Geoelectric potential changes: Possible precursors to earthquakes in Japan
Geoelectric potential changes: Possible precursors to earthquakes in Japan
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DOI：
10.1073/pnas.97.9.4561
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发表时间：
2000-04-25
影响因子：
11.1
通讯作者：
Takahashi, I
中科院分区：
文献类型：
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作者：
Uyeda, S;Nagao, T;Takahashi, I
地震电磁前兆（EQ）是否存在不仅对于地震前兆预测而且对于理解地震前兆物理过程也是一个重要问题。在日本最近的几个 EQ 之前已经观察到缓慢的瞬态地电势变化。在大多数情况下，它们出现在 EQ 之前 1-19 天，其持续时间和强度为几分钟至 1 小时和 1-2 mV/100 m。在观测期间，在我们台站 20 公里范围内发生的所有 6 个震级大于或等于 5 的 EQ 中，有 5 个发生了变化。在另外两个EQ（其中一个震级为4.7级）之前，在更远的震中距离（长达75公里）处也检测到了变化。在此之前，三个相距较远的电台同时记录了一个信号。这些地电势变化已通过以下标准与众多其他变化（各种来源的噪声）区分开来。 (i) 所选变化的幅度与记录站短偶极子（大约 100 m）的长度成正比，并且在长偶极子运行时也在长偶极子（1-10 km）上同时检测到。 (ii) 在观察期内没有发生未采用 EQ 的此类变化。尽管这些地电势变化的 EQ 前兆性质无可否认尚未得到证实，但目前的结果似乎值得继续认真研究这些信号的发生、产生和传输及其与 EQ 可能的因果关系。
Whether electromagnetic precursors to earthquakes (EQs) exist is an important question not only for EQ prediction but also for understanding the physical processes of EQ generation. Slow transient geoelectric potential changes have been observed before several recent EQs in Japan. In most cases, they appeared 1-19 days before the EQs, and their duration and intensity were several minutes to 1 h and 1-2 mV/100 m. The changes appeared before five of all six EQs with magnitude greater than or equal to 5 that occurred within 20 km of our stations during the observation period. Changes were also detected at greater epicentral distances (up to 75 km) before two other EQs, including one EQ of magnitude 4.7. which was preceded by a signal simultaneously recorded at three widely separated stations. These geoelectric potential changes have been distinguished through the following criteria from a multitude of other changes, which were noise of various origins. (i) The selected changes were proportional in amplitude to the length of the recording station's short (approximate to 100 m) dipoles and were simultaneously detected also on long (1-10 km) dipoles when the latter were in operation. (ii) No such changes occurred during the observation period that were not followed by EQs. Although the EQ precursory nature of these geoelectric potential changes is admittedly unproven, it seems that the present results warrant continued serious research into the occurrence, generation, and transmission of these signals and their possible causal relationship to EQs.