著者

一柳 昌義 高橋 浩晃 山口 照寛 東 龍介 山田 卓司 大園 真子 眞城 亮成 笠原 稔 谷岡 勇市郎

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.78, pp.37-51, 2015-03-19

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An earthquake swarm begun at 15 July 2012 in Nakagawa town of northern Hokkaido. The largest earthquake with MJMA4.3 occurred on 16 July 2012. We carried out temporal seismic observation with seven stations from 18 July 2012 to the last October 2012. Hypocenters were calculated using the Double-Difference hypocenter determination procedure with a local one dimensional P-wave velocity structure. Precise hypocenter data indicated that epicenters were distributed in very narrow area of 2 km×2 km with shallow depth from 4 km to 7 km. Earthquakes after middle of August occurred only in southern part of the region and depth had got shallower with time. Hypocenters indicated no clear alignment in consistent with any nodal planes of major earthquakes. An independent hypocenter cluster with shallower than 2 km was observed above the main activity area. A slow slip event (SSE) with Mw 5.4 coincidentally detected by GNSS crustal deformation data during the swarm. This swarm was situated at the southeastern end of the fault of SSE. This fact suggested that seismic swarm might triggered SSE or was induced by SSE.

著者

前田 宜浩 笹谷 努 一柳 昌義 山口 照寛 高橋 浩晃 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.243-253, 2005-03-15

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

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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.

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

著者

高橋 浩晃 大園 真子 宮町 宏樹 谷岡 勇市郎 蓬田 清 吉澤 和範 中尾 茂 一柳 昌義 山口 照寛 ゴルディエフ エフゲニー ブイコフ ビクター ゲラシメンコ ミハイル シェスタコフ ニコライ ワシレンコ ニコライ プリトコフ アレキサンダ レビン ユーリ ワレンチン ミハイロフ コスティレフ ドミトリ チェブロフ ダニラ セロベトニコフ セルゲイ

出版者

北海道大学

雑誌

基盤研究(A)

巻号頁・発行日

2013-04-01

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ロシア極東地域から中国東北部を含むアジア北東地域のテクトニクスの解明を目指し,地震とGNSS観測を実施した.2011年東北地方太平洋沖地震による広域的な余効地殻変動が観測され,ロシア沿海州地方は地震時変動を上回る変位が得られた.ロシア極東地域に展開した広帯域地震観測網のデータから,当該地域の上部マントル地震波速度構造を明らかにし日本海下に低速度異常を確認した.上部マントルの粘弾性構造の推定から,日本列島周辺で繰り返し発生する巨大地震がアジア北東地域に長期的な余効変動を引き起こしてきた事実を明らかにした.また当該地域の特徴的な地震活動を明らかにした.

著者

前田 宜浩 笹谷 努 一柳 昌義 山口 照寛 高橋 浩晃 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

no.68, pp.243-253, 2005-03

被引用文献数

2

著者

一柳 昌義 高橋 浩晃 山口 照寛 岡田 和見 大園 真子 岡崎 紀俊

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.79, pp.1-8, 2016-03-19

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An M5.0 shallow earthquake occurred on 4 June 2015 in the eastern Hokkaido. In order to evaluate aftershock activity, three temporal seismic stations had been operated in the focal region from 4 June 2015 to 22 August 2015. Hypocenters calculated with a local seismic velocity structure indicated clear southwestern-dipping distribution. This alignment on a plane was consistent with one of nodal plane of mainshock focal mechanism. This earthquake and historical records suggested higher seismic activity in this region.

著者

高波 鐵夫 村井 芳夫 町田 祐弥 斉藤 市輔 牧野 由美 勝俣 啓 山口 照寛 西野 実

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.57, no.3, pp.291-303, 2005-02-20 (Released:2010-03-11)

参考文献数

21

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Nine OBSs (Ocean Bottom Seismographs) were deployed just before the 2003 Tokachi-oki earthquake (M8.0) in the source region, off Hokkaido island, Japan for the period from 7 August to 21 September 2003. The observation area was located about 50-100km landward of the southern Kuril trench where the Pacific plate is subducted toward Hokkaido island. The main shock occurred on 26 September 2003, just several days after this 50-days observation by OBS. Until this big earthquake, the seismic activity in this area has been extremely low in contrast with the adjacent trench areas. No big earthquake has occurred since the 1952 Tokachi-oki earthquake (M8.2). From the phase-reading data, 186 micro- and ultra micro-earthquakes were located in the regular seismic active zones. The b-value of 0.82 from the earthquakes with magnitude from -0.6 to 2.9 could support the fore-shocks of the 2003 Tokachi-oki earthquake. Several interesting phenomena were found in this study as follows. (1) Many clusters of events took place simultaneously in the surrounding source region after a short quiescence period of several days. (2) An enormous number of curious burst signals, which oscillated for only a few seconds, continued to appear at almost OBSs. In particular, at two OBSs DHH and DK being the shortest distance to the Kuril trench, over 3500 bursts of events with amplitudes of 10-7m/s were counted during the observation period. On the other side, OBS DD, which was close to the epicenter of main event and far away from the trench, around the beginning of September 2003, the rate of occurrence abruptly rose to over twice of the previous rate, which has kept the low rate until then. The start time of activation was almost the same time of the appearance of many widespread clusters of earthquakes. These results will be applied to a research project of the great earthquakes occurring along the trenches.