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《地震研究》[ISSN:1000-0666/CN:53-1062/P]

卷:

47

期数:

2024年04期

页码:

483-492

栏目:

出版日期:

2024-12-01

文章信息/Info

Title:

Study on the Stress State before the 2022,Lushan,Sichuan M_S6.1 Earthquake

作者:

张致伟¹; 2; 曾宪伟³; 王迪¹; 路茜¹; 王玮铭¹; 杨鹏¹; 龙锋¹

(1.四川省地震局,四川 成都 610041; 2.成都理工大学,四川 成都 610059; 3.宁夏回族自治区地震局,宁夏 银川 750001)

Author(s):

ZHANG Zhiwei¹; 2; ZENG Xianwei³; WANG Di¹; LU Qian¹; WANG Weiming¹; YANG Peng¹; LONG Feng¹

(1.Sichuan Earthquake Agency,Chengdu 610041,Sichuan,China)(2.College of Geophysics,Chengdu University of Technology,Chengdu 610059,Sichuan,China)(3.Earthquake Agency of Ningxia Hui Autonomous Region,Yinchuan 750001,Ningxia,China)

关键词:

芦山M_S6.1地震;  芦山M_S7.0地震;  震源机制解;  应力张量方差;  b值;  应力状态

Keywords:

the Lushan M_S6.1 earthquake;  the Lushan M_S7.0 earthquake;  focal mechanism solution;  stress tensor variance;  b value;  stress state

分类号:

P315.72

DOI:

10.20015/j.cnki.ISSN1000-0666.2024.0061

摘要:

为研究2022年6月1日四川芦山M_S6.1地震的孕育和发生过程,采用CAP方法反演了2013年芦山M_S7.0主震及M_S≥5.0余震的震源机制解,并基于应力张量方差与b值时空分布特征,探讨了芦山M_S6.1地震的力学机制和震源区的应力状态。结果表明:2022年芦山M_S6.1地震震源机制表现出与2013年芦山M_S7.0主震和5级余震相似的逆冲型破裂特征,压应力轴方位与龙门山断裂带南段区域应力场一致。2013年芦山M_S7.0地震后震中及附近的应力张量方差和b值长期处于低值状态,2022年芦山M_S6.1地震前震中及附近出现了应力张量方差和b值的低值异常,表明芦山余震区处于较高的应力水平。分析认为:巴颜喀拉块体持续东向运动受到华南块体的阻挡,震中所在区域长期受挤压逆冲作用,从而使芦山余震区长期处于应力积累的状态,芦山M_S6.1地震也是在这种动力学背景下发生的。

Abstract:

On June 1,2022,an M_S6.1 earthquake struck Lushan Country,Ya’an City of Sichuan Province.The earthquake is another significant event that occurred in the aftershock zone of the Lushan M_S7.0 earthquake on May 20,2013.To figure out the genesis and occurrence of the Lushan M_S6.1 earthquake,the CAP inversion method is used to calculate the focal mechanism of the Lushan M_S7.0 mainshock and its M_S≥5.0 aftershocks.And the mechanical mechanism and the stress state in the source area before the Lushan M_S6.1 earthquake are discussed based on the spatial and temporal distribution of the stress tensor variance and b value.The main insights are as follows:The focal mechanism of the Lushan M_S6.1 earthquake is featured as a thrust rupture,which is similar to the feature of the focal mechanism of the Lushan M_S7.0 earthquake and its M_S≥5.0 aftershocks.The direction of the principal compressive stress is consistent with the regional stress field of the southern section of the Longmenshan fault zone.The stress tensor variance and b value around the epicenter of the Lushan M_S7.0 earthquake are in a low state in a long period.What is more,shortly before the Lushan M_S6.1 earthquake,in its focal area there appeared low-value anomalies of the stress tensor variance and b value,indicating that the Lushan M_S7.0 earthquake aftershock zone had been keeping a higher stress level.The continuous eastward movement of the Bayan Har block is blocked by the South China block.Thus,the aftershock zone of the Lushan M_S7.0 earthquake is under the action of the horizontal extrusion and thrust,which leads to the long-term stress accumulation in this zone.Hence in this dynamic background,the Lushan M_S6.1 earthquake occurred.

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备注/Memo

备注/Memo:

收稿日期:2024-02-27.
基金项目:国家重点研发计划专题(2021YFC3000705-07); 国家自然科学基金地震科学联合基金(U2139203); 中国地震局“大震短临跟踪技术研究团队”项目; 四川省地震局“防震减灾公共服务平台建设创新团队”项目.
第一作者简介:张致伟(1983-),正高级工程师,主要从事地震综合预测与数字地震学应用研究.E-mail:zzw1983107@163.com.

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