2020年6月23日墨西哥M W7.4地震震源特征  

Source characteristics of the 23 June 2020 M W7.4 Mexico earthquake

作　　者：许力生[1] 张旭[1] 张喆 XU LiSheng;ZHANG Xu;ZHANG Zhe(Institute of Geophysics,China Earthquake Administration,Beijing 100081,China)

机构地区：[1]中国地震局地球物理研究所,北京100081

出　　处：《地球物理学报》2020年第11期4012-4022,共11页Chinese Journal of Geophysics

基　　金：中国地震局地球物理研究所基本业务费(DQJB19B08和DQJB19B20)资助.

摘　　要：2020年6月23日15时29分04秒(UTC),在墨西哥南部瓦哈卡州发生了一次震级为M W7.4的地震,我们利用全球地震台网(GSN)和国际数字地震台网联盟(FDSN)台网的长周期和宽频带P波数据反演分析了这次地震的震源机制、震源时间函数以及时空破裂过程.根据反演结果,这次地震的矩心震中位于15.96°N,95.89°W,矩心深度约为22 km;地震持续15 s左右,释放地震矩1.24×1020 N·m,相当于矩震级M W7.4;破裂过程比较简单,仅有一个走向和倾向方向尺度相当的凹凸体错动,最大位错达8.1 m,位于21 km深处.凹凸体破裂主要沿断层的滑动方向呈双侧破裂,两个优势破裂方向在地表投影的方位分别位于60°和270°左右.综合构造背景、震源位置、余震分布、震源机制以及时空破裂过程,我们相信这次地震是发生在北美大陆板块和太平洋海底板块相互作用的结果.海底板块朝着大约60°左右的方位运动,以大约22°的倾角插入大陆板块,造成一个凹凸体错动,形成了这次地震.At 15∶29∶04(UTC),June 23,2020,an M W7.4 earthquake occurred in the Oaxaca,southern Mexico.Based on the inversion of the P waveform data of the long-period and broadband stations of the Global Seismograph Network(GSN)and International Federation of Digital Seismograph Networks(FDSN)networks,we analyzed the focal mechanism,the source time function and the spatio-temporal rupture process of this earthquake.From the inversion and analysis,the earthquake had a centroid epicenter 15.96°N,95.89°W,and a centroid depth 22 km.This event lasted about 15 s,and released a scalar moment of 1.24×1020 N·m,yielding a magnitude M W7.4.The source process was quite simple,with only a single asperity being ruptured.The maximum slip reached 8.1 m,appearing at the depth of 21 km.The asperity ruptured bilaterally along the rake direction,producing similar dimensions in the strike and down-dip directions.The two predominant rupture directions on the fault plane led to two azimuths 60°and 270°,just as indicated by the analysis of the apparent source time functions.Combining the tectonic setting,the mainshock location,the aftershock distribution,and the focal mechanism and spatio-temporal rupture process,we believed that this earthquake was caused by the interaction between the North America continental block and the Pacific seafloor block.The seafloor block moved approximately to azimuth 60°,inserted with a dip of around 22°under the continental block,and ruptured a single asperity,producing the M W7.4 Mexico earthquake.

关 键 词：墨西哥M W7.4地震 矩心矩张量解 震源时间函数 时空破裂过程 

分 类 号：P315[天文地球—地震学]