著者

石原 吉明 束田 進也 酒井 慎一 平松 良浩 古本 宗充

出版者

東京大学地震研究所

雑誌

東京大学地震研究所彙報 (ISSN:00408972)

巻号頁・発行日

vol.76, no.1, pp.87-92, 2001-07-25

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Fireballs, which are caused by high-velocity passages of meteorites through the atmosphere, generate shock waves. It has been known that such shock waves are often recorded on seismograms. It is possible to determine the trajectories and the sizes of a fireball using seismological records. We have searched shock wave signals from many bright fireballs observed in the period from September 1996 to November 1998, and the 1999 Kobe meteorite. The shock waves from one large fireball, which is called the Miyako fireball, and the Kobe meteorite are clearly recorded on many seismograms. In particular, the shock waves from the former fireball are widely recorded by the dense seismic array of 1997-98 joint seismic observations in the Tohoku Backbone Range. We determine their trajectories. Amplitudes of the shock waves are found to be possibly correlated with the masses of the meteorites. It is also indicated that the shock waves from fireballs, which are darker than brightness magnitude -10, are too weak to be recognized on the seismograms of ordinary seismic stations in Japan.

著者

笠松 健太郎 山中 浩明 酒井 慎一

出版者

社団法人 物理探査学会

雑誌

物理探査 (ISSN:09127984)

巻号頁・発行日

vol.68, no.4, pp.265-275, 2015

被引用文献数

1

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&nbsp;&nbsp;地震動評価で重要となるS波速度構造モデルの構築に資するため,深部地盤の二次元S波速度構造を推定する手法について検討した。本手法では,二次元仮定が成立する伝播経路を対象とした構造推定のため,はじめに観測記録を分析してラブ波伝播特性を調べる。次に,ラブ波がほぼ同じ方向に伝播する測線上の観測記録を用いて,ラブ波を対象とした波形インバージョンを行い,二次元S波速度構造を推定する。提案手法を2011年富士山付近の地震(<i>M</i>_J6.4)を対象とした地震動の三次元シミュレーションによる周期6~10秒の速度波形に適用し,手法の妥当性を確認した。この手法を同地震の相模原と世田谷を結ぶ測線上の地震観測記録に適用し,この断面の二次元速度構造を推定した。観測記録のラブ波成分は良く再現され,推定結果の速度構造は地震調査研究推進本部(2009)のモデルに比べて堆積層が薄く求められた。この結果の妥当性を確認するため,観測記録のcoda部分を用いて水平上下スペクトル比を算定し,理論によるレイリー波の基本モードの楕円率と比べた。観測されたピーク周期は推定結果の方と良く一致しており,構造モデルが妥当であると考えられることを確認した。<br>

著者

清水 洋 松本 聡 酒井 慎一 岡田 知己 渡辺 俊樹 飯尾 能久 相澤 広記 松島 健 高橋 浩晃 中尾 茂 鈴木 康弘 後藤 秀昭 大倉 敬宏 山本 希 中道 治久 山中 浩明 神野 達夫 三宅 弘恵 纐纈 一起 浅野 公之 松島 信一 福岡 浩 若井 明彦 大井 昌弘 田村 圭子 木村 玲欧 井ノ口 宗成 前原 喜彦 赤星 朋比古 宇津木 充 上嶋 誠 王 功輝 ハザリカ ヘマンタ 矢田 俊文 高橋 和雄

出版者

九州大学

雑誌

特別研究促進費

巻号頁・発行日

2016-04-22

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2016年熊本地震について、地震活動や地殻変動、活断層、火山活動への影響、地震災害の特徴などを調査した。その結果、熊本地震は布田川・日奈久断層帯の右横ずれ運動によって発生したが、複数の断層面と複雑な断層形状を持つことを明らかにした。また、建物被害や土砂災害の地盤との関係、特に、地盤の過剰間隙水圧が地すべりの発生要因であることを明らかにした。さらに、災害情報や災害過程、被災救援、エコノミークラス症候群などについての調査から、広域複合災害の問題点と対応策を提示した。

