中强地震发震构造标志浅析——以2023年积石山M_(S)6.2地震为例  

Analysis of the Markers of Seismic Structures for Moderate Earthquakes:A Case Study of the 2023 Jishishan M_(s)6.2 Earthquake

作　　者：张军龙[1] 徐岳仁[1] 李文巧[1] 陈峰 ZHANG Jun-long;XU Yue-ren;LI Wen-qiao;CHEN Feng(Institute of Earthquake Forecasting,China Earthquake Administration,Beijing 100036,China)

机构地区：[1]中国地震局地震预测研究所,北京100036

出　　处：《地震》2024年第1期226-234,共9页Earthquake

基　　金：国家重点研发计划项目(2023YFC3012001-2,2023FY10150401);地震动力学国家重点实验室开放基金课题(LED2023B10);国家自然科学基金项目(41372215);中国地震局地震预测研究所基本科研业务费专项(CEAIEF20230403)。

摘　　要：地震地表破裂是地震发生的重要特征,是研究地震动力学、构造变形的重要手段。一般认为,M6 3/4以上的地震才会形成地表破裂。但近年来,也有M6.0左右的地震发生了地表破裂。本文旨在探讨中强地震地表破裂的识别方法。中强地震发震构造的识别具有一定的挑战性,主要表现在以下几个方面:(1)中强地震地表破裂的规模(位错量、宽度、长度和深度)较小,容易被黄土层厚覆盖,掩盖地表破裂的痕迹,不易识别;(2)非构造成因裂缝干扰,使得难以区分构造成因地表破裂。本文以2023年积石山M_(S)6.2地震为例,对中强地震构造成因破裂的识别标志进行了初步分析,提出了以下识别标志:(1)地表破裂几何展布和剖面形态,地震伴生的次生灾害(滑坡、崩塌、砂土液化等)的线性分布为识别发震构造提供参考和线索;(2)地表破裂沿破裂走向呈现稳定地穿越不同地貌单元,至少穿越一条沟谷等低凹地貌;(3)地表破裂在地质剖面上表现出稳定的产状;(4)地表破裂伴生构造形态,地表沿破裂发育雁列式褶皱(挤压鼓包)与张裂缝交替出现的现象。本文提出的识别标志为中强地震发震构造的识别提供了新的思路。Surface rupture is an important feature of earthquake occurrence,and a valuable tool for studying earthquake dynamics and tectonic deformation.It is generally believed that surface ruptures are only formed by earthquakes with magnitudes of M6 3/4 or greater.However,in recent years,surface ruptures have also been observed in earthquakes with magnitudes of M6.0 or less.This study aims to explore the methods for identifying sur-face ruptures in moderate earthquakes.The identification of the seismic structures of mod-erate earthquakes is challenging,mainly due to the following factors:①the relatively small scale of surface ruptures in moderate earthquakes(such as displacement,width,length,and depth),making them easily covered by thick loess and hidden;②non-tectonic fractures interfere with the identification of tectonic fractures.In this study,we conducted a preliminary analysis of the identification markers of the seismic structures of moderate earthquakes based on the Jishishan M_(s)6.2 earthquake.We proposed the following identifi-cation markers.①Geometric distribution and profile morphology of surface ruptures,lin-ear distribution of secondary disasters(landslides,collapses,sand liquefaction,etc.)as-sociated with earthquakes provides references and clues for identifying the seismic struc-ture;②the rupture runs stably across different geomorphic units along the rupture direction and at least crosses one low terrain such as a gully;③the rupture on the geological profile shows a stable dip;④tectonic morphology associated with surface ruptures that develops alternating echelons folds(compressional mounds)and tension cracks along the rupture.The identification markers proposed in this study provide new ideas for the iden-tification of the seismic structures of moderate earthquakes.

关 键 词：青藏高原 拉脊山断裂带 2023年积石山M_(S)6.2地震 发震构造 地震地表破裂 

分 类 号：P315.2[天文地球—地震学]