摘要
2018年1月23日,在美国阿拉斯加湾海域发生了一次MW7.9地震.震源机制解表明这次地震以走滑为主,可能发生在近东西向或南北向的陡倾角断层上,早期余震并非线型展布.我们利用视震源时间函数分析确定了此次地震的总体破裂方向,并结合余震的空间展布特征构建了相互交叉的双断层模型,进而通过联合反演远场P波和SH波数据获得了此次地震的时空破裂过程.视震源时间函数分析表明总体破裂方向既非东西也非南北,而且反演结果表明,两个断层上都发生了错动,总体破裂时间～50s,释放标量地震矩～8.11×1020 Nm.震源时间函数表现出多事件特征,且两个断层破裂的时间过程也不相同.破裂首先在南北向断层的南端开始,很快触发了东西向断层,最后终止于南北向断层的北端.每个断层都具有相当的时空复杂性,位错分布很不均匀.东西向断层具有三个凹凸体,一个位于震源附近,其他两个位于断层两端.南北向断层有两个凹凸体,均位于断层北段,最大滑动量～5.0m就出现在这里.发生最大位错的南北向断层延伸至阿拉斯加海沟,增加了触发阿拉斯加海沟其他断层发生破裂的可能性.
On January 23, 2018, an M W7.9 earthquake occurred in the Gulf of Alaska, USA. As the inverted focal mechanism solution suggests, the event was mainly of strike-slip on steep faults which may run nearly from east to west or from north to south (the N-S fault and E-W fault). The early aftershocks don′t appear to be along a straight line. In this study, we determine the overall rupture direction by analyzing the apparent source time functions (ASTFs), and then, combining the direction with the pattern of the aftershocks, we build a double-fault model, with one crossing with the other, and obtain the tempo-spatial process by jointly inverting the P and SH waveform data. The analysis of the ASTFs shows that the overall rupture direction is neither north-to-south nor east-to-west, and the inverted results show, the two faults participate in the event, with a total duration of ~50 s and a moment release of ~8.11×10^20 Nm. Multi-events can be recognized on the inverted source time function, and the two faults have different temporal processes. The rupture starts on southern end of the N-S fault, soon propagates on the E-W fault, and finally stops on northern end of the N-S fault. Each of the faults has quite tempo-spatial complexity, with highly heterogeneous slip on each of them. There are three slip asperities on the E-W fault, with one near the hypocenter while the others on two ends of the fault. There are two slip asperities on the N-S fault, with both of them on the northern end. Right here appears the maximal slip ~5.0 m. The N-S fault stretches into the Gulf of Alaska, so the probability that other faults in this gulf are triggered is believed to have increased.
作者
张旭
许力生
杜海林
易磊
ZHANG Xu;XU LiSheng;DU HaiLin;YI Lei(Institute of Geophysics, China Earthquake Administration, Beijing 100081, China;Key Laboratory of Comprehensive and Highly Efficient Utilization of Salt Lake Resources, Qinghai Institute of Salt Lakes, Chinese Academy of Sciences, Xining 810008, China;Qinghai Provincial Key Laboratory of Geology and Environment of Salt Lakes, Qinghai Institute of Salt Lakes, Chinese Academy of Sciences, Xining 810008, China)
出处
《地球物理学报》
SCIE
EI
CAS
CSCD
北大核心
2019年第5期1680-1692,共13页
Chinese Journal of Geophysics
基金
科技部国家重点研发计划(2018YFC1503400)
中国地震局地球物理研究所基本业务费(DQJB19B08)联合资助
