2014年四川康定双震震源的勒夫波分析

2014年11月22日在四川省康定县发生了MS6.3地震(M1),3天后几乎在同一地点又发生了MS5.8地震(M2),本文称其为"康定双震".首先,利用逆时成像技术对康定双震以及用作经验格林函数事件的一次ML4.8地震(G1)进行了重定位,并利用广义极性振幅技术反演了三次地震的震源机制;然后,借助于G1的记录,利用经验格林函数技术分别提取了M1和M2的勒夫波视震源时间函数,并利用视震源时间函数的方位依赖性分析了M1和M2的优势破裂方向;最后,利用视震源时间函数反演方法反演了M1和M2的震源破裂过程.重定位结果表明,G1与M1和M2震源位置比较接近,分别相距~40 km和~50 km.震源机制反演结果表明,G1与M1和M2具有类似的机制,均为陡倾角左旋走滑.视震源时间函数的方向性分析表明,M1的破裂优势方向为276°,而M2的破裂优势方向为336°.破裂过程反演结果表明,M1持续时间~11 s,主要破裂区沿断层面朝北西以及浅表拓展,最大位错~0.52 m;M2持续时间~7 s,破裂区沿着断层面也朝北西以及浅部拓展,最大位错~0.33 m.

Analysis of the Love-waves for the rupture processes of the 2014 earthquake-doublet of Kangding,Sichuan

An M_S6.3 earthquake (M1) struck Kangding county in Sichuan province on 22 November 2014. Three days later, another M_S5.8 earthquake (M2) occurred in almost the same area. Both together are called "Kangding earthquake-doublet" here. Firstly, we used the time-reversal imaging technique to relocate the doublet and an M_L4.8 earthquake (G1) which was used as the empirical Green's function event, and then we used the generalized polarity and amplitude technique to invert for their focal mechanisms. Secondly, we retrieved the Apparent Source Time Functions (ASTFs) of the M1 and M2 with the G1 using the empirical Green's function technique, and analyzed their dominant rupture directions with the azimuth-dependent ASTFs. Lastly, we obtained the spatial-temporal rupture processes of the M1 and M2 by inverting the ASTFs. The relocation results show that the G1 is fairly but not very close to the M1 and M2, ~40 km and ~50 km apart, respectively. The inverted focal mechanism results show that the G1 is similar to the M1 and M2, respectively, in focal mechanism, being steep-dip left-lateral strike-slip events. The analysis of the ASTFs' azimuth-dependence suggests that the dominant rupture direction of the M1 is 276° while that of the M2 is 336°. The inverted rupture processes indicate that the M1 lasted ~11 s, and its main rupture propagated toward NW and to ground surface, resulting in a maximal slip of ~0.52 m; the M2 lasted ~7 s, and its rupture propagated toward NW and toward ground surface, resulting in a maximal slip of ~0.33 m.