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特大地震的同震及震后滑动能引起地壳介质的时间变化,这是因为强地面震动破坏了近地表的沉积层,或者应力扰动改变了裂隙密度和/或深部流体的移动。这种随时间变化的地壳属性可引起地震波速度出现部分变化,并可根据互相关波形和测量重复地震序列内它们的时间滞后探测到。本文根据2004年苏门答腊—安达曼特大地震和2005年尼亚斯—锡默卢特大地震的重复余震序列,分析了高频(0.5~2.0Hz)P尾波和S尾波以及长周期(0.03~0.1Hz)面波的滞后时间。观测到的滞后时间揭示出几个主要特征:(1)2004年地震序列的S尾波滞后时间系列!(t)基本上在0值附近波动,有时随消逝时间而变为负值,而2005年地震序列的S尾波的!(t)则表现为随消逝时间而单调增长;(2)S尾波的平均速度降低(-δV S)是P尾波平均速度降低(-δV P)的2倍,瑞利波的平均速度降低(-δV LR)比勒夫波的平均速度降低(-δV LQ)大3~4倍;(3)δV S和δV LR显示了速度随时间的恢复,特别是2005年地震的序列。2005年地震序列δV S速度随时间恢复的形状与附近大地测量台站得到的位移时间系列类似。尽管我们讨论了可能的人为结果,如震源间距、噪声场的时间变化和仪器响应,但观测结果均表明地壳内的非均匀波速时间降低是由2004年和2005年的特大地震的同震和/或震后滑动引起的。
The coseismic and post-earthquake slippage of very large earthquakes can cause temporal changes in the crustal medium because strong ground shaking destroys sub-surface sediments or stress disturbances alter the fracture density and / or the movement of deep fluids. This time-varying crustal property can cause some changes in seismic velocity and can be detected based on cross-correlation waveforms and their time lag within repeated seismic sequences. Based on the repetitive aftershock sequences of the 2004 Sumatra-Andaman Earthquake and the Nias-Silme Lutter Earthquake in 2005, the paper analyzes the P-wave and S-coda waves at high frequencies (0.5-2.0 Hz) and the long-period 0.1Hz) Surface wave lag time. The observed lag time reveals several major features: (1) The series of S-wave lag time series (t) of the 2004 earthquake sequence fluctuates substantially around the value of zero, sometimes becoming negative as the elapsed time, and 2005 (T) of the annual earthquake sequence appears monotonically increasing with the lapse of time; (2) the average velocity of the S-coda (-δV S) is the decrease of the average velocity of the c-wave (-δV P) 2 times, the average velocity of Rayleigh wave (-δV LR) is 3 ~ 4 times lower than the average velocity of -δV LQ in Bereaves wave; (3) δV S and δV LR show the recovery of velocity with time, Especially the sequence of the 2005 earthquake. The shape of the δV S velocity recovered from the 2005 earthquake sequence over time is similar to the series of displacements obtained from nearby geodetic stations. Although we discussed possible artifacts such as source spacing, time variation of noise field and instrumental response, the observations indicate that the reduction of non-uniform wave velocity time in the crust is caused by the coseismic and / Or after the slide caused by the earthquake.