荣昌及周边三维速度结构初步研究  

A PRELIMINARY STUDY ON 3D VELOCITY STRUCTURE OF RONGCHANG AND ITS ADJACENT AREA

作　　者：李翠平 唐茂云 郭卫英 王小龙 董蕾 LI Cui-ping;TANG Mao-yun;GUO Wei-ying;WANG Xiao-long;DONG Lei(Chongqing Earthquake Agency,Chongqing 401147,China)

机构地区：[1]重庆市地震局,重庆401147

出　　处：《地震地质》2022年第1期205-219,共15页Seismology and Geology

基　　金：震情跟踪定向工作任务(2020010131);重庆市地震局创新团队共同资助。

摘　　要：文中基于2008年1月—2020年6月重庆区域固定台网、流动台网及自贡地方台网记录的1786个地震事件的P波和S波到时数据,采用双差层析成像反演了荣昌及周边精细的三维P波速度结构和地震事件的重定位结果。研究结果显示,荣昌地区沉积盖层与结晶基底的分界深度为12km,华蓥山基底断裂东、西两侧的速度结构在7~13km深度处差异较大,与前人的研究结果和荣昌地区的地震反射剖面特征基本一致。上地壳浅表层P波速度结构横向差异变化较大,在螺观山背斜轴部的螺2注水井附近为高速区,分布深度为3~7km。地震重定位结果显示中等地震主要分布在高、低速交界地区,广顺横断层北侧的地震分布与螺2注水井附近的高速体展布一致,均沿着螺观山北翼隐伏断层的倾向分布,推测该断层是废水下渗的主要通道,其下渗深度达7km。An M_(S)4.9 earthquake occurred at 08:17 on the December 27,2016 in Rongchang District,Chongqing,and the epicenter is located in the north central section of Huayingshan basement fault system on the eastern margin of Sichuan Basin.The seismicity shown in the historical earthquake catalogue was originally very weak in this area.Since the late 1980s,due to the impact of waste water reinjection in the natural gas field,earthquakes of magnitude≥4.0 occurred frequently and 14 earthquakes with M_(S)≥4.0 have occurred,the largest of which was Rongchang M_(S)5.0 earthquake in 1997.In this paper,the fine three-dimensional P-wave velocity structures and relocation results of seismic events in Rongchang and its surrounding areas are inversed by double difference tomography method,based on the P-wave and S-wave arrival time data of 1786 seismic events recorded by Chongqing regional fixed network,mobile network and Zigong local network from January 2008 to June 2020.The results show that:1)The distribution of high-velocity and low-velocity zones within 4km depth is significantly different from that below 7~13km depth.The P-wave high-velocity zone at 4km depth is mainly distributed in Renyi-Rongchang area,where there are four water injection wells,a major concentration area of continuous water injection in Rongchang since 2008.The range of Renyi-Rongchang high velocity zone significantly gets narrowed at the 7km depth and is obviously different from that at the shallow surface.The velocity structures on the east and west sides of Huayingshan basement fault vary greatly from 7 to 13km.The P-wave velocity structures of different sections across Huayingshan basement fault all indicate that the depth of the interface between the sedimentary cover and crystalline basement is 12km in Rongchang area,which is basically consistent with the previous research results and the characteristics of seismic reflection profiles in Rongchang area.The inversed velocity structures well mirror the shape of Luoguanshan fold,and further confirm t

关 键 词：双差层析成像 P波速度结构 地震定位 荣昌及周边 

分 类 号：P315.2[天文地球—地震学]