著者

尾池 和夫 村上 寛史

出版者

独立行政法人防災科学技術研究所

雑誌

防災科学技術研究所研究資料 (ISSN:0917057X)

巻号頁・発行日

vol.157, pp.221-251, 1993-03-29

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Continuous observations of variation of the number of LF and VLF electromagnetic noises have been done at the Uji station in Kyoto Prefecture. LF noise is observed by CRF-1 type radio receiver whose frequency is fixed at 163kHz and VLF noise is observed by ball antenna with band-pass filter from 1 to 10kHz. The temporal variation of the number of LF and VLF noises has been compared with the occurrence of near shallow earthquakes. In the case of 70 per cent of large earthquakes with magnitude larger than or equal to 6.0 anomalous increase of LF noises is observed within one day before the main shock whose epicentres are located in the land or shallow sea region. Similar phenomena are found in the case of near shallow earthquakes with magnitude larger than or equal to 5.0. Present study indicates the possibility of the existence of certain kinds of physical relationship between the occurrence of shallow earthquakes and LF and VLF electromagnetic noises.