2023年甘肃积石山M_(s)6.2地震震源区的三维速度结构及其发震构造  

Three-dimensional velocity structure and seismogenic structure of the 2023 Gansu Jishishan M_(s)6.2 earthquake source area

作　　者：蔡光耀 王未来[1,2] 吴建平 张龙[1,2] 包晶晶 孟繁昌 刘慧杰 CAI GuangYao;WANG WeiLai;WU JianPing;ZHANG Long;BAO JingJing;MENG FanChang;LIU HuiJie(Institute of Geophysics,China Earthquake Administration,Beijing 100081,China;National Field Scientific Observation Research Station of Earth Science at Beijing Baijiatuan,Beijing 100081,China;Geophysical Exploration Center,China Earthquake Administration,Zhengzhou 450002,China)

机构地区：[1]中国地震局地球物理研究所,北京100081 [2]北京白家疃地球科学国家野外科学观测研究站,北京100081 [3]中国地震局地球物理勘探中心,郑州450002

出　　处：《地球物理学报》2024年第11期4148-4159,共12页Chinese Journal of Geophysics

基　　金：国家重点研发计划项目(2022YFC3003501);甘肃积石山6.2级地震科学考察(DQJB23Y45)项目资助。

摘　　要：2023年12月18日23时59分, 在甘肃积石山县拉脊山南段积石山东缘断裂附近发生了M_(s)6.2地震.为了探究本次地震的发震构造、孕震环境以及余震序列与深部结构的关系, 本文使用基于固定台站、预警台站和临时布设的密集台阵构建的地震事件资料, 采用双差层析成像方法开展地震定位和三维速度结构研究.重定位后, 余震序列近似呈SE-NW方向展布, 总长度约15 km, 震源优势深度分布范围为8~14 km, 平均深度为10.4 km.主破裂北侧余震条带和主破裂附近余震序列的震源深度存在错断, 二者倾向在空间上近似垂直.东北倾的大河家断裂是主震的发震断层, 主破裂北侧余震条带发生在一条西南倾的反冲盲断层上.余震序列基本发生在高速和低泊松比异常内, 且高速异常和余震序列的形态高度吻合, 速度结构的非均匀性是控制本次地震和余震形态的主要深部构造因素.本次地震是在挤压构造背景下, 上地壳高速和低泊松比异常体内进行应力积累和释放, 从而发生的一次典型的逆冲型地震事件.On 18 December 2023, at 23∶59, the M_(s)6.2 earthquake occurred near the Jishishan Eastern Margin Fault in the southern section of the Lajishan in Jishishan County, Gansu. To investigate this earthquake's seismogenic tectonic and seismogenic environment and the relationship between the aftershock sequences and the deep structure. This paper uses the earthquake event data constructed on permanent stations, warning stations, and temporarily deployed dense station arrays, using double-difference tomography to carry out earthquake location and three-dimensional velocity structure studies. After relocation, the aftershock sequence spreads approximately in the SE-NW direction with a total length of about 15 km. The depth distribution of the earthquake dominance ranges from 8~14 km, and the average depth is 10.4 km. There is a dislocation in the earthquake depths between the aftershock strip north of the main rupture and the aftershock sequence near the main rupture, and the two dips are approximately vertical in space. The northeast-dipping Dahejia fault is the seismogenic fault of the main rupture, and the aftershock strip north of the main rupture presumably occurred on a southwest-dipping recoil blind fault. The aftershock sequences basically occurred within the high-velocity and low Poisson's ratio anomalies, the high-velocity anomalies and the aftershock sequences are highly coincident. The non-uniformity of the velocity structure is the main deep tectonic factor controlling the pattern of this earthquake and aftershocks. This earthquake was supposed to be a typical recoil-type event that occurred in the context of extrusion tectonics, with stress accumulation and release within a high-velocity and low Poisson's ratio anomaly in the upper crust.

关 键 词：甘肃积石山M_(s)6.2地震 积石山东缘断裂 地震重定位 速度结构 发震断层 

分 类 号：P315[天文地球—地震学]