2017年九寨沟M_S7.0地震震源区速度结构与余震分布  

Velocity structures and aftershock distribution in the source region of the 2017 Jiuzhaigou M_S7.0 earthquake

作　　者：王伟平[1] 杨建思[1] 彭朝勇[1] 郑钰[1] 徐志强[1] 姜旭东[1] Wang Weiping;Yang Jiansi;Peng Chaoyong;Zheng Yu;Xu Zhiqiang;Jiang Xudong(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》2019年第1期1-12,共12页Acta Seismologica Sinica

基　　金：国家自然科学基金(41874075);中国地震局运维项目(2200407)联合资助

摘　　要：采用九寨沟M_S7.0 (M_W6.5)地震的余震直达P波、S波走时数据,通过体波走时层析成像方法,获得了震源区及其邻区的P波和S波速度结构,并利用成像结果对余震进行了重定位。结果显示:余震主要集中分布于高、低速异常交界处偏低速异常一侧,呈走向NNW,倾向SW,倾角较高的分布特征;余震序列两侧的P波、S波速度结构揭示了发震断层两侧介质性质的差异,即上盘为刚性较强的高地震波速度区,下盘为刚性较弱的低地震波速度区。由余震分布特征和地震波速度结构推断:九寨沟地震发生在上地壳底部,发震断层具有上盘地震波速度高、下盘地震波速度低的特征;主震引起的后续破裂在上地壳内部的剧烈形变区内传播,破裂能量终止于25 km深度附近。Using the arrival times from the aftershocks of 2017 Jiuzhaigou M_S7.0(M_W6.5)earthquake,the P-and S-wave velocity structures in the source region and its adjacent area are obtained by means of the body wave tomography method. The results show that the aftershocks,characterized by NNW-striking,SW-trending and a high dip angle,are mainly concentrated on one side of the low-velocity anomalies at the intersection of high-and low-velocity anomalies. The P-and S-wave velocity structures reveal the differences of crustal property on both sides of the seismogenic fault:the hanging-wall is a high-velocity zone with strong rigidity while the footwall is a low-velocity zone with weak rigidity. According to the distribution of aftershocks and the seismic velocity structure,it can be inferred ultimately that the 2017 Jiuzhaigou M_S7.0 earthquake occurred on the lower interface of the upper crust,following with the rupture propagated in a dramatically deformed area in the upper crust and terminated near the depth of 25 km,and the seismogenic fault has the property of low-velocity hanging-wall and highvelocity footwall.

关 键 词：九寨沟地震 层析成像 余震重定位 地震波速度 

分 类 号：P315.2[天文地球—地震学]