Relationship Between Seismic Electric Signals and Tectonics Derived from Dense Geoelectric Observations in Taiwan
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Some researchers have suggested that significant electromagnetic changes that can be detected prior to strong earthquakes are associated with the tectonics and subsurface structures beneath monitoring stations. Numerical simulation seems to support this phenomenon. However, to date, few field measurement data are available to address this issue. In this work, we used the shifting correlation method to analyze 2-month recordings of 20 geoelectric stations in Taiwan and found at least two stations had recorded geoelectric signals significantly correlated with known seismic events. These two stations are installed on large reverse faults, which are probably characterized by high stress concentrations before earthquakes. In addition, they share the same resistivity variation pattern, namely, a conductor layer sandwiched between two high-resistivity layers. Moreover, both stations are above the electrical resistivity boundaries, which means they have an increased probability of recording the abnormal disturbance once EM signals have been emitted from EQs. Our analysis results support the viewpoint that lateral and vertical electrical resistivity variation and conductors in the subsurface may be able to amplify seismic electric signals.
KeywordsStatistical seismology seismic electric signals shifting correlation method tectonics and deep structures in Taiwan
We would like to express sincere appreciation to the anonymous reviewers whose comments are important to improving our manuscript. This research was supported by the Natural Science Foundation of China (no. 41574066) as well as grants from the State Key Laboratory of Earthquake Dynamics of China. The first author, Feng Jiang, did all the specific data processing and analysis, figure making, paper writing and editing. The main idea described in this article was proposed by the corresponding author, Xiaobin Chen, and he is also advisor to the first author. The third and fourth authors provided all the original data and made some comments. We thank PhD student Benjamin Lee of the University of Alberta for his time spent correcting the language mistakes in the original paper and making some comments to improve this paper. We appreciate Prof. Martyn Unsworth and his former student Ted Bertrand of the University of Alberta who provided all the 2D and 3D MT inversion models for this article. We thank Prof. Xianglin Gao for reading and polishing the language. All the data used are listed in the references, tables and supplements. Some other detailed information about the data is provided in the supporting information.
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