EW向逐渐转变为NW-SE向,最后在余震区的北段又转为近EW向,应力类型均呈逆断型,而理县分支S1方位呈NEE向,应力类型为走滑型,整个余震区S1呈近水平特征;3)芦山余震区S1方位总体呈现NW向,倾角近水平,除主震震中附近的应力类型为纯逆断型外,其他区域走滑型和逆断型的应力类型均有存在;4)应力张量方差时空分布对于强余震的发生具有一定的指示意义,汶川、芦山强余震均发生在应力张量方差低值分布区或其边缘附近,且汶川强余震的发震时间也在其出现低值的时段。Based on focal mechanism solutions of Wenchuan M ≥ 4. 0 and Lushan M ≥ 3. 0 aftershocks,using inversion method of stress field to analyze the spatial distribution characteristic of compressive stress（ S1） and stress tensor variance of Wenchuan and Lushan aftershock zones,the relation between spatial and temporal distribution of stress tensor variance and strong aftershock activity are studied.The results show that（ 1） The orientations of compressive stress（ S1） are complex in Wenchuan and Lushan aftershock zones,there exists obvious regional difference spatially,the S1 orientations all present disorder feature near the main shock rupture zone,and the stress tensor variances are obviously higher.（ 2） Along Wenchuan aftershock zone from southwest to northeast,the compressive stress orientation gradually changes from EW to NW- SE,finally,it presents near EW direction at north segment of aftershock zone,and the stress type is all thrust; the S1 orientation presents NEE direction in Lixian branch of Wenchuan aftershock zone,the stress type shows strike-slip type,the compressive stress presents a near horizontal feature in whole aftershock zone.（ 3） The compressive stress orientation presents NW direction in Lushan aftershock zone,the dip angle is near horizontal,the stress type is thrust near the main shock and strike-slip and thrust in other areas.（ 4） The spatial and temporal distribution of stress tensor variance has certain indicative significance for occurrence of strong aftershock,most later-phase strong aftershocks of Wenchuan and Lushan earthquake occurred in the low-value area of stress tensor variance and its fringe areas,the origin time of Wenchaun strong aftershocks are also at the time frame of low value of stress tensor variance.

关 键 词：汶川地震 芦山地震 震源机制 压应力 应力张量方差 

分 类 号：P315.727[天文地球—地震学]