著者

津野 靖士 明田川 保 山中 浩明 翠川 三郎 山本 俊六 三浦 弘之 酒井 慎一 平田 直 笠原 敬司 木村 尚紀

出版者

公益社団法人 日本地震工学会

雑誌

日本地震工学会論文集

巻号頁・発行日

vol.12, no.5, pp.5_102-5_116, 2012

被引用文献数

7

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2011年東北地方太平洋沖地震の本震と余震の強震記録を用いて、首都圏および周辺地域に於ける周期2秒以上の地震動特性とサイト増幅特性を評価した。約650点の本震記録を用いたPGVとPGAから地震動が首都圏で複雑な分布を示すこと、擬似速度応答スペクトル分布から川崎~品川付近の東京湾沿岸部で周期2秒と3秒の速度応答が極めて大きいことが分かった。地表/地中の速度応答スペクトル比から算出したサイト増幅特性は、周期3秒以上の地震動に対して震源の位置に依存し、首都圏およびその周辺地域では東北地方の地震よりも長野県北部や静岡県東部の地震による地震動が大きく増幅されることが分かった。

著者

川北 優子 酒井 慎一

出版者

東京大学

雑誌

東京大學地震研究所彙報 (ISSN:00408972)

巻号頁・発行日

vol.84, no.2, pp.127-139, 2010-01-28

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The Special Project for Earthquake Disaster Mitigation in the Tokyo Metropolitan Area has been ongoing (2007−2012). Under this project, the Metropolitan Seismic Observation network (MeSO-net), which consists of about 400 observation sites, has been constructed. The correlations of waveform from local and teleseismic events are high because observation sites are deployed at about 2 or 3-km intervals. In addition, the later phase is easily identified although artificial noise is very intense. However, we are attempting to improve quality by characterizing the various types of noise. In the metropolitan area, various human activities are observed that generate noise such as trains, automobiles, aircrafts, factories, and electrical power. These adversely affect our observations. We recognize various types of noise from continuous records. A spectral graph and a spectrogram in each station are useful for characterizing signals and noise. We also discovered a form of system noise obtained from the relationship between sensor and electrical circuit. We named it Aurora Noise. The strength of Aurora Noise was reduced by improving the electrical circuit. Our study will lead to improving the quality of observed data, and contribute to a new assessment of seismic hazard in the Tokyo Metropolitan Area in Japan.

著者

笠原 敬司 酒井 慎一 森田 裕一 平田 直 鶴岡 弘 中川 茂樹 楠城 一嘉 小原 一成

出版者

東京大学

雑誌

東京大學地震研究所彙報 (ISSN:00408972)

巻号頁・発行日

vol.84, no.2, pp.71-88, 2010-01-28

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To better assess the seismic hazards produced by a magnitude 7 or greater (M 7+) earthquake in the Tokyo metropolitan area, we have launched the Special Project for Earthquake Disaster Mitigation in Tokyo Metropolitan area (2007−2011). This requires establishing a highly dense seismic-array observation network in and around Tokyo to monitor ongoing micro-earthquakes with relatively high precision even if noise levels are generally high. We have started developing the Metropolitan Seismic Observation network (MeSO-net). Deployment of MeSO-net seismic stations is currently underway. The number of observatories at project termination will be 400 with a 2−5km interval in space. In this paper, we summarize how we solved technically difficult and practical problems involved in MeSO-net construction. We start with a review of related work to better understand the technical difficulties involved in deploying stations in metropolitan areas such as Tokyo. Next, we explain our approach to verifying a meaningful design of an observatory and its deployment at local sites. We further describe our decision-making process in practice for implementing station deployment. We hope that establishing the MeSO-net will support a new assessment of the seismic hazards produced by M 7+ earthquakes in the Tokyo metropolitan area.

