A mechanism for sustained groundwater pressure changes induced by distant earthquakes
A mechanism for sustained groundwater pressure changes induced by distant earthquakes
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DOI：
10.1029/2002jb002321
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发表时间：
2003-08-22
影响因子：
3.9
通讯作者：
Manga, M
中科院分区：
文献类型：
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作者：
Brodsky, EE;Roeloffs, E;Manga, M
30多年来，远距离(超过数百公里)地震的巨大、持续的井水位变化(>；10厘米)已被证明是一个谜。在这里，我们使用俄勒冈州格兰茨帕斯附近的一口井的高采样率，对水位的动态响应和持续变化或步骤进行第一次同步分析。我们观察到，在突然的同震步骤中，水位振幅与地震波地面速度之比增加了40倍。在此基础上，我们提出了一种新的同震孔压阶跃模型，在该模型中，由地下水流沉积的临时屏障被地震波诱导的更快的水流夹带和移除。在热液区，这种机制可能导致4×10(-2)Mpa的压力变化并触发地震活动。
Large, sustained well water level changes (>10 cm) in response to distant (more than hundreds of kilometers) earthquakes have proven enigmatic for over 30 years. Here we use high sampling rates at a well near Grants Pass, Oregon, to perform the first simultaneous analysis of both the dynamic response of water level and sustained changes, or steps. We observe a factor of 40 increase in the ratio of water level amplitude to seismic wave ground velocity during a sudden coseismic step. On the basis of this observation we propose a new model for coseismic pore pressure steps in which a temporary barrier deposited by groundwater flow is entrained and removed by the more rapid flow induced by the seismic waves. In hydrothermal areas, this mechanism could lead to 4 x 10(-2) MPa pressure changes and triggered seismicity.