地震研究

2022年青海德令哈M_S6.0地震序列重定位及发震背景分析

黄浩¹,袁伏全¹,李丽²,赵燕杰¹,万玉杰¹,马建新¹,李启雷¹,胡维云¹,郭瑛霞¹

(1.青海省地震局,青海西宁 810017; 2.山西省地震局,山西太原 030021)

关键词：德令哈地震; 地震重定位; 震源机制; 发震背景; 青海

Earthquake Relocation and Seismic Tectonic Background of the 2022 Delingha M_S6.0 Earthquake Sequence

HUANG Hao¹,YUAN Fuquan¹,LI Li²,ZHAO Yanjie¹,WAN Yujie¹,MA Jianxin¹,LI Qilei¹,HU Weiyun¹,GUO Yingxia¹

(1.Qinghai Earthquake Agency,Xining 810017,Qinghai,China)(2.Shanxi Earthquake Agency,Taiyuan 030021,Shanxi,China)

Keywords：the Delingha earthquake; earthquake relocation; focal mechanism; seismic tectonic background; Qinghai

DOI: 10.20015/j.cnki.ISSN1000-0666.2023.0050

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参考文献

2022年1月23日、3月26日和4月15日青海省德令哈市分别发生MS5.8、MS6.0和MS5.4地震。采用CAP方法反演了MS6.0地震及6次MS≥3.7地震的震源机制解和震源矩心深度,利用双差定位方法重新定位了德令哈MS6.0地震序列的震源位置,初步分析了德令哈MS6.0地震序列的发震背景。震源机制结果显示,MS6.0地震震源机制解节面Ⅰ:走向174°/倾角80°/滑动角-156°,节面Ⅱ:走向79°/倾角66°/滑动角-11°,矩心深度6 km。地震重定位结果显示,德令哈MS6.0地震序列震中呈NS向展布、震源区北部为主体破裂区域。基于震源机制解、地震重定位结果和震源区附近局部发育NS向构造的特征,分析认为德令哈MS6.0地震序列的发震构造为一条NS向、高倾角的右旋走滑隐伏断层。

A 5.8-magnitude,a 6.0-magnitude,and a 5.4-magnitude earthquake occurred respectively on Jan.23,Mar.26 and Apr.15,2022 in Delingha city of Qinghai province.We firstly inverted the focal mechanisms and the centroid depth of the source of the MS6.0 main shock and other 6 MS≥3.7 aftershocks by the CAP method,then we relocated the sources of the MS6.0 earthquake sequence by the hypoDD method,and analyzed the characteristics of the focal mechanisms,the relocated source parameters and the seismogenic structure.The focal mechanism of the Delingha MS6.0 earthquake has 2 solutions:for the first nodal plane,strike is 174°,dip is 80°,rake is -156°.For the second nodal plane,strike is 79°,dip is 66°,rake is -11°.The centroid depth is 6 km.The sources of the MS6.0 earthquake sequence are mainly distributed in North-South direction.According to the focal mechanism,relocated source parameters,and the geological structure in the source region,the seismogenic structure of the MS6.0 earthquake sequence is a hidden fault with high dip angel in North-South direction.

引言
1 区域地质构造背景
2 震源机制解
3 德令哈M_S6.0地震序列重定位
4 结论

图1 研究区构造背景与M≥6.0历史地震震中分布<br/>Fig.1 Regional tectonic settings and epicenters of M≥6.0 historical earthquakes in the study area

图1 研究区构造背景与M≥6.0历史地震震中分布
Fig.1 Regional tectonic settings and epicenters of M≥6.0 historical earthquakes in the study area

表1 初始地壳速度结构<br/>Tab.1 Crustal velocity model

表1 初始地壳速度结构
Tab.1 Crustal velocity model

图2 德令哈MS5.8(a)、MS6.0(b)和MS5.4地震(c)矩张量反演中波形拟合误差随深度的变化<br/>Fig.2 The fitting error of the moment tensor inversion variating with the focal depth of the Delingha MS5.8(a),MS6.0(b)and MS5.4(c)earthquakes

图2 德令哈MS5.8(a)、MS6.0(b)和MS5.4地震(c)矩张量反演中波形拟合误差随深度的变化
Fig.2 The fitting error of the moment tensor inversion variating with the focal depth of the Delingha MS5.8(a),MS6.0(b)and MS5.4(c)earthquakes

