智利Mw8.8地震重力变化的GRACE观测与构造活动分析

摘要

利用GRACE重力卫星数据获取智利地区长期重力变化,提取特征点重力变化时间序列,分析2010年智利Mw8.8地震震前、同震及震后的重力变化,并将GRACE观测到的同震重力变化与球体位错理论模拟结果进行对比分析.结果表明,地震造成发震断层上、下盘显著的重力正负变化;特征点重力变化时序均清晰地揭示出地震造成的重力变化跃迁现象及震后3个强余震的异常信号,特别是震源域特征点重力在地震前2007～2010年呈现出“减小-增加-减小-增加-发震”的变化特征;GRACE观测到的同震重力变化与球体位错理论模拟结果在量级和分布形态上具有较好的一致性;地震不同阶段发震断层两盘重力变化亦有所差异,且受震后地层粘滞性效应影响,发震断层邻域重力变化呈持续性正负变化趋势.%The long-term gravity changes of the Chile region are obtained by GRACE gravity satellite data.The gravity changes before and after the 2010 Mw8.8 Chile earthquake are further analyzed through the time-series of gravity changes of typical points.Finally,the coseismic gravity changes detected by GRACE are compared with the results calculated by the spherical dislocation model.The results show that the strong earthquake caused significant positive and negative gravity changes between the upper wall and foot wall of the seismogenic fault.The time-series of the gravity changes of typical points all clearly reveal the jumping phenomenon caused by the strong earthquake,as well as the abnormal signals caused by the three strong aftershocks.Especially,the gravity changes of a typical point in the epicenter area presents characteristics of "decrease-increase-decrease-increase-earthquake occurrence" from 2007 to 2010 before the strong earthquake.The magnitude and distribution of coseismic gravity changes observed by GRACE are in good agreement with the results calculated by the spherical dislocation model.In the different stages of the earthquake,the gravity changes between the two sides of seismogenic faults are also different.In addition,because of the effect of stratum viscosity after the strong earthquake,the gravity changes around the seismogenic faults will continue to show the trend of positive and negative changes.