Destructive strong ground motion in Mexico city: Source, path, and site effects during great 1985 Michoacán earthquake
Destructive strong ground motion in Mexico city: Source, path, and site effects during great 1985 Michoacán earthquake
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DOI：
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发表时间：
1989-12
影响因子：
3
通讯作者：
M. Campillo;J. Gariel;K. Aki;F. Sánchez-Sesma
中科院分区：
文献类型：
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作者：
M. Campillo;J. Gariel;K. Aki;F. Sánchez-Sesma
在1985年的米霍坎地震中，同时考虑震源、路径和场地对地面运动的影响，使我们能够得出关于墨西哥城地震破裂过程、波在震中区和墨西哥城之间的传播模式以及当地放大作用所起作用的一致结论。相反的水平分量，表现出显着放大的2至3秒的运动在湖泊沉积物的网站，我们观察到几乎相同的垂直位移地震图包含波纹与2至3秒的周期在整个墨西哥城的山谷记录网站是在湖泊沉积物或硬岩石。因此，我们的结论是，2至3秒的动议负责摧毁墨西哥城是目前在事件领域。在进行相位分析后，我们解释的信号的叠加长周期瑞利波和短周期Lg的主导周期约为3秒。对地震记录的分析表明，在3秒左右的波周期中，这次地震的辐射增强。除了怀疑有异常路径效应的台站外，记录显示在信号开始后几秒钟出现波纹。近断层记录的特征表明，破裂过程由光滑裂纹的扩展组成。数值模拟结果表明，3秒周期的脉动可以用破裂前缘速度的一系列变化来解释。我们研究了两个替代源模型与不同的地壳模型来解释在墨西哥城记录的垂直位移的特点。我们的首选模型属性的原因，加强3秒的运动，在破裂传播的不规则性，除了在墨西哥城的当地条件的影响。这种解释导致了一个非常连贯的场景，从断层开始失败到墨西哥城的破坏。这个例子说明，为了理解强地面运动，需要同时考虑震源、路径和场地效应。
Simultaneous consideration of source, path, and site effects on ground motion during the Michoacan earthquake of 1985 allows us to draw coherent conclusions regarding the roles played for the disaster in Mexico City by the rupture process, the mode of propagation of the waves between the epicentral zone and Mexico City, and the local amplification. In contrast to the horizontal component which showed dramatic amplification for the 2 to 3 sec motion at lake sediment sites, we observe almost identical vertical displacement seismograms containing ripples with 2 to 3 sec period throughout the Mexico City valley whether the recording site is on the lake sediments or on hard rock. We, therefore, conclude that the 2 to 3 sec motion responsible for the destruction of Mexico City was present in the incident field. After performing a phase analysis, we interpret the signal as the superposition of long-period Rayleigh waves and short-period Lg with a dominant period of about 3 sec. The analysis of the teleseismic records indicates that the radiation of this event is enhanced for waves around the 3 sec period. Except in the case of stations for which an anomalous path effect is suspected, the records present ripples appearing a few seconds after the beginning of the signal. The characteristics of near-fault records show that the rupture process consists of the growth of a smooth crack. The numerical simulation indicates that the 3 sec period ripples can be explained by a series of changes of the rupture front velocity. We examine two alternative source models associated with different crustal models to explain the characteristics of the vertical displacements recorded in Mexico City. Our preferred model attributes the cause of the enhanced 3 sec motion to the irregularity in the rupture propagation in addition to the effect of the local conditions in Mexico City. This interpretation leads to a very coherent scenario of what happened from the start of the failure on the fault up to the destruction in Mexico City. This example illustrates the need to consider simultaneously source, path, and site effects in order to understand strong ground motions.