1973年炉霍大地震(M_S=7.6)最大余震(M_S=6.3)的库仑破裂应力触发

The Triggering Mechanism of the Largest Aftershock (M_S=6.3) of the 1973 Luhuo Great Earthquake (M_S=7.6)

1973年 2月 6日在四川省炉霍发生MS7 6大地震 ,震后在震中周围出现丰富的余震 ,其最大余震 (MS6 3)发生在鲜水河断裂和玉树 -甘孜断裂之间的正断层活动区内。本文根据震源机制解、地表破裂、同震位错分布、地震地质构造等资料 ,建立炉霍走滑大地震破裂的弹性位错模型 ,计算该大地震在周围正断层滑动方向上引起的库仑破裂应力变化 (ΔCFS)。结果表明 ,最大余震发生在库仑破裂应力增加 (ΔCFS >0 )的地区 ,ΔCFS =4 5MPa。因此认为 ,最大余震可能是由主震引起的库仑破裂应力变化触发的。

The Luhuo great earthquake (M S=7.6) occurred on Feb.7, 1973 in Sichuan Province.There were a lot of aftershocks in the source area.The largest aftershock (M S=6.3) occurred in the normal fault zone between the Xianshuihe fault and the Ganzi-Yushu fault.Based on the source resolution,surface rupture,coseismic dislocation and seismic geological structure data,an elastic dislocation model of the Luhuo great earthquake with strike slip mechanism is designed and the Coulomb failure stress change (ΔCFS) in the slip direction on the normal faults in and around the source zone due to the great earthquake is calculated.The results show that the largest aftershock occurred in an area with ΔCFS>0,ΔCFS=4.5MPa.Therefore,the largest aftershock was probably triggered by the Coulomb failure stress change.