著者

萩原 幸男 長沢 工 大久保 修平

出版者

東京大学地震研究所

雑誌

東京大學地震研究所彙報 = Bulletin of the Earthquake Research Institute, University of Tokyo (ISSN:00408972)

巻号頁・発行日

vol.61, no.3, pp.529-535, 1987-02-10

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1847年善光寺地震のとき発生した断層は垂直変位をもつので,断層をはさむ両側のブーゲー異常に差が生じている可能性がある.断層によるブーゲー異常の乱れの発見を目的として,長野市街地を中心に84点の重力測定を実施した.しかし結果として,期待されたコンターの乱れは発見されなかった.この地震断層の西側に隣接して,顕著な低ブーゲー異常帯が存在することが判明した.これは断層破砕帯のような待異な構造に関連するものかもしれない.

著者

宇津 徳治

出版者

東京大学地震研究所

雑誌

東京大學地震研究所彙報 = Bulletin of the Earthquake Research Institute, University of Tokyo (ISSN:00408972)

巻号頁・発行日

vol.63, no.1, pp.23-31, 1988-06-30

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日本の地震について,震央付近の震度I0(気象庁震度階級),マグニチュードM(気象庁方式),震源の深さh(km)の標準的関係を表す実験式を1114個の震度データを用いて求め,次式を得た.M=0.23 I0+0.105 I02+1.2log h+1.3この式はMが2~8,hがO~100km.I0がO~6の地震を対象としている.ただしh=Oと発表されている地震の実際の深さは数kmと考えて,h<3kmの場合はh=3kmと置く,Mが5程度より大きい地震についてはm=1.2I0+1.21log h-0.83すなわちI0=O.83 M-log h+0.71を用いてもよい.

著者

宇津 徳治

出版者

東京大学地震研究所

雑誌

東京大學地震研究所彙報 = Bulletin of the Earthquake Research Institute, University of Tokyo (ISSN:00408972)

巻号頁・発行日

vol.57, no.3, pp.401-463, 1983-01-17

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A catalog of earthquakes of magnitude 6 or more felt in Japan and smaller earthquakes which caused damage in Japan from 1885 through 1980 is presented. The catalog also contains unfelt earthquakes of M≧6 which occurred in the vicinity of Japan (region A indicated in the map), but the listing of unfelt earthquakes may be incomplete for the years before 1924. The catalog is incomplete for deep earthquakes before 1900. The main sources of materials are Utsu's catalog of 1979 (revised in 1982) for 1885-1925, the new JMA catalog (1982) for 1926-1960, and the JMA Seismological Bulletin for 1961-1980. Gutenberg-Richter's catalog (1954), ISS, or ISC Bulletins are used for focal coordinates of earthquakes occurring outside of the network of JMA stations. For some earthquakes the author has determined the focal coordinates or magnitudes. Statistical analyses of the catalog and studies of seismicity patterns in relation to the occurrence of great earthquakes will be published elsewhere.

著者

宇津 徳治

出版者

東京大学地震研究所

雑誌

東京大學地震研究所彙報 = Bulletin of the Earthquake Research Institute, University of Tokyo (ISSN:00408972)

巻号頁・発行日

vol.59, no.2, pp.219-233, 1984-10-20

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日本の浅発地震(ただし東日本の太平洋岸沖合を除く)に対する震度I(気象庁震度階級),震央距離Δ(km),マグニチュードM(気象庁方式)の標準的関係を表わす実験式を181個の地震(M:5~8)の震度データを用いて求めた.このような標準式を定めるうえで生ずるいくつかの問題について議論したが,若干の問題は解決が困難で適当に処理せざるを得ない.本論文ではI-Δの平均回帰直線I=I100-b(Δ-100)の定数を,次の式でMと結んだものを標準式として提出する.I100=1.5M-6.5 b=0.0767-0.015M+0.0008M2なお,使用目的によっては本文中に掲げられている別の式を用いるほうが適当な場合もあろう.

著者

宇津 徳治

出版者

東京大学地震研究所

雑誌

東京大學地震研究所彙報 = Bulletin of the Earthquake Research Institute, University of Tokyo (ISSN:00408972)

巻号頁・発行日

vol.57, no.1, pp.111-117, 1982-07-16

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On the basis of newly collected data, a revision of the catalog of earthquakes in Japan between 1885 and 1925 (UTSU, 1979) has been made.

著者

Utsu Tokuji

出版者

東京大学地震研究所

雑誌

東京大學地震研究所彙報 = Bulletin of the Earthquake Research Institute, University of Tokyo (ISSN:00408972)

巻号頁・発行日

vol.59, no.1, pp.53-66, 1984-07-10

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Four renewal models have been applied to several seismic regions of Japan where large earthquakes occur repeatedly at fairly regular time intervals. The model parameters have been determined by the method of moments and the method of maximum likelihood. The four models represent the distributions of time intervals fairly well, though different models are best suited for different sets of data. The probability of the occurrence of the next large earthquake during a specified interval of time can be calculated easily for each model. Some sample results are presented.