图3 德令哈MS5.8(a)、MS6.0(b)和MS5.4(c)地震双力偶机制解及理论(红色)和实际(黑色)波形对比<br/>Fig.3 Double-coupled source mechanism solutions and comparison between the theoretical(red)and observed(black)waveforms of the Delingha MS5.8(a),MS6.0(b)and MS5.4(c)earthquakes

图3 德令哈MS5.8(a)、MS6.0(b)和MS5.4(c)地震双力偶机制解及理论(红色)和实际(黑色)波形对比
Fig.3 Double-coupled source mechanism solutions and comparison between the theoretical(red)and observed(black)waveforms of the Delingha MS5.8(a),MS6.0(b)and MS5.4(c)earthquakes

表2 不同机构得出的德令哈MS5.8、MS6.0和MS5.4地震震源机制解<br/>Tab.2 Focal mechanisms and focal depths of the Delingha MS5.8,MS6.0,MS5.4 earthquakes provided by differernt institutes

表2 不同机构得出的德令哈MS5.8、MS6.0和MS5.4地震震源机制解
Tab.2 Focal mechanisms and focal depths of the Delingha MS5.8,MS6.0,MS5.4 earthquakes provided by differernt institutes

图4 德令哈MS6.0地震、部分MS≥3.7地震及震中区1970年以来MS≥5.0地震震源机制解<br/>Fig.4 Focal mechanism solutions of the Delingha MS6.0 earthquake and some MS≥3.7 aftershocks and MS≥5.0 earthquakes in epicenter area since 1970

图4 德令哈MS6.0地震、部分MS≥3.7地震及震中区1970年以来MS≥5.0地震震源机制解
Fig.4 Focal mechanism solutions of the Delingha MS6.0 earthquake and some MS≥3.7 aftershocks and MS≥5.0 earthquakes in epicenter area since 1970

表3 德令哈MS6.0地震及部分MS≥3.7地震震源机制解<br/>Tab.3 Focal mechanism solutions of the Delingha MS6.0 earthquake and some MS≥3.7 aftershocks

表3 德令哈MS6.0地震及部分MS≥3.7地震震源机制解
Tab.3 Focal mechanism solutions of the Delingha MS6.0 earthquake and some MS≥3.7 aftershocks

图5 德令哈MS6.0地震震源区应力场反演的力轴投影<br/>Fig.5 The projection of the principal axes of the stress field inverted from the focal mechanism solutions in the epicentral area of the Delingha MS6.0 earthquake

图5 德令哈MS6.0地震震源区应力场反演的力轴投影
Fig.5 The projection of the principal axes of the stress field inverted from the focal mechanism solutions in the epicentral area of the Delingha MS6.0 earthquake

图6 德令哈MS6.0地震震中周围的台站分布<br/>Fig.6 Distribution of the seismic stations around the epicenter of the Delingha MS6.0 earthquake

图6 德令哈MS6.0地震震中周围的台站分布
Fig.6 Distribution of the seismic stations around the epicenter of the Delingha MS6.0 earthquake

表4 图 6中的台站代码及其对应的台站名称<br/>Tab.4 Stations and their codes marked in Figure 6

表4 图 6中的台站代码及其对应的台站名称
Tab.4 Stations and their codes marked in Figure 6

图7 德令哈MS6.0地震序列重定位前(a)、后(b)的震中分布<br/>Fig.7 Epicenters of the Delingha MS6.0 earthquake sequence before(a)and after(b)precise relocation

图7 德令哈MS6.0地震序列重定位前(a)、后(b)的震中分布
Fig.7 Epicenters of the Delingha MS6.0 earthquake sequence before(a)and after(b)precise relocation

图8 德令哈MS6.0地震序列重定位前(a)、后(b)的震源深度分布图<br/>Fig.8 Focal depths of the Delingha MS6.0 earthquake sequence before(a)and after(b)precise relocation

图8 德令哈MS6.0地震序列重定位前(a)、后(b)的震源深度分布图
Fig.8 Focal depths of the Delingha MS6.0 earthquake sequence before(a)and after(b)precise relocation

图9 重定位后的德令哈MS6.0地震序列余震分别沿AA'(a)、BB'(b)、CC'(c)、DD'(d)、EE'(e)、FF'(f)震源深度剖面图
Fig.9 Distribution of depths of the Delingha MS6.0 earthquake sequence along AA' profile(a),BB' profile(b),CC' profile(c),DD' profile(d),EE' profile(e)and FF' profile(f)after precise relocation