地震研究

为揭示2021年云南漾濞MS6.4地震的发震背景及其与区域应力场的关系,搜集5月18日14时28分至6月8日5时53分的地震序列,采用P波初动反演震源机制解的方法,计算得到漾濞地震前后85次MS≥2.5地震的震源机制解。根据本次地震序列的震源机制解和近10年内滇西北地区地震的震源机制解,利用网格搜索法反演了该区域的应力场,最后模拟了主震的震源机制与区域应力场的关系。结果表明:该区域主压应力方向为近南北向,主张应力轴方向为近东西向。漾濞主震发生在剪应力最大的区域,且剪应力的滑动角与发震节面的滑动角之差较小,说明此次地震是在构造应力场作用下发生在剪应力最大释放节面上。

In order to reveal the seismogenic background of the Yangbi MS6.4 earthquake in Yunnan Province and its relationship with the surrounding stress field,the dataset of the seismic sequence from 14:28 on May 18 to 5:53 on June 8 is collected.The focal mechanism solutions of 85 earthquakes with MS≥2.5 before and after the MS6.4 main shock are calculated by using the method of P-wave initial motion.Then,according to the focal mechanism solution,the stress field in the source region is inverted by using the grid search method.Finally,the focal mechanism of the main shock and the stress field around it are simulated.The results show that the direction of the main compressive stress is near NS direction,and the extensional stress axis is near EW direction.This result is roughly the same as that of the stress field in the mainland of China.Through the simulation of the stress field and focal mechanism,it is found that the main shock basically occurred in the area with the nearly largest shear stress,and the difference between the direction of the shear stress and the slip direction of the mainshock was small,which indicated that by the action of the tectonic stress field,the mainshock occurred on the nodal plane with maximum shear stress releas.

引言
1 方法及数据
2 震源机制解
3 应力场反演
4 震源机制与应力场的关系
5 结论与讨论

表1 震源机制解计算时使用的速度模型<br/>Tab.1 Velocity model used for the calculation of focal mechanism solution

表1 震源机制解计算时使用的速度模型
Tab.1 Velocity model used for the calculation of focal mechanism solution

图1 本文选取台站位置分布<br/>Fig.1 Distribution of stations in this study

图1 本文选取台站位置分布
Fig.1 Distribution of stations in this study

表2 根据P波初动求解出的震源机制解<br/><br/>Tab.2 Focal mechanism solutions determinede by inital motion of P-wave data

表2 根据P波初动求解出的震源机制解

Tab.2 Focal mechanism solutions determinede by inital motion of P-wave data

图2 MS≥3.0地震的震源机制解及其分布<br/>Fig.2 Focal mechanism solutions of the earthqakes with MS≥3.0 and their distribution

图2 MS≥3.0地震的震源机制解及其分布
Fig.2 Focal mechanism solutions of the earthqakes with MS≥3.0 and their distribution

表3 本文所求漾濞地震主震震源机制解和其它研究机构和个人结果的比较<br/>Tab.3 Focal mechanism solutions got in this paper and the ones given by institutes and other authors

表3 本文所求漾濞地震主震震源机制解和其它研究机构和个人结果的比较
Tab.3 Focal mechanism solutions got in this paper and the ones given by institutes and other authors

图3 震源机制解的P轴(a)和T轴分布(b)<br/>Fig.3 Distribution of P-axis(a)and T-axis(b)of focal mechanism solution

图3 震源机制解的P轴(a)和T轴分布(b)
Fig.3 Distribution of P-axis(a)and T-axis(b)of focal mechanism solution

表4 滇西北地区地震的震源机制解(据GCMT)<br/>Tab.4 Focal solutions in Northwest Yunnan by GCMT

表4 滇西北地区地震的震源机制解(据GCMT)
Tab.4 Focal solutions in Northwest Yunnan by GCMT

图4 漾濞地震应力场反演结果(a)及三维示意图(b)<br/>Fig.4 Results from stress field inversion of Yangbi earthquake(a)and 3D diagram(b)through focal mechanism solution

图4 漾濞地震应力场反演结果(a)及三维示意图(b)
Fig.4 Results from stress field inversion of Yangbi earthquake(a)and 3D diagram(b)through focal mechanism solution

图5 云南漾濞震源区应力体系下的震源机制解以及相对剪应力(a)和相对正应力(b)的分布<br/>Fig.5 Relative shear stress and focal mechanism solution(a),normal stress under stress and focal mechanism solution(b)in Yangbi area,Yunnan Province

图5 云南漾濞震源区应力体系下的震源机制解以及相对剪应力(a)和相对正应力(b)的分布
Fig.5 Relative shear stress and focal mechanism solution(a),normal stress under stress and focal mechanism solution(b)in Yangbi area,Yunnan Province

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备注

引言

1 方法及数据

2 震源机制解

3 应力场反演

4 震源机制与应力场的关系

5 结论与讨论

期刊信息