地震研究

利用云南地震台网提供的地震编目快报观测报告和地震事件波形数据,采用联合波形互相关分析的双差地震定位方法,对2021年5月21日云南漾濞MS6.4地震前3天至震后2天期间发生的地震事件进行了重定位,并基于两种不同的区域速度模型,采用CAP方法反演了序列中3次MS≥ 5.0地震的震源机制解和矩心深度。结果表明:双差重定位获得了漾濞地震序列中1 012次地震的精确位置,水平和垂直方向的定位误差分别为1.1 km和3.0 km。3次MS≥5.0地震的震源机制解和深度均有所不同,初步分析认为这可能是由断裂深浅部的结构、形态差异或地震破裂后震源区附近的应力调整或流体运移导致的断层成核破裂变化所致。综合地震重定位、震源机制解反演及区域活动构造资料,初步分析认为漾濞MS6.4地震的发震破裂面走向约为140°,倾角约为80°,滑动角约为-160°,发震断层可能为维西—乔后断裂中段的一条或多条次级断裂,且具有右旋走滑特征。

Using earthquake catalog and seismic waveforms data recorded by the Yunnan Seismic Network,we relocate the Yangbi,Yunnan MS6.4 earthquake sequence occurring from 18th to 23th May,2021 through the double-difference relocation algorithm and the cross-correlation analysis.We also invert the focal mechanisms and depths of the three MS≥5.0 events(including the mainshock)in the Yangbi earthquake sequence with the cut-and-paste(CAP)method.Then we obtain epicenters and focal depths of 1 012 events,with median relocation errors about 1.1 km and 3.0 km in horizontal and depth direction,respectively.The focal mechanisms and the depths of each of the three events inverted are slightly different,which could be attributed to the different fault structures between the shallow and the deep part of the seismogenic fault zone,or the stress adjustment or fluid migration after the mainshock.According to the double-difference relocation,CAP inversions and distribution of regional geological structures,we preliminary infer that the Weixi-Qiaohou Fault could be the seismogenic fault of the 2021 Yangbi MS6.4 earthquake sequence.The parameters of the Fault's fracture surface,strike/dip/slip,could be 140°/80°/-160°.

引言
1 数据选取和研究方法
2 CAP方法反演震源机制解
3 双差地震定位及不确定性分析
4 讨论
5 结论

图1 2021年漾濞MS6.4地震序列周边台站及断层分布<br/>Fig.1 Distribution of the faults,stations and epicenters of the 2021 Yangbi MS6.4 earthquake sequence in the study area

图1 2021年漾濞MS6.4地震序列周边台站及断层分布
Fig.1 Distribution of the faults,stations and epicenters of the 2021 Yangbi MS6.4 earthquake sequence in the study area

表1 漾濞MS6.4地震序列 4次MS≥5.0地震的发震时刻和震源位置(根据云南地震台网)<br/>Tab.1 Origin time and locations of four MS≥ 5.0 earthquakes in the Yangbi MS6.4 earthquake sequence (from Yunnan Seismic Network)

表1 漾濞MS6.4地震序列 4次MS≥5.0地震的发震时刻和震源位置(根据云南地震台网)
Tab.1 Origin time and locations of four MS≥ 5.0 earthquakes in the Yangbi MS6.4 earthquake sequence (from Yunnan Seismic Network)

图2 漾濞MS6.4地震序列原始震中分布(a)以及沿AA'(b)和BB'(c)剖面的深度剖面分布图<br/>Fig.2 Initial epicenter distribution(a),depth profiles along AA'(b)and BB'(c)of the Yangbi MS6.4 earthquake sequence

图2 漾濞MS6.4地震序列原始震中分布(a)以及沿AA'(b)和BB'(c)剖面的深度剖面分布图
Fig.2 Initial epicenter distribution(a),depth profiles along AA'(b)and BB'(c)of the Yangbi MS6.4 earthquake sequence

