地震研究

云南地震活动与周边强震存在“构造相连,动力同源”的特征,研究周边强震的序列演化特征及发震构造,对云南地区地震研究具有重要意义。2021年12月24日老挝M_S6.0地震发生在滇西南地区的NW向整董断裂附近,震源机制解显示,此次地震是一次走滑型破裂事件,破裂方向与区域构造特征一致。老挝M_S6.0地震序列属于前震-主震-余震型序列,主震前震中附近出现3～4级地震非常活跃的现象,前震序列参数计算显示b值波动相对幅度较大,h值出现“上翘”形态,而余震序列b值和h值变化均相对平稳,主震的同震库伦应力结果表明老挝地震可能对云南地区有应力加载作用。

The seismicity in Yunnan is related with the strong earthquake activities in its surrounding areas because of their “joint structures and homologic driving forces” .So,study of the earthquake evolution and the seismogenic structures in the vicinity will help predict the earthquakes in Yunnan.On November 24,2021,the Laos M_S6.0 earthquake occurred near the Zhengdong fault in Southwest Yunnan.Its focal mechanism reveals that the earthquake is a strike-slip fracture event.The rupture extends in consistent with the regional tectonic trend.The Laos M_S6.0 earthquake sequence is a typical foreshock-mainshock-aftershock sequence.The foreshock sequence has abundant M_S3.0 and M_S4.0 earthquakes.According to the parameters of the foreshock sequence,before the main shock the calculated b-value fluctuates with large amplitude,and h-value has an upward trend.On the other hand,in the aftershock sequence,variation of b-value and h-value is relatively stable.In addition,the coseismic Coulomb stress caused by the M_S6.0 mainshock may have a stress-loading effect on Yunnan region.

引言
1 构造背景与历史地震
2 震源参数
3 老挝M_S6.0地震序列分析
4 结论

图1 老挝MS6.0地震震区地质构造简图<br/>Fig.1 Geological settings in the Laos MS6.0 earthquake region

图1 老挝MS6.0地震震区地质构造简图
Fig.1 Geological settings in the Laos MS6.0 earthquake region

图2 老挝MS6.0地震周边地区历史地震和测震台站分布<br/>Fig.2 Historical earthquakes and digital seismic stations around the Laos MS6.0 earthquake area

图2 老挝MS6.0地震周边地区历史地震和测震台站分布
Fig.2 Historical earthquakes and digital seismic stations around the Laos MS6.0 earthquake area

表1 不同机构给出的老挝MS6.0地震震源参数<br/>Tab.1 Focal parameters of the Laos MS6.0 earthquake given by different institutions

表1 不同机构给出的老挝MS6.0地震震源参数
Tab.1 Focal parameters of the Laos MS6.0 earthquake given by different institutions

表2 不同机构给出的老挝MS6.0地震断层面解<br/>Tab.2 Fault plane solutions of the Laos MS6.0 earthquake given by different institutions

表2 不同机构给出的老挝MS6.0地震断层面解
Tab.2 Fault plane solutions of the Laos MS6.0 earthquake given by different institutions

图3 云南地震台(a)、中国地震台网中心(b)、NEIC(c)和GCMT(d)计算得到老挝MS6.0地震震源机制解<br/>Fig.3 The focal mechanism solutions for the Laos MS6.0 earthquake given by Yunnan Earthquake Station (a),CENC(b),NEIC(c),and GCMT(d)

图3 云南地震台(a)、中国地震台网中心(b)、NEIC(c)和GCMT(d)计算得到老挝MS6.0地震震源机制解
Fig.3 The focal mechanism solutions for the Laos MS6.0 earthquake given by Yunnan Earthquake Station (a),CENC(b),NEIC(c),and GCMT(d)

表3 老挝MS6.0地震序列中ML≥4.0地震<br/>Tab.3 ML≥4.0 earthquakes in the Laos MS6.0 earthquake sequence

表3 老挝MS6.0地震序列中ML≥4.0地震
Tab.3 ML≥4.0 earthquakes in the Laos MS6.0 earthquake sequence

图4 老挝MS6.0地震序列中ML≥1.0地震M-t图(a)和N-t图(b)<br/>Fig.4 Time history of the Laos MS6.0 earthquake sequence:M-t graph(a)and N-t graph(b) of the ML≥1.0 earthquakes

图4 老挝MS6.0地震序列中ML≥1.0地震M-t图(a)和N-t图(b)
Fig.4 Time history of the Laos MS6.0 earthquake sequence:M-t graph(a)and N-t graph(b) of the ML≥1.0 earthquakes

图5 老挝MS6.0地震序列不同阶段地震震中分布图<br/>Fig.5 Distribution of the epicenters in different stages of the Laos MS6.0 earthquake sequence

图5 老挝MS6.0地震序列不同阶段地震震中分布图
Fig.5 Distribution of the epicenters in different stages of the Laos MS6.0 earthquake sequence

图6 老挝MS6.0地震同震库仑应力变化<br/>Fig.6 Coseismic Coulomb stress changes caused by the Laos MS6.0 earthquake

图6 老挝MS6.0地震同震库仑应力变化
Fig.6 Coseismic Coulomb stress changes caused by the Laos MS6.0 earthquake

图7 老挝MS6.0地震序列震中重定位分布图<br/>Fig.7 Epicentral distribution of the Laos MS6.0 earthquake sequence after relocation

图7 老挝MS6.0地震序列震中重定位分布图
Fig.7 Epicentral distribution of the Laos MS6.0 earthquake sequence after relocation

图8 老挝MS6.0地震后24小时内地震的震级-累计频度分布<br/>Fig.8 Magnitude vs cumulative frequency within 24 hours after the Laos MS6.0 mainshock

图8 老挝MS6.0地震后24小时内地震的震级-累计频度分布
Fig.8 Magnitude vs cumulative frequency within 24 hours after the Laos MS6.0 mainshock

图9 老挝MS6.0地震序列b值(a)及其周边200 km范围区域背景b值时序图(b)<br/>Fig.9 Time history of the b-value of the Laos MS6.0 earthquake sequence(a)and the time history of the b-value of the historical earthquakes within 200 km around the Laos MS6.0 earthquake sequence(b)

图9 老挝MS6.0地震序列b值(a)及其周边200 km范围区域背景b值时序图(b)
Fig.9 Time history of the b-value of the Laos MS6.0 earthquake sequence(a)and the time history of the b-value of the historical earthquakes within 200 km around the Laos MS6.0 earthquake sequence(b)

图10 老挝MS6.0地震序列前震序列(a)和余震序列(b)h值计算结果<br/>Fig.10 The calculated h-value of the foreshock sequence(a)and the aftershock sequence(b) of the Laos MS6.0 earthquake sequence

图10 老挝MS6.0地震序列前震序列(a)和余震序列(b)h值计算结果
Fig.10 The calculated h-value of the foreshock sequence(a)and the aftershock sequence(b) of the Laos MS6.0 earthquake sequence

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备注

引言

1 构造背景与历史地震

2 震源参数

3 老挝M_S6.0地震序列分析

4 结论

期刊信息

备注

引言

1 构造背景与历史地震

2 震源参数

3 老挝MS6.0地震序列分析

4 结论

期刊信息

3 老挝M_S6.0地震序列分析