2020年呼和浩特市和林格尔M_(L)4.5地震破裂方向性测定及发震构造分析  

Determination of Rupture Direction and Seismogenic Structure of the 2020 Heerlinger M_(L)4.5 Earthquake in Hohhot,Inner Mongolia

作　　者：杨彦明[1] 苏淑娟 王磊[1] YANG Yan-ming;SU Shu-juan;WANG Lei(Earthquake Agency of Inner Mongolia Autonomous Region,Hohhot 010010,China;Yantai Earthquake Monitoring Center Station,Shandong Earthquake Agency,Yantai 264000,China)

机构地区：[1]内蒙古自治区地震局,内蒙古呼和浩特010010 [2]山东省地震局烟台地震监测中心站,山东烟台264000

出　　处：《地震》2024年第2期63-85,共23页Earthquake

基　　金：中国地震局地震预测开放基金项目(XH23077D);内蒙古自治区地震局局长基金重点项目(2022(ZD)JP01);内蒙古自治区自然科学基金项目(2023MS04012);内蒙古自治区人才开发基金项目(内人社办函[2023]182号)。

摘　　要：本文基于区域数字地震台网波形数据,在三维空间内利用gCAP反演方法获得2020年3月30日和林格尔M_(L)4.5地震矩心的空间精细位置为40.131°N, 111.922°E,深度为13 km。最佳震源机制解节面Ⅰ为走向279°,倾角41°,滑动角-27°;节面Ⅱ为走向30°,倾角72°,滑动角-127°;矩震级MW3.98。采用双差定位法对主震和余震序列进行重定位,获得19个地震事件的重定位结果。研究表明,主震震源参数为40.136°N, 111.858°E,震源深度为11.718 km;余震序列沿NW—SE方向双向扩展,地下破裂长度约为4.6 km;深度剖面显示,主震位于余震区中部,主破裂同时向上和向下扩展,深度分布范围为4~17 km。利用Hypocenter-Centroid方法对地震发震断层进行快速判断,20组测定结果均显示NW走向的节面Ⅰ为发震断层面。综合震源区地质构造、余震序列分布、区域构造应力场及三维地壳结构等研究结果,推断和林格尔M_(L)4.5地震的发震断层是一条沿NW向延伸的隐伏断裂。本次地震是一次左旋走滑、带正断分量的事件。地震发生于地壳内波速高低转换的过渡区,位于偏高速体一侧。综合分析认为,流体物质的涌入是引发2020年和林格尔M_(L)4.5地震的关键因素,而复杂的断层结构不仅为流体运移提供了通道,且控制着地震的发生及地震序列的空间展布。Based on the observed waveform data of the regional digital seismic networks, the gCAP inversion method is used in three-dimensional space to obtain the centroid fine position of the Helingeer M_(L)4.5 earthquake on March 30, 2020, which is 40.131°N, 111.922°E, and the depth is 13 km. The strike/dip/slip of the first nodal plane are 279°/41°/-27° and those of the second nodal plane are 30°/72°/-127°. The moment magnitude is M_W3.98. The double-difference method named HypoDD algorithm is used to relocate the main shock and aftershock sequences, and the relocation results of 19 seismics events are obtained. The results show that the focal parameters of main shock are 111.858°E and 40.136°N, and the focal depth is 11.718 km. The aftershock sequences are bilaterally extended along NW—SE direction and the subsurface rupture length is 4.6 km. The depth profile shows that the main shock is located in the middle of the aftershock area. The main rupture extends upward and downward simultaneously, and the depth distribution of the sequence ranges from 4 km to 17 km. The 20 sets of measurement results show that the NW-trending nodal plane Ⅰ is the seismogenic fault plane. Based on the research results of the geological structure of the focal area, the tectonic stress field and the three-dimensional crustal structure of the aftershock sequence distribution area, it is inferred that the seismogenic fault of the Helingeer M_(L)4.5 earthquake is a NW-trending buried fault and the event is a left-lateral strike-slip mechanism with normal fault component. The earthquake occurred in the transition zone of high and low wave velocity conversion in the crust, which is located on the side of the high velocity body. Comprehensive analysis shows that influx of fluid materials plays an important role in triggering the earthquake event, and the complex fault structure not only provides pathways for fluid migration, but also controls the occurrence of earthquakes and the spatial distribution of seismic sequences.

关 键 词：2020年和林格尔M_(L)4.5地震 Hypocenter-Centroid方法 震源机制解 发震构造 鄂尔多斯北缘 

分 类 号：P315.7[天文地球—地震学]