图3 漾濞MS6.4地震序列的P、S波震相走时<br/>Fig.3 Travel time of P- and S-phases of the Yangbi MS6.4 earthquake sequence

图3 漾濞MS6.4地震序列的P、S波震相走时
Fig.3 Travel time of P- and S-phases of the Yangbi MS6.4 earthquake sequence

图4 使用波形互相关分析得到漾濞MS6.4地震前142次地震的P、S波震相手动拾取误差分析<br/>Fig.4 Error distribution of the hand-picked P- and S-phases of 142 pre-shocks before the Yangbi MS6.4 mainshock derived from cross-correlation analysis

图4 使用波形互相关分析得到漾濞MS6.4地震前142次地震的P、S波震相手动拾取误差分析
Fig.4 Error distribution of the hand-picked P- and S-phases of 142 pre-shocks before the Yangbi MS6.4 mainshock derived from cross-correlation analysis

图5 CAP反演中用到的两种一维速度模型<br/>Fig.5 Two 1-D velocity models used in CAP inversions

图5 CAP反演中用到的两种一维速度模型
Fig.5 Two 1-D velocity models used in CAP inversions

图6 利用两种速度模型反演得到的漾濞MS6.4地震在震源深度7 km(a,模型A)和震源深度5 km(b,模型B)的部分理论(红线)和观测波形(黑线)的对比图<br/>Fig.6 Comparison between observed(black line)and synthetic(red line)seismograms of the MS6.4 mainshock at 7 km depth(a,model A),and at 5 km depth(b,model B)obtained by using CAP inversion

图6 利用两种速度模型反演得到的漾濞MS6.4地震在震源深度7 km(a,模型A)和震源深度5 km(b,模型B)的部分理论(红线)和观测波形(黑线)的对比图
Fig.6 Comparison between observed(black line)and synthetic(red line)seismograms of the MS6.4 mainshock at 7 km depth(a,model A),and at 5 km depth(b,model B)obtained by using CAP inversion

表2 利用CAP方法反演得到3次MS≥5.0地震的震源机制解<br/>Tab.1 Focal mechanisms of three Yangbi MS≥5.0 earthquakes inverted by using CAP method

表2 利用CAP方法反演得到3次MS≥5.0地震的震源机制解
Tab.1 Focal mechanisms of three Yangbi MS≥5.0 earthquakes inverted by using CAP method

图7 双差重定位后的震中分布(a)及震源沿AA'(b)、BB'(c)CC(d)及DD'(e)剖面的分布<br/>Fig.7 Epicentral distribution(a),and focal depth distribution along AA'(b),BB'(c),CC'(d)and DD'(d)profiles according to double-difference relocation

图7 双差重定位后的震中分布(a)及震源沿AA'(b)、BB'(c)CC(d)及DD'(e)剖面的分布
Fig.7 Epicentral distribution(a),and focal depth distribution along AA'(b),BB'(c),CC'(d)and DD'(d)profiles according to double-difference relocation

图8 漾濞MS6.4地震序列双差定位不确定性分析<br/>Fig.8 Uncertainty analysis of double-difference relocation of the Yangbi MS6.4 earthquake sequence

图8 漾濞MS6.4地震序列双差定位不确定性分析
Fig.8 Uncertainty analysis of double-difference relocation of the Yangbi MS6.4 earthquake sequence

