2016年日本熊本地震破裂时空过程联合反演

Joint inversion of teleseismic and co-seismic In SAR data for the rupture process of the 2016 Kumamoto earthquake in Japan

为了深入认识2016年4月15日日本熊本地震破裂的复杂性,利用远场体波资料和同震InSAR资料联合反演了此次地震的震源破裂时空过程.联合反演结果表明:熊本地震的震源破裂持续时间约为25 s,整个破裂过程释放的总标量矩为6.03×10^(19) N·m,对应于矩震级M_W7.1;同震滑动主要集中分布于浅部,破裂以右旋走滑为主,但在沿倾向0—5 km范围内,破裂呈较强的正断特征;此次地震破裂的最大同震滑动量约为4.9 m,且最大同震位错区位于背离断层走向上、距离起始破裂点约5—10 km的区域;破裂前期(0—7 s),在倾向上向浅表发生破裂,在走向上向东北和西南两侧扩展;大约7 s后,破裂背离断层走向主要向东北方向扩展.根据有限断层联合反演结果推测,此次熊本地震破裂可能出露至地表.

On April 15,2016,a disastrous earthquake struck Kumamoto county in Japan.Aiming to further understand the complexity of the earthquake rupture in detail,we conduct a joint inversion of teleseismic waveforms and co-seismic In SAR data for the spatio-temporal rupture process of this earthquake. The results show that,the whole process lasted for about 25 s and released scalar moment up to 6.03×1019 N·m,corresponding to moment magnitude MW7.1. The major co-seismic slip distribution was centered in shallow region,and it was dominated by dextral strike. But the rupture had strong normal characteristics in the range of 0-5 km along the dip direction. The maximum co-seismic slip is about 4.9 m,and the major rupture patch was about 5-10 km away from the initial rupture point opposite to the strike direction. In the early stage（0-7 s）,it ruptured toward to the shallow region along the dip direction,and ruptured bilaterally along strike direction; about 7 s later,it ruptured toward to the northeast opposite to the strike direction. The joint inversion results suggest that the Kumamoto earthquake may rupture to the earth surface.