巧家地震和鲁甸地震震源区周边P波速度结构  

Three-dimensional P-wave velocity structure around the sources of Ludian and Qiaojia earthquakes

作　　者：王长在[1] 吴建平[1] 刘雅宁 杨婷[1] 范莉苹 刘靖 Wang Changzai;Wu Jianping;Liu Yaning;Yang Ting;Fan Liping;Liu Jing(Institute of Geophysics,China Earthquake Administration,Beijing 100081,China)

机构地区：[1]中国地震局地球物理研究所,中国北京100081

出　　处：《地震学报》2021年第1期1-12,共12页Acta Seismologica Sinica

基　　金：国家重点研发计划(2017YFC0404901);国家自然科学基金(41704064,41774067)联合资助。

摘　　要：本文利用2010年1月至2020年6月巧家地震和鲁甸地震震源区周围发生地震事件的走时观测资料,应用双差层析成像方法获得了2014年MS6.5鲁甸地震和2020年5月18日巧家MS5.0地震周边区域中上地壳的P波速度结构。成像结果显示:整个研究区域的速度结构存在很强的非均匀性:在鲁甸地震震源区附近,浅部存在速度高达6.4 km/s的显著高速异常,10 km深度以下存在速度低至约5.8 km/s的明显低速异常;鲁甸地震的初始破裂点位于高低速异常的过渡带;在2010年巧家MS4.8和2020年巧家MS5.0地震的震源区,尽管浅部没有显著的高速异常,但在主震的初始破裂点下方均存在明显的局部低速异常;巧家北部中上地壳存在明显低速异常。Using travel times of earthquakes from January 2010 to June 2020 in the region of Qiaojia and Ludian,we obtained three-dimensional P-wave seismic velocity structures around the source areas of Qiaojia and Ludian earthquakes by double-difference tomography. The result show that the velocity structure in this area is strongly heterogeneous,which affects the distribution of active faults. In the source region of the Ludian earthquake,there is a significant P wave high velocity anomaly with a maximum velocity up to 6.4 km/s,and an obvious P wave low velocity anomaly with a minimum velocity of about 5.8 km/s below the depth of 10 km.The occurrence of Ludian earthquake may be related to the difference of mechanical properties between deep and shallow rocks and the presence of fluid in mid-upper crustal rocks. In the source areas of the 2010 Qiaojia MS4.8 earthquake and the 2020 Qiaojia MS5.0 earthquake,although there are no significant high-velocity anomalies in the shallow crust,there are obvious local low-velocity anomalies beneath the initial rupture point of the main shock. In addition,there are obvious low velocity anomalies in the middle and upper crust of northern Qiaojia.

关 键 词：双差层析成像 巧家地震 鲁甸地震 震源区 速度结构 

分 类 号：P315.31[天文地球—地震学]