云南2020年巧家M_(S)5.0地震序列发震构造及其与2014年鲁甸M_(S)6.5地震的关系  

Seismogenic mechanism of the 2020 Qiaojia M_(S)5.0 earthquake sequence and its relationship with the 2014 Ludian M_(S)6.5 earthquake in Yunnan

作　　者：宋倩 梁姗姗[2] 于湘伟 章文波 李春来[3] SONG Qian;LIANG ShanShan;YU XiangWei;ZHANG WenBo;LI ChunLai(College of Earth and Planetary Sciences,University of Chinese Academy of Sciences,Beijing 100049,China;China Earthquake Networks Center,Beijing 100045,China;Institute of Geophysics,China Earthquake Administration,Beijing 100081,China)

机构地区：[1]中国科学院大学地球与行星科学学院,北京100049 [2]中国地震台网中心,北京100045 [3]中国地震局地球物理研究所,北京100081

出　　处：《地球物理学报》2022年第4期1303-1324,共22页Chinese Journal of Geophysics

基　　金：国家自然科学基金项目(41374105,42074062);国家自然科学基金地震联合基金重点项目(U2039208)联合资助.

摘　　要：本文联合地震震相报告数据与波形互相关数据,采用绝对定位和相对定位结合的方法,对2020年云南巧家M_(S)5.0地震以及震后一个月的余震序列进行了重定位研究,并结合距主震最近的2014年鲁甸M_(S)6.5地震序列特征对巧家地震的发震机制进行了深入讨论.重定位结果显示,巧家M_(S)5.0主震位于27.19°N,103.17°E,震源深度约为11.9 km,余震震中优势分布方向为近EW向,在深度方向上主要分布在5~10 km深度范围内,整体呈现较为直立的分布形态.重定位后巧家地震序列在N-S、E-W和U-D三个方向上的定位误差分别为:0.64 km、1.06 km和1.94 km.主震震源机制解展示出节面Ⅰ的走向/倾角/滑动角为176°/70°/-13°,节面Ⅱ的走向/倾角/滑动角为270°/78°/-160°,基于重定位后余震的优势分布方向,本文认为巧家M_(S)5.0地震为与节面Ⅱ参数相近的一次较高角度并以右旋走滑性质为主,发生在上地壳的浅源地震事件.余震序列重定位结果还进一步揭示了巧家地震造成的破裂分为南北两段,破裂方向由东到西,且两段破裂均未破裂到地表,其中南侧破裂较北侧破裂倾角更大且埋深更深,而北侧破裂的时间则短于南侧破裂.此次巧家地震余震序列优势分布方向与2014年鲁甸M_(S)6.5地震序列共轭破裂的近EW向分支方向高度相似,两个地震的主压应力方向相一致,结合以往鲁甸地震序列的研究结果,本文认为鲁甸地震对巧家地震的触发可能性较小.因此,2020年巧家M_(S)5.0地震是该区域块体运动造成的挤压应力累积作用下的一次应力释放过程,产生的破裂为与包谷垴—小河断裂成锐角形式的撕裂断层.Based on the seismic phase and waveform cross-correlation data,the 2020 Qiaojia M_(S)5.0 earthquake in Yunnan province and the aftershock sequence following the mainshock in a month are relocated by jointly using the absolute and relative relocated methods.We provide an insight into the seismogenic mechanism of the Qiaojia earthquake in relation to the characteristics of the 2014 Ludian M_(S)6.5 earthquake sequence,which was the closest spatially to the epicenter of the Qiaojia mainshock.The relocation results show that the mainshock was located at 27.19°N,103.17°E,with a focal depth of about 11.9 km,and that the dominant distribution of the aftershocks was in the near EW direction,with the overall distribution mainly in the 5~10 km range in the depth.The relocation errors of the Qiaojia earthquake sequence are 0.64 km,1.06 km and 1.94 km in the N-S,E-W and U-D directions,respectively.The focal mechanism solution of the mainshock shows a strike/dip/rake angle of 176°/70°/-13°for nodal planeⅠand 270°/78°/-160°for nodal planeⅡ.Combined with the dominant distribution of aftershocks after relocation,it is suggested that the Qiaojia M_(S)5.0 earthquake was a shallow event in the upper crust with a high angle and predominantly right-lateral strike-slip,which is similar to the parameters of nodal planeⅡ.The results of the aftershock sequence relocation further reveal that the source rupture caused by the Qiaojia earthquake was divided into the northern and southern segments,with the rupture direction running from east to west,and neither rupture reached the surface.The southern segment is buried deeper than the northern one,and its dip angle is also larger than that of the northern segment,while the northern rupture is shorter in duration than the southern rupture.The dominantly distributed direction of the aftershock sequence of the Qiaojia earthquake is highly similar to the nearly EW branch of the conjugate rupture of the 2014 Ludian M_(S)6.5 earthquake sequence,and the compressive principal stress dire

关 键 词：2020年巧家M_(S)5.0地震 地震序列重定位 震源机制解 发震机制 

分 类 号：P315[天文地球—地震学]