著者

Y. Sue

出版者

Society of Atmospheric Electricity of Japan

雑誌

Journal of Atmospheric Electricity (ISSN:09192050)

巻号頁・発行日

vol.29, no.1, pp.53-62, 2009 (Released:2010-07-09)

参考文献数

9

被引用文献数

2 1

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The question of whether earth tides trigger earthquakes has been the subject of debate for years. Recent studies, at last, have proven the significance of the earth tide effect in triggering earthquakes, and they further reported that the direction of the compressional stress at a region created by the earth tide almost coincides with that of the dominant principal pressure axes of the focal mechanisms at the region. This suggests that there might be specific positions of the Moon, Sun and Earth, known as lunar phases that create effective tidal force for earthquakes at each fault. So that, this paper examines the relationship between earthquakes and the lunar phases in some specific regions of Japan, and the significant effect of earth tide in triggering earthquakes is confirmed.

著者

本島 邦行

出版者

Society of Atmospheric Electricity of Japan

雑誌

Journal of Atmospheric Electricity (ISSN:09192050)

巻号頁・発行日

vol.31, no.1, pp.37-49, 2010 (Released:2012-11-12)

参考文献数

14

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This paper was intended to find out any relation between anomalous line-of-sight propagations in the VHF band and occurrences of earthquakes near the VHF propagation path. The broadcasting waves from Tokyo tower were monitored continuously for 1155 days at Kiryu Gunma. Anomalous propagations were distinguished from the received data by using a statistical analysis. After the statistical thoughtful consideration, it was found out that earthquakes associated with anomalous propagations were characterized by (1) magnitude of earthquakes M≧4.5, (2) distance from epicenters L≦75km and (3) depth of hypocenters D≦50km.

著者

酒井 英男 上坂 麻子 黒沢 尚美 高橋 貞夫 三宅 幸博

出版者

Society of Atmospheric Electricity of Japan

雑誌

Journal of Atmospheric Electricity (ISSN:09192050)

巻号頁・発行日

vol.17, no.2, pp.103-111, 1997 (Released:2021-03-12)

著者

Satoshi Ujigawa Hiroyuki Nakata Shin Shimakura

出版者

Society of Atmospheric Electricity of Japan

雑誌

Journal of Atmospheric Electricity (ISSN:09192050)

巻号頁・発行日

vol.29, no.2, pp.115-123, 2009 (Released:2011-04-12)

参考文献数

10

被引用文献数

1 1

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Observation of 48.25-MHz radio waves transmitted from Bangkok, Thailand, was carried out at Tateyama, Japan, during 2001. Since the radio wave propagates through a crest of equatorial anomaly, which disturbs stratified structure of the ionosphere, it is conceivable that the propagation of the radio wave is affected by three-dimensional structure of the ionosphere. Seasonal and diurnal variations of the signal intensity are quite similar to ƒ0F2 above Guangzhou and also Okinawa, which are located on the great circle path between Bangkok and Tateyama. Using ray-tracing calculations with the distribution of the electron density determined by IRI model, it is also confirmed that the radio wave propagates to Tateyama because of one-hop reflection in the ionosphere and that MUF is mainly dependent on ƒ0F2 above the midpoint between Bangkok and Tateyama. Although the value of ƒ0F2 is almost constant, MUF calculated by the ray-tracing treatment decreases around 14 JST in fall and winter. This decrease is also detected in the observational result of the signal intensity of the radio wave received at Tateyama. The ray tracing calculation shows that the decrease of MUF is due to tilt of the distribution of electron density, which is noticeable in developing the equatorial anomaly. Then discussing the propagation characteristics of 48.25-MHz radio waves crossing equatorial anomaly region, it is important to consider not only the parameters of the ionosphere, e.g. ƒ0F2, but also the tilt of the distribution of electron density.

著者

畑 雅恭 内匠 逸 太田 健次 井筒 潤 藤井 隆司 佐藤 時康 矢橋 清二 渡辺 伸夫

出版者

Society of Atmospheric Electricity of Japan

雑誌

Journal of Atmospheric Electricity (ISSN:09192050)

巻号頁・発行日

vol.30, no.1, pp.37-52, 2010 (Released:2012-04-07)

参考文献数

16

被引用文献数

1

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ELF (30-300 Hz) band three-axial magnetic-flux receiver was developed for detecting electromagnetic-wave precursor of earthquakes and volcanic eruption. The receiver attained a high sensitivity of 0.4pT/√Hz (223Hz) and 4.5 pT/√Hz (17Hz) for the ground based observation of the ambient magnetic flux anomaly. The receiver was extended to detect ultra-low-frequency (ULF) variation (0.1 to 10-7Hz) of crust magnetic flux by through MMD (Modulated Magnetic-flux Detection) reception. It detects the modulated components of the ELF band atmospheric signal which are produced by the crust ULF magnetic-flux variation. The receiver noise due to the artificial noise can be smoothed out from the objective ULF magnetic flux signal by introducing long term integration for the period of 107 seconds of the detected signal. The receiver detected the ULF anomaly of magnetic variation and the Schumann Resonance variation appeared before the two earthquakes of the class M7 occurred in Japan in 2005 and 2007 respectively.