地震研究

缅甸弧强震对川滇地区主要断裂的应力影响^*

臧阳^1,2,韩颜颜²,孟令媛²

(1.中国地震局地球物理研究所,北京 100081; 2.中国地震台网中心,北京 100045)

Stress Influence on Major Faults in the Sichuan-Yunnan Region by Strong Earthquakes near the Burma Arc

ZANG Yang^1,2,HAN Yanyan²,MENG Lingyuan²

(1.Institute of Geophysics,China Earthquake Adminsitration,Beijing,100081,China)(2.China Earthquake Networks Center,Beijing 100045,China)

Keywords：Burma arc; seismogenic mechanism; cumulative coulomb stress; Sichuan-Yunnan region

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参考文献

收集并分析了1969—2018年缅甸弧地区共170次地震的震源机制解,发现浅源地震主要分布在缅甸弧西侧和实皆断裂,且震源机制解以走滑为主; 逆冲型地震主要位于缅甸弧中部,且以中源地震为主; 正断型地震主要分布在缅甸弧南侧。基于缅甸弧至川滇地区粘弹性介质模型,以川滇地区51条主要断裂、129个断层段、2 112个断层离散点作为接收断层模型,分别计算了缅甸弧单次地震模型和1969—2018年所有MW≥6.0地震在川滇地区产生的静态和累积库仑应力。结果表明:缅甸弧中源地震对川滇地区库仑应力影响较小,一般情况下可忽略不计; 浅源地震在川滇地区产生的库仑应力大小明显高于中源地震; 1969—2018年缅甸弧所有MW≥6.0地震对川滇地区的最大累积库仑应力小于0.1 bar,应力加载作用最强的区域集中在小滇西—滇西北附近地区。[JP]

After collecting and analyzing the focal mechanism solutions of 170 earthquakes from 1969 to 2018 near the Burma arc,we found that the shallow earthquakes are mainly distributed on the Sagaing Fault and in the western part of the Burma arc,usually with a strike-slip mechanism solution. The thrust earthquakes are mainly distributed in the central Burma arc and usually are intermediate earthquakes. While the normal earthquakes mainly distributed in the southern part of the Burma arc. We established the viscoelastic model from the Burma arc to the Sichuan-Yunnan region and using 2 112 discrete points from 129 fault segments of 51 main faults in the Sichuan-Yunnan region as the receiving fault model,then calculated static and cumulative coulomb stress generated by single earthquake model,shallow and intermediate MW≥6.0 earthquakes near the Burma arc from 1969 to 2018,respectively. The results show that the coulomb stress influence in the Sichuan-Yunnan region generated by intermediate earthquakes near the Burma arc is limited,generally negligible. The coulomb stress in the Sichuan-Yunnan region generated by shallow earthquakes is much greater than caused by intermediate earthquakes near the Burma arc. The total cumulative coulomb stress in the Sichuan-Yunnan region generated by all of the MW≥6.0 earthquakes near the Burma arc from 1969 to 2018 is less than 0.1 bar,and the strongest stress loading area concentrated in the region from Xiaodianxi to northwest of Yunnan.

引言
1 方法、数据及模型参数选取
2 缅甸弧地区震源机制特征及中源地震的破裂机制
3 库仑应力计算结果及分析
4 缅甸弧中源地震与川滇地区强震统计关系
5 结论及讨论

表1 1969—2018年缅甸弧地区MW≥6.0地震信息<br/>Tab.1 Information of MW≥6.0 events near Burma arc from 1969 to 2018

表1 1969—2018年缅甸弧地区MW≥6.0地震信息
Tab.1 Information of MW≥6.0 events near Burma arc from 1969 to 2018

图1 1969—2018年缅甸弧地区MW≥4.7地震震源深度分布图<br/>Fig.1 Distribution of MW≥4.7 events along depth near Burma arc from 1969 to 2018

图1 1969—2018年缅甸弧地区MW≥4.7地震震源深度分布图
Fig.1 Distribution of MW≥4.7 events along depth near Burma arc from 1969 to 2018

表2 研究区介质模型参数<br/>Tab.2 Model parameters of the underground medium in the study area

表2 研究区介质模型参数
Tab.2 Model parameters of the underground medium in the study area

图2 缅甸弧地区MW≥5.0(a)、MW≥6.0(b)地震震源机制解<br/>Fig.2 Focal mechanism solutions of MW≥5.0 earthquakes(a),and MW≥6.0 earthquakes(b)near the Burma arc

图2 缅甸弧地区MW≥5.0(a)、MW≥6.0(b)地震震源机制解
Fig.2 Focal mechanism solutions of MW≥5.0 earthquakes(a),and MW≥6.0 earthquakes(b)near the Burma arc

图3 缅甸弧地区MW≥5.0地震震源机制解随震源深度和纬度分布<br/>Fig.3 Distribution of mechanism solutions of MW≥5.0 events along depth and latitude near the Burma arc

