缅甸弧强震对川滇地区主要断裂的应力影响*

(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)

缅甸弧; 发震机制; 累积库仑应力; 川滇地区

Stress Influence on Major Faults in the Sichuan-Yunnan Region by Strong Earthquakes near the Burma Arc
ZANG Yang1,2,HAN Yanyan2,MENG Lingyuan2

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

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

备注

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.