采用模糊聚类算法确定2021年玛多地震序列的断层结构  

Geometry of Seismogenic Faults Determination of the 2021 Maduo Earthquake Sequence by Fuzzy Clustering Algorithm

作　　者：李佺洪 万永革 Li Quanhong;Wan Yongge(College of Earth Sciences,Institute of Disater Prevention,Sanhe 065201,China;Hebei Key Laboratory of Earthquake Dynamics,Sanhe 065201,China;Key Laboratory of Earth and Planetary Physics,Institute of Geology and Geophysics Chinese Academy of Sciences,Beijing 100029,China;College of Earth and Planetary Sciences,University of Chinese Academy of Sciences,Beijing 100049,China)

机构地区：[1]防灾科技学院地球科学学院,河北三河065201 [2]河北省地震动力学重点实验室,河北三河065201 [3]中国科学院地质与地球物理研究所地球与行星物理重点实验室,北京100029 [4]中国科学院大学地球与行星科学学院,北京100049

出　　处：《地球科学》2024年第9期3363-3376,共14页Earth Science

基　　金：国家自然科学基金项目(Nos.42174074,41674055);河北省地震科技星火计划项目(No.DZ20200827053);中央高校科研业务费专项(No.ZY20215117);河北省地震动力学重点实验室开放基金项目(No.FZ212105).

摘　　要：为更深入理解青海玛多区域的地质构造,准确确定该区域的各个分支断层面形状以及断层面参数是关键.本研究按照成丛小震发生在断层面邻近区域的原则,基于模糊聚类算法聚类数据并确定断层面的方法对2021年青海玛多Ms7.4级地震序列进行断层面形状求解,得到了各个分级下的断层结构.然后将研究区域的应力场投影到获得的断层面上,得到了各个断层面的相对剪应力和正应力.结果表明本次地震主干断层面破裂长度为163.71 km,总体走向为285.81°,倾角为85.62°,断层面主要分布于昆仑山口‒江错断裂上.该地震序列的东西两侧表现有明显的分叉现象,针对这一较为复杂的断层结构,通过区域划分和模糊聚类数目的各种尝试,得到了划分为6个断层面的模糊聚类求解断层面结果.将研究区域的构造应力场结果投影到6个断层面上,发现这些断层面上相对剪应力普遍大于相对正应力.由此推断本次地震主要是由构造应力场作用引起,而位于西端分叉处北支的小断裂是主破裂引发的分支破裂,由于本次破裂具有左旋走滑运动性质,使断层东段东北部出现了尾端拉张,导致东段分叉上形成了两个小断层.本研究中通过模糊聚类方法得出的断层参数与其他机构作者数据一致性较高.该方法基于大量地震序列数据可较为准确地得出断层面信息且可操作性高,在未来地震构造、断层面确定以及分析中具有重要意义.To gain a deeper understanding of the geological structure in the Maduo region of Qinghai,it is crucial to accurately determine the shapes and parameters of each branch fault planes in the area.Based on the principle that clusters of small earthquakes occur near the fault plane,by using the fuzzy clustering algorithm to cluster the seismic event,the geometry parameters of the fault planes of the 2021 Ms7.4 Qinghai Maduo earthquake sequence are determined.By projecting the stress field in study area onto the obtained fault planes,the relative shear stress and normal stress of each fault plane are obtained.The results show that the overall fault plane of these 2021 Maduo earthquake is mainly distributed on the Kunlun Pass-Jiangcuo fault,with rupture length of 163.71 km,strike of 285.81°,and dip angle of 85.62°.There are obvious bifurcations on the east and west sides of the earthquake distribution area.For the complex fault structure,we made various attempts through the fuzzy clustering algorithm,and obtained the fault plane solution by fuzzy clustering with 6 fault planes.By projecting the tectonic stress field onto the 6 obtained fault planes,we found that the relative shear stress on these fault planes is generally greater than the relative normal stress.Therefore,it is speculated that the earthquake was mainly caused by the tectonic stress field,and the small fault in the north branch at the western end of the bifurcation is the branch rupture caused by the main rupture.Due to the left-lateral strike-slip nature of this rupture,tail extension appeared in the northeastern part of the eastern segment of the fault,resulting in the formation of the 2 small faults on the bifurcation of the eastern segment.The fault parameters obtained by the fuzzy clustering method in this study are also highly consistent with the data of other authors and institutions.This method is an accurate and maneuverable method to obtain fault plane information based on a large amount of seismic sequence data.This method will have importan

关 键 词：模糊聚类 断裂带形状 断层面解 玛多Ms7.4级地震 发震断层 地震学. 

分 类 号：P315.2[天文地球—地震学]