著者

中村 亮一 鶴岡 弘 加藤 愛太郎 酒井 慎一 平田 直

出版者

公益社団法人 日本地震工学会

雑誌

日本地震工学会論文集 (ISSN:18846246)

巻号頁・発行日

vol.20, no.1, pp.1_1-1_12, 2020 (Released:2020-01-31)

参考文献数

15

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関東地方には約300点の加速度計から構成される高密度なMeSO-netが展開されており,2008年から連続波形記録が蓄積されている.これら高密度観測記録を用いることで,より高分解能の三次元減衰構造を求めることができることが期待される.ただし,各地震計は地中約20mの深さに設置されており,観測波形記録には地表からの反射波の影響が含まれると考えられるため,これらの影響を考慮してゆく必要がある.そこで,まず波形記録のスペクトルに現れる特徴を調べた.その結果,地中設置のためスペクトルに谷が形成されていることが確認できた.次に,MeSO-netとK-NET及びKiK-net記録を用いた三次元Q値とサイト増幅特性の同時インバージョンを行い,地中設置による地盤増幅特性への影響について解析を実施した.ここで,地盤増幅は卓越周期からグループ化し,それぞれのグループで同じ増幅をもつと仮定する手法であり,K-NET及びKiK-netの地表観測地点は8グループに分け,MeSO-netの地中記録は,それとは別の2グループに分けた.その結果,減衰構造は先行研究と整合した結果が得られた.地中設置の場合でも,その増幅率を適切に考慮することにより減衰構造を求めることができることを確認した.また,平均的にみて地中記録の増幅特性は地表の岩盤サイトに類似しており,地表の地盤の差異による影響に比べて小さいことがわかった.

著者

中川 茂樹 鶴岡 弘 川北 優子 酒井 慎一 平田 直

出版者

東京大学地震研究所

雑誌

地震研究所彙報 (ISSN:00408972)

巻号頁・発行日

vol.84, no.2, pp.107-114, 2009

---

We launched the Special Project for Earthquake Disaster Mitigation in the Metropolitan Tokyo area to obtain high-resolution images of three-dimensional seismic wave velocity and attenuation structures. The core item of this project is a dense seismic array called MeSO-net for making observations in the metropolitan area. MeSO-net consists of 400 seismic stations, from which data are continuously collected at the Data Center at ERI. At the Sub-Center at NIED, data are backed up and integrated with Hi-net data. Seismic data with a sampling rate of 200 Hz are transmitted to the Data Center using ACT protocol. Data from all stations are received at the Data Center at ERI. After checking the quality (including lost packets) of data received, data are automatically processed and archived using the WIN system. This observational network and the Data Center are equipped with several new functions for reliable data transmission and ease of maintenance.

著者

川北 優子 酒井 慎一

出版者

東京大学地震研究所

雑誌

地震研究所彙報 (ISSN:00408972)

巻号頁・発行日

vol.84, no.2, pp.127-139, 2009

---

The Special Project for Earthquake Disaster Mitigation in the Tokyo Metropolitan Area has been ongoing (2007−2012). Under this project, the Metropolitan Seismic Observation network (MeSO-net), which consists of about 400 observation sites, has been constructed. The correlations of waveform from local and teleseismic events are high because observation sites are deployed at about 2 or 3-km intervals. In addition, the later phase is easily identified although artificial noise is very intense. However, we are attempting to improve quality by characterizing the various types of noise. In the metropolitan area, various human activities are observed that generate noise such as trains, automobiles, aircrafts, factories, and electrical power. These adversely affect our observations. We recognize various types of noise from continuous records. A spectral graph and a spectrogram in each station are useful for characterizing signals and noise. We also discovered a form of system noise obtained from the relationship between sensor and electrical circuit. We named it Aurora Noise. The strength of Aurora Noise was reduced by improving the electrical circuit. Our study will lead to improving the quality of observed data, and contribute to a new assessment of seismic hazard in the Tokyo Metropolitan Area in Japan.

