地殻活動に伴うELF/VLF帯電磁放射現象の研究

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Main purpose of this study is to clarify characteristics of the electromagnetic radiation associated with earth's crustal activities in order to search for a new technique for prediction of earthquake or volcanic eruption. Since 1985 a large amount of continuous records of natural electromagnetic noises in ELF/VLF bands (10 Hz-32 kHz) have been obtained at Kochi, Southwest Japan. This observation has been conducted under the Stanford University ELF/VLF Radiometer Project that has a purpose to research into global distribution of natural electromagnetic noises. We analyzed the records at Kochi especially in connection with local seismic activities. We investigated the relationship between anomalous electromagnetic noises and major earthquakes occurred in and around Southwest Japan during the past five years. Though clear precursory electromagnetic radiation was not detected, anomalous abrupt increase of noise level was sometimes observed synchronously with the ground motion of felt earthquake. This change is more remarkable in a lower frequency band, and is probably caused by antenna shaking generated by seismic ground motion. Alternative interpretation is that seismic ground motion induces very local electromagnetic radiation from surrounding rocks in the vicinity of antenna site. It has become clear that the present Radiometer recording system unfortunately does not provide sufficient information concerning propagation direction or characteristics of original wave form because of the limit of recording capacity. To compensate for it we have made a continuous recording system for both North-South and East-West components of ELF signals using a Digital Audio Tape with a huge recording capacity. Further observation with a new recording system is now undertaken.
独立行政法人防災科学技術研究所の論文
1995-03-31

地殻活動に伴うELF/VLF帯電磁放射現象の研究

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