36 0 0 0 OA 地震に先行するVHF(FM放送波)散乱波の観測的研究
- 著者
- 森谷 武男 茂木 透 高田 真秀 笠原 稔
- 出版者
- 北海道大学大学院理学研究科地球惑星科学専攻(地球物理学)
- 雑誌
- 北海道大学地球物理学研究報告 (ISSN:04393503)
- 巻号頁・発行日
- vol.68, pp.161-178, 2005-03-15
3 0 0 0 OA 地震に先行するVHF帯散乱波の観測的研究(II)
- 著者
- 森谷 武男 茂木 透 高田 真秀 山本 勲
- 出版者
- 北海道大学大学院理学研究院自然史科学部門(地球物理学) = Department of Natural History Sciences (Geophysics), Graduate School of Science, Hokkaido University
- 雑誌
- 北海道大学地球物理学研究報告 (ISSN:04393503)
- 巻号頁・発行日
- vol.72, pp.269-285, 2009-03-15
A new observation system established in Hokkaido, northern Japan to confirm a suspected relationship between anomalous radio-wave propagation and impending earthquakes has been documenting anomalous VHF-band radiowave propagation beyond the line of sight prior to earthquakes since December, 2002. During such events, radio waves transmitted from an FM radio station were scattered, such that they could be received by an observation station beyond the transmitting station's line of sight. A linear relationship was established between the logarithm of the total duration time of the anomalous transmissions (Te) and the magnitude (M) or maximum seismic intensity (I) of the impending earthquake for M4- to M5-class earthquakes that occurred at depths of about 50 km beneath the Hidaka Mountains in Hokkaido, Japan in June 2004 and March 2008 as reported in the previous paper (Moriya et al., 2005). Similar linear relationships are also valid for earthquakes that occurred at other depths. Te is longer for shallower earthquakes and shorter for deeper ones. Numerous parameters seem to affect Te, including hypocenter depths and epicentral surface conditions (i.e., sea versus land). This relationship is important because it means that pre-seismic, anomalous transmission of VHF-band waves may be useful in predicting the size of an impending earthquake. To avoid misidentification of FM stations that have identical frequencies, three 64 MHz band transmitters were established, each with a unique frequency. Earthquakes that occurred in and around eastern Hokkaido scattered waves from FM-band and 64 MHz-band stations and provided quantitative relationships between Te and M, and between Te and I. Using the interferometer at the TES observation site, the incident azimuth of the scattering waves from the Hiroo station was measured. Prior to two earthquakes that occurred beneath almost the same part of the Tokachi region at depths of 86 km and magnitudes of M 4.9 and 4.0, the interferometer yielded incident azimuths of S18W and S34W. The true azimuths from TES to the hypocenters of the two earthquakes were S35W and S38W, respectively. These two measurements, therefore, suggest that anomalous transmission of VHF waves is caused by scattering at the epicenters of impending earthquakes.
- 著者
- 一柳 昌義 山口 照寛 高田 真秀 東 龍介 黒井 和典 山田 卓司 高橋 浩晃 前田 宜浩
- 出版者
- 北海道大学大学院理学研究院
- 雑誌
- 北海道大学地球物理学研究報告 (ISSN:04393503)
- 巻号頁・発行日
- vol.76, pp.1-13, 2013-03-19
On December 2, 2010, MJMA4.6 shallow felt earthquake occurred beneath southeastern part of Sapporo city. Three temporal seismic stations were installed near epicentral area. Reliable hypocenter data estimated by double difference procedure with local seismic velocity structure indicated clear southeastern-dipping distribution. Fault plane from focal mechanism estimated from P-wave polarization well agreed with this hypocenter distribution. Geometry of hypocenter distribution was also well consistent with an anticline structure and possible buried active fault estimated for earthquake disaster damage assumption by local government. Recalculation of hypocenters of the 1985, 1990, and 2010 felt earthquakes under equal condition implied that epicentral locations of these three events were approximately same. These facts implied possible stress concentration in epicentral region.
1 0 0 0 OA 投下型地震計(ペネトレータ)の南極・みずほ高原での試験観測 -第43次夏隊報告-
- 著者
- 松島 健 山下 幹也 安原 達二 堀口 浩 宮町 宏樹 戸田 茂 高田 真秀 渡邉 篤志 渋谷 和雄 Takeshi Matsushima Mikiya Yamashita Tatsuji Yasuhara Koh Horiguchi Hiroki Miyamachi Shigeru Toda Masamitsu Takada Atsushi Watanabe Kazuo Shibuya
- 雑誌
- 南極資料 = Antarctic Record (ISSN:00857289)
- 巻号頁・発行日
- vol.47, no.3, pp.395-408, 2003-11
南極氷床上のクレバス帯等の,地上からは到達困難な地域での人工地震観測を目的とした投下型地震観測装置(南極ペネトレータ)を開発し,第43次日本南極地域観測隊で実施する東南極みずほ高原における人工地震探査で使用するために,22本のペネトレータを昭和基地に持ち込んだ.しかし,開発の遅れに伴う国内試験の不足から種々の不具合が発生し,今回は本観測での使用をあきらめざるを得なかった.当初の目的は果たすことができなかったが,国内では得られない環境でのペネトレータ投下実験を行い,投下姿勢,着地衝撃力,温度変化等の貴重なデータを得るとともに,南極内陸部での実際のヘリコプター運用への知見を得ることができた.これらの成果はペネトレータ型地震計の改良のみならず,今後の各種投下型観測機器の開発・製作に多いに役に立つものと考えられる.
- 著者
- 一柳 昌義 山口 照寛 高田 真秀 東 龍介 黒井 和典 山田 卓司 高橋 浩晃 前田 宜浩
- 出版者
- 北海道大学大学院理学研究院
- 雑誌
- 北海道大学地球物理学研究報告 (ISSN:04393503)
- 巻号頁・発行日
- no.76, pp.1-13, 2013-03
1 0 0 0 OA 2016年6月16日に発生した函館市南茅部付近の地震(MJMA 5.3)と余震活動
- 著者
- 一柳 昌義 高田 真秀 高橋 浩晃
- 出版者
- 北海道大学大学院理学研究院
- 雑誌
- 北海道大学地球物理学研究報告 (ISSN:04393503)
- 巻号頁・発行日
- vol.80, pp.1-11, 2017-03-19
A M5.3 shallow earthquake occurred on 16 June 2016 in Minamikayabe region, southern Hokkaido. Three temporal seismic stations had been operated in the focal region from 18 June 2016 to 29 August 2016. Initial hypocenters and 1-D P-wave velocity structure were estimated from waveform data of temporal and permanent seismic stations. Fine aftershock distribution inferred from the double-difference procedure showed that the hypocenters were distributed in NW-SE direction, which might be agree with a fault plane of mainshock focal mechanism. Five foreshocks occurred near mainshock hypocenter showed similar waveform with high correlation. Characteristic persistent background seismicity and latest middle size earthquake might be related to high geothermal gradient in this region.