常祖峰,常昊,李鉴林,等.2016.维西—乔后断裂南段正断层活动特征[J].地震研究,39(4):579-586.
常祖峰,张艳凤,周青云,等.2014.2013年洱源MS5.5地震烈度分布及震区活动构造背景研究[J].中国地震,30(4):560-570.
胡鸿翔,陆涵行,王椿镛,等.1986.滇西地区地壳结构的爆破地震研究[J].地球物理学报,29(2):133-144.
姜金钟,陈棋福,李姣.2019.中国东北的深源地震波形匹配检测及定位[J].地球物理学报,62(8):2930-2945.
姜金钟,付虹,陈棋福.2016.位于构造活跃区的小湾水库地震活动特征——基于地震精定位的分析[J].地球物理学报,59(7):2468-2485.
李姣,姜金钟,王光明,等.2021.2018年云南通海MS5.0双震震源机制解及深度测定研究[J].地震研究,44(2):76-87.
李姣,姜金钟,杨晶琼.2020.2017年漾濞MS4.8和MS5.1地震序列的微震检测及重定位[J].地震学报,42(5):527-542.
李涛,付虹,姜金钟,等.2018.2013年云南洱源MS5.5地震序列不同地震观测台网地震定位结果对比分析[J].地震研究,41(1):55-63.
林中洋,胡鸿翔,张文彬,等.1993.滇西地区地壳上地幔速度结构特征的研究[J].地震学报,15(4):427-440.
潘睿,姜金钟,付虹,等.2019.2017年云南漾濞MS5.1及MS4.8地震震源机制解和震源深度测定[J].地震研究,42(3):338-348.
任俊杰,张世民,侯治华,等.2007.滇西北通甸—巍山断裂中段的晚第四纪滑动速率[J].地震地质,29(4):756-764.
王椿镛,Mooney W D,王溪莉,等.2002.川滇地区地壳上地幔三维速度结构研究[J].地震学报,24(1):1-16.
吴建平,明跃红,王椿镛.2004.云南地区中小地震震源机制及构造应力场研究[J].地震学报,26(5):457-465.
姚华建.2020.中国川滇地区公共速度模型构建:思路与进展[J].中国科学:地球科学,50(9):1319-1322.
易桂喜,龙锋,张致伟.2012.汶川MS8.0地震余震震源机制时空分布特征[J].地球物理学报,55(4):1213-1227.
赵小艳,付虹.2014.2013年洱源MS5.5和MS5.0地震发震构造识别[J].地震学报,36(4):640-650.
郑勇,马宏生,吕坚,等.2009.汶川地震强余震(MS≥ 5.6)的震源机制解及其与发震构造[J].中国科学:地球科学,39(4):413-426.
Hardebeck J L.2013.Geometry and earthquake potential of the Shoreline fault,central California[J].Bull Seismol Soc Am,103(1):447-462.
Jiang J,Li J,Fu H.2019.Seismicity analysis of the 2016 MS5.0 Yunlong Earthquake,Yunnan,China and its tectonic implications[J].Pure and Applied Geophysics,176(3),1225-1241.
Liu Y,Yao H J,Zhang H J,et al.2021.The community velocity model V1.0 of southwest China,constructed from joint body-and surface-wave traveltime tomography[J].Seismological Research Letters,92(5):2972-2987.
Waldhauser F,Ellsworth W L.2000.A double difference earthquake location algorithm method and application to the Northern Hayward Fault,California[J].Bulletin of the Seismological Society of America,96(6):1353-1368.
Waldhauser F,Schaff D P.2008.Large-scale relocation of two decades of northern California seismicity using cross-correlation and double-difference methods[J].J Geophys Res:Solid Earth,113(B8):B08311.
Wang X,Wei S,Wu W.2017.Double-ramp on the Main Himalayan Thrust revealed by broadband waveform modeling of the 2015 Gorkha earthquake sequence[J].Earth Planet Sci Lett,473:83-93.
Xin H L,Zhang H J,Kang M,et al.2019.High-resolution lithospheric velocity structure of continental China by double-difference seismic travel-time tomography[J].Seismological Research Letters,90(1):229-241.
Yang Y,Yao H J,Wu H,et al.2020.Crustal shear-velocity model in Southwest China from joint seismological inversion and its implications for regional crustal dynamics[J].Geophys J Int,220(2):1379-1393.
Zhu L P,Helmberger D V.1996.Advancement in source estimation techniques using broadband regional seismograms[J].Bulletin of the Seismological Society of America,86(5):1634-1641.

备注

引言

1 数据选取和研究方法

2 CAP方法反演震源机制解

3 双差地震定位及不确定性分析

4 讨论

5 结论

期刊信息