著者

森田 裕一 酒井 慎一 中川 茂樹 笠原 敬司 平田 直 鏡 弘道 加藤 拓弥 佐藤 峰司

出版者

東京大学地震研究所

雑誌

地震研究所彙報 (ISSN:00408972)

巻号頁・発行日

vol.84, no.2, pp.89-105, 2009

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The Autonomous Cooperative data Transfer Protocol (ACT protocol) is one of the data transfer protocols based on UDP/IP developed for the Metropolitan Seismic Observation network (MeSO-net). It has a robust re-send function to prevent data from being lost in the Internet route. Moreover, it also has a function to adjust the data transmission rate considering the quality of the Internet route and the load on the data-receiving system. If the Internet route is too busy to send all data, the transmission rate from the observation station is decreased automatically to ease the Internet traffic jam, and data that cannot be sent because of the limitation on the transmission rate are stored at each station. After conditions recover, the stored data are sent automatically at an increasing transmission rate and gradually catch up with real-time data. The transmission rate is decided by data transmission equipment at the station using pre-loaded algorithms, not at the data center. Therefore, the load at data center equipment is not so high even if the equipment receives data from hundreds of stations. We describe an overview of the ACT protocol, flow charts, and data format used in the protocol. We also demonstrate that the ACT protocol is very powerful for the vast size of the seismograph network composed of several hundred stations. The ACT protocol is generally applicable and can be used for data transmission systems in other scientific fields.

著者

吉田 治雄 小林 喜久二 佐藤 吉之 梅田 尚子 酒井 慎一 平田 直

出版者

人工知能学会

雑誌

人工知能学会全国大会論文集 (ISSN:13479881)

巻号頁・発行日

vol.31, 2017

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GAを用いた地震観測記録の逆解析により関東平野内の地下構造の推定を実施した。使用した観測点はK-NET、KiK-net(防災科研)、MeSO-net(東大地震研)である。各点の推定地盤モデルに基づいて3次元堆積平野モデルを構築し3次元差分法により地震動のシミュレーションを実施した。既往の地盤モデルによるシミュレーション結果との比較により本研究の計算波は観測記録との適合性がより良いことが確認された。

著者

森田 裕一 酒井 慎一 中川 茂樹 笠原 敬司 平田 直 鏡 弘道 加藤 拓弥 佐藤 峰司

出版者

東京大学地震研究所

雑誌

地震研究所彙報 (ISSN:00408992)

巻号頁・発行日

vol.84, no.2, pp.89-105, 2009

---

The Autonomous Cooperative data Transfer Protocol (ACT protocol) is one of the data transfer protocols based on UDP/IP developed for the Metropolitan Seismic Observation network (MeSO-net). It has a robust re-send function to prevent data from being lost in the Internet route. Moreover, it also has a function to adjust the data transmission rate considering the quality of the Internet route and the load on the data-receiving system. If the Internet route is too busy to send all data, the transmission rate from the observation station is decreased automatically to ease the Internet traffic jam, and data that cannot be sent because of the limitation on the transmission rate are stored at each station. After conditions recover, the stored data are sent automatically at an increasing transmission rate and gradually catch up with real-time data. The transmission rate is decided by data transmission equipment at the station using pre-loaded algorithms, not at the data center. Therefore, the load at data center equipment is not so high even if the equipment receives data from hundreds of stations. We describe an overview of the ACT protocol, flow charts, and data format used in the protocol. We also demonstrate that the ACT protocol is very powerful for the vast size of the seismograph network composed of several hundred stations. The ACT protocol is generally applicable and can be used for data transmission systems in other scientific fields.

著者

川北 優子 酒井 慎一

出版者

東京大学地震研究所

雑誌

地震研究所彙報 (ISSN:00408992)

巻号頁・発行日

vol.84, no.2, pp.127-139, 2009

---

The Special Project for Earthquake Disaster Mitigation in the Tokyo Metropolitan Area has been ongoing (2007−2012). Under this project, the Metropolitan Seismic Observation network (MeSO-net), which consists of about 400 observation sites, has been constructed. The correlations of waveform from local and teleseismic events are high because observation sites are deployed at about 2 or 3-km intervals. In addition, the later phase is easily identified although artificial noise is very intense. However, we are attempting to improve quality by characterizing the various types of noise. In the metropolitan area, various human activities are observed that generate noise such as trains, automobiles, aircrafts, factories, and electrical power. These adversely affect our observations. We recognize various types of noise from continuous records. A spectral graph and a spectrogram in each station are useful for characterizing signals and noise. We also discovered a form of system noise obtained from the relationship between sensor and electrical circuit. We named it Aurora Noise. The strength of Aurora Noise was reduced by improving the electrical circuit. Our study will lead to improving the quality of observed data, and contribute to a new assessment of seismic hazard in the Tokyo Metropolitan Area in Japan.

