云南漾濞6.4级地震震源区及周边的重力均衡特征  

THE GRAVITY ISOSTATIC CHARACTERISTICS OF THE EPICENTER AND ITS SURROUNDING REGIONS OF THE YANGBI M_(S)6.4,YUNNAN EARTHQUAKE

作　　者：石磊[1,2] 李永华 张瑞青[1,2] SHI Lei;LI Yong-hua;ZHANG Rui-qing(Institute of Geophysics,China Earthquake Administration,Beijing 100081,China;Key Laboratory of Earthquake Source Physics,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 [2]中国地震局震源物理重点实验室,北京100081

出　　处：《地震地质》2021年第5期1140-1156,共17页Seismology and Geology

基　　金：基金资助:国家自然科学基金(41874097);国家自然科学基金(41874108);中国地震局地球物理研究所基本科研业务专项(DQJB19B37)共同资助。

摘　　要：2021年5月21日云南漾濞发生了6.4级地震,造成35人伤亡,受灾面积近6500km^(2)。文中基于WGM2012布格重力异常、ETOPO1高程和接收函数估计得到的莫霍面深度资料,考虑密度差的横向变化,计算得到了该地震震源区及周边地区的重力均衡异常。研究结果表明:地壳平均密度与上地幔顶部密度差的变化范围为0.3~0.55g/cm^(3),漾濞地震震源区位于密度差过渡带。研究区6.5级及以上地震分布在重力均衡异常(艾里均衡理论莫霍面深度与接收函数H-κ叠加扫描法得到莫霍面的深度之差)梯度带的频率高于极值区。漾濞地震震源区处于均衡异常为4km的梯度带上,且梯度带与维西-乔后-巍山断裂带的走向基本一致。重力均衡异常梯度带为异常变化较快的地区,我们推测这些地区可能处于不稳定状态,有利于应变能的积累,为使地壳达到均衡,多从这些地方开始调整,从而导致地震的发生。The May 21,2021,M_(S)6.4 earthquake occurred in Yangbi,Yunnan,which caused 35 people died and possibly affected an area of 6500 square kilometers.The hypocenter is located near the Weixi-Qiaohou-Weishan Fault which is the northern extension of the Red River Fault.However,the existing data show that this earthquake may not occur on the Weixi-Qiaohou-Weishan Fault.Further research is needed to explore the seismogenic fault.It is of great significance to understand the crustal structure and physical properties of the epicenter and its surrounding regions.Affected by the Indian plate pushing on the Tibet,the southeastern margin of Tibetan plateau is characterized by intense intracontinental deformation,many deep faults and strong seismic activities.Gravity is one of the methods to study the crust structure and deep seismogenic environment.Many researches have been carried out in the study area,such as on the characteristics of gravity field,Moho depth,density structure,and isostatic anomaly.Gravity isostasy can reflect the crustal structure and its relationship with tectonic stress,which relates to seismic activities.However,the relationship between isostasy anomaly and earthquake distribution is still controversial.Some researches show that the Wenchuan earthquake locates in the extreme value region of isostatic anomaly.They believe the places where the difference between the theoretical and actual Moho depth is large are more likely to generate earthquakes.Other studies find that strong earthquakes in the western Sichuan and eastern Tibetan plateau occur mostly in the isostatic anomaly gradient regions,where the earthquake frequency is obviously higher than the extreme value regions.The crust-mantle density contrast is often taken as a constant in calculating Airy theoretical crustal thickness.The crust-mantle density contrast is inconsistent calculated with different data and methods.The gravity isostasy anomaly,which takes into account the density lateral variation,can better reflect the real structure.In this pa

关 键 词：漾濞地震 壳幔密度差 艾里均衡 均衡异常 

分 类 号：P315.726[天文地球—地震学]