图3 缅甸弧地区MW≥5.0地震震源机制解随震源深度和纬度分布
Fig.3 Distribution of mechanism solutions of MW≥5.0 events along depth and latitude near the Burma arc

图4 缅甸弧俯冲带边界及单元板片俯冲方向在水平面的投影(a)和不同纬度范围中源地震断裂面走向比例分布图(b)<br/>Fig.4 Boundary of the Burma arc subduction zone and unit plate subduction direction(a)and ratio distribution of strikes on rupture surface of intermediate earthquakes in regions of different latitude(b)

图4 缅甸弧俯冲带边界及单元板片俯冲方向在水平面的投影(a)和不同纬度范围中源地震断裂面走向比例分布图(b)
Fig.4 Boundary of the Burma arc subduction zone and unit plate subduction direction(a)and ratio distribution of strikes on rupture surface of intermediate earthquakes in regions of different latitude(b)

表3 地震模型震源参数<br/>Tab.3 Source parameters of the earthquake models

表3 地震模型震源参数
Tab.3 Source parameters of the earthquake models

图5 1号(a),2号(b),3号(c)和4号(d)地震模型对川滇地区主要断裂同震库仑应力计算结果<br/>Fig.5 Results of coseismic coulomb stress generated by No.1(a),No.2(b),No.3(c),and No.4(d)earthquake model on main faults in the Sichuan-Yunnan region

图5 1号(a),2号(b),3号(c)和4号(d)地震模型对川滇地区主要断裂同震库仑应力计算结果
Fig.5 Results of coseismic coulomb stress generated by No.1(a),No.2(b),No.3(c),and No.4(d)earthquake model on main faults in the Sichuan-Yunnan region

图6 缅甸弧地区中源强震对川滇地区主要断裂累积库仑应力时间进程(以9次中源地震发生后第1天及2018年12月31日作为时间切片)<br/>Fig.6 Temporal evolution of cumulative coulomb stress in the Sichuan-Yunnan region generated by intermediate strong earthquakes occurred near the Burma arc(using first days after 9 intermediate earthquakes and Dec.31,2018 as time slices)

图6 缅甸弧地区中源强震对川滇地区主要断裂累积库仑应力时间进程(以9次中源地震发生后第1天及2018年12月31日作为时间切片)
Fig.6 Temporal evolution of cumulative coulomb stress in the Sichuan-Yunnan region generated by intermediate strong earthquakes occurred near the Burma arc(using first days after 9 intermediate earthquakes and Dec.31,2018 as time slices)

图7 缅甸弧地区浅源强震对川滇地区主要断裂累积库仑应力时间进程(以9次浅源地震发生后第1天及2018年12月31日作为时间切片)<br/>Fig.7 Temporal evolution of cumulative coulomb stress in the Sichuan-Yunnan region generated by shallow strong earthquakes occurred near the Burma arc(using first days after 9 shallow earthquakes and Dec.31,2018 as time slices)

图7 缅甸弧地区浅源强震对川滇地区主要断裂累积库仑应力时间进程(以9次浅源地震发生后第1天及2018年12月31日作为时间切片)
Fig.7 Temporal evolution of cumulative coulomb stress in the Sichuan-Yunnan region generated by shallow strong earthquakes occurred near the Burma arc(using first days after 9 shallow earthquakes and Dec.31,2018 as time slices)

图8 1969—2018年缅甸弧地区所有MW≥6.0强震对川滇地区主要断裂累积库仑应力计算结果(截至2018年12月31日)<br/>Fig.8 Cumulative coulomb stress in the Sichuan-Yunnan region generated by all of the MW≥6.0 earthquakes occurred near the Burma arc from 1969 to 2018(up to Dec.31,2018)

图8 1969—2018年缅甸弧地区所有MW≥6.0强震对川滇地区主要断裂累积库仑应力计算结果(截至2018年12月31日)
Fig.8 Cumulative coulomb stress in the Sichuan-Yunnan region generated by all of the MW≥6.0 earthquakes occurred near the Burma arc from 1969 to 2018(up to Dec.31,2018)

图9 1900—2018年缅甸弧附近MS≥7.0中源地震与后续2年内川滇地区MS≥6.0地震统计关系<br/>Fig.9 Statistical relationship between intermediateMS≥7.0 earthquakes near Burma arc and the MS≥6.0 earthquakes in the Sichuan-Yunnan region occurred within the subsequent 2 years from 1900 to 2018

图9 1900—2018年缅甸弧附近MS≥7.0中源地震与后续2年内川滇地区MS≥6.0地震统计关系
Fig.9 Statistical relationship between intermediateMS≥7.0 earthquakes near Burma arc and the MS≥6.0 earthquakes in the Sichuan-Yunnan region occurred within the subsequent 2 years from 1900 to 2018