著者

中川 茂樹 鶴岡 弘 川北 優子 酒井 慎一 平田 直

出版者

東京大学地震研究所

雑誌

地震研究所彙報 (ISSN:00408992)

巻号頁・発行日

vol.84, no.2, pp.107-114, 2009

---

We launched the Special Project for Earthquake Disaster Mitigation in the Metropolitan Tokyo area to obtain high-resolution images of three-dimensional seismic wave velocity and attenuation structures. The core item of this project is a dense seismic array called MeSO-net for making observations in the metropolitan area. MeSO-net consists of 400 seismic stations, from which data are continuously collected at the Data Center at ERI. At the Sub-Center at NIED, data are backed up and integrated with Hi-net data. Seismic data with a sampling rate of 200 Hz are transmitted to the Data Center using ACT protocol. Data from all stations are received at the Data Center at ERI. After checking the quality (including lost packets) of data received, data are automatically processed and archived using the WIN system. This observational network and the Data Center are equipped with several new functions for reliable data transmission and ease of maintenance.

著者

三上 岳彦 森島 済 日下 博幸 高橋 日出男 赤坂 郁美 平野 淳平 佐藤 英人 酒井 慎一 大和 広明

出版者

帝京大学

雑誌

基盤研究(A)

巻号頁・発行日

2013-10-21

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東京首都圏に設置した独自の気温・湿度観測網と気圧観測網のデータ等を用いて、夏季日中のヒートアイランドの時空間変動を明らかにするとともに、熱的低気圧の動態と局地的短時間強雨発生との関連およびその要因の解明を試みた。夏季の気温と気圧データに主成分分析を適用した結果、上位主成分に、海陸風循環、ヒートアイランド、北東気流に関連した空間分布が認められた。局地的短時間強雨の事例解析を行い、豪雨発生の前後で気圧の低下と上昇が起こり、海風起源の水蒸気量の増加が確認できた。領域気象モデル(WRF)による都市域での短時間強雨発生に関する数値実験を行い、都市域で夜間の降水が増えていることが明らかになった。

著者

酒井 慎一 山田 知朗 井出 哲 望月 将志 塩原 肇 卜部 卓 平田 直 篠原 雅尚 金沢 敏彦 西澤 あずさ 藤江 剛 三ヶ田 均

出版者

公益社団法人 東京地学協会

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.110, no.2, pp.145-155, 2001-04-25 (Released:2009-11-12)

参考文献数

6

被引用文献数

38 54

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From June 26, 2000, an intensive earthquake swarm started under Miyake-jima Island, 180 km south off Japan. This swarm was closely related to the eruption of Miyake-jima Island, probably dominated by underground magmatic activity. The swarm spread toward the northwestern ocean region from Miyake-jima Island, in which a huge number of earthquakes (over 100, 000) including five large events of M>6.0 were detected over about two months. This earthquake swarm was the most active since we started seismic observations in the 1970's.Although there are some telemetered observation stations on the Izu volcanic islands, no offshore instruments were operated in the area of this earthquake swarm. To understand both the spatial and temporal changes of this activity, we conducted a series of ocean bottom seismometer observations. According to the variation in the seismic activity with time, we changed the array configuration of OBSs six times. Furthermore, real-time seismic observations were undertaken using a buoy-telemetering OBS system.Combining the OBS data with those of the island stations, very precise earthquake locations were determined. The epicenter distribution obtained strongly indicates a northwest-southeastern lineament. The vertical cross-section of the events shows two characteristic trends. Deeper (7- 13km) events are forming a very thin (2-km thick) plane, while shallower ones (< 7 km) show a much thicker distribution. These distribution patterns will provide important constraints on the physical mechanism for understaning magma migration.