著者

Abe Katsuyuki Kanamori Hiroo

出版者

東京大学地震研究所

雑誌

東京大學地震研究所彙報 = Bulletin of the Earthquake Research Institute, University of Tokyo (ISSN:00408972)

巻号頁・発行日

vol.48, no.6, pp.1011-1021, 1971-01-30

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Group velocities of long-period Rayleigh and Love waves are measured, by band-pass filtering and group-delay time methods, to study regional differences in a deep island arc structure. The measurements are made, over a period range 20 to 80 sec, for propagation paths across the Japan Sea. At longer periods, the observed group velocities of Rayleigh and Love waves are lower by as much as 0.1 km/sec than those for normal oceanic paths. It is found that the ARC-1 model, which was previously introduced to explain the low group velocities of long-period surface waves travelling across the Philippine Sea, can also explain these low group velocities. The major feature of this model is a reduction of mantle shear-velocity by 0.3 to 0.4 km/sec, or 8%, over a depth range 30 to 60 km as compared with that for normal oceanic models. This low mantle velocity and the high heat flow which was previously reported for this region suggest common causes such as high temperature and partial melting. The velocity contrast found here can be explained in terms of a 500℃ temperature excess coupled with a 4% partial melting.|長周期表面波の群速度をもちいて,弧状列島の縁海である日本海のマントル構造を調べた.日本北部及び千島列島の5つの地震についてソウルにおける長周期地震計の記録から,バンド・パス・フィルターとグループ・ディレイ・タイム法を利用して周期20秒から80秒までの群速度を求めた.日本海を横切る表面波の群速度は標準的な海のものにくらべ長周期のところでレイレー波ラブ波ともに0.1km/secほど遅い.この遅い群速度は以前にフィリッピン海を横切る表面波の遅い群速度を説明するためにもちいたARC-1モデルで同じように良く説明される.このモデルの重要な特徴は標準的な海のモデルにくらべてマントルの横波の速度が深さ30~60kmにわたって0.3~0.4km/secまたは8%ほど遅くなっていることである.この浅い所における低速度層の存在と日本海での高熱流量とを考えあわせると.日本海の下のマントル内では他の地域にくらべて温度が高く,またそれによって部分溶融が生じていると考えられる.この考えにしたがうと8%の横波の速度差は4%程度の部分溶融をともなった500℃の温度差で説明される.

著者

佃 為成 酒井 要 橋本 信一 羽田 敏夫 小林 勝

出版者

東京大学地震研究所

雑誌

東京大學地震研究所彙報 = Bulletin of the Earthquake Research Institute, University of Tokyo (ISSN:00408972)

巻号頁・発行日

vol.63, no.3, pp.237-272, 1988-12-23

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北部フォッサマグナの中央隆起帯を横断する千曲川構造線の東端に位置する長野県小県郡丸子町付近で1986年8月24日,M4.9の地震が発生した.ここは2つの火山前線がぶつかる点のすぐ背後でもある.通常の地震活動レベルは低いが,過去には1912年の上田市付近の地震(M5.2)がある.丸子町の地震活動は前震・本震・余震系列と本震の10日後から始まった群発地震が重なったものであった.2回の主要な活動ピークをもつ例は,北部フォッサマグナ地域では少なくなく,ピーク間の間隔は1918年大町地震の13時間,1969年焼岳の地震の2日,1912年上田の地震の5日,今回の地震の12日,1963年燕岳の地震の20日,1897年上高井の地震の104日というように様々である.2回目が群発地震であったのは丸子の地震と,燕岳の地震,上田の地震である.現地における臨時観測によって精密な震源分布が得られた.震源域は時間とともに拡大したが群発地震後最終的には東西3km,南北2km,深さは6kmを中心に3kmの幅をもつ拡がりであった.定常観測網で求めた震源との比較を行い,観測網に依存する震源の系統的なずれやその値のバラツキから震源の絶対精度と相対精度を推定した.MO~4.5の間のM別頻度分布はGutenberg-Richterの関係から少しずれる.群発地震の回数の減衰(p~2)は本震直後の余震のそれ(p~1)と比べ大きい.燕岳の地震ではどちらもp~2であった.本震の震源断層は発震機構及び余震分布の特性から西上り東落ちの高角逆断層である.これは中央隆起帯東縁でのテクトニックな変動と調和する.1986年の千曲構造線の地震活動はそのピークが東南東から西北西へ約150km/yearの速度で伝播した.1912年~1918年にもこの構造線の両端付近で地震があった.約70年の間隔を置いて同じような活動を繰り返したことになる.

著者

Mogi Kiyoo

出版者

東京大学地震研究所

雑誌

東京大學地震研究所彙報 = Bulletin of the Earthquake Research Institute, University of Tokyo (ISSN:00408972)

巻号頁・発行日

vol.41, no.3, pp.615-658, 1963-09-30

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In the preceding papers40', the patterns of the successive occurrence of elastic shocks accompanying fractures under a simple stress state have been experimentally investigated and they have been classified into three types. The type of shock sequence is decidedly influenced by the mechanical structure of model materials. In this paper, this experimental conclusion has been applied to earthquakes in and near Japan (1926-1961). The main results are summarized as follows. (1) The patterns of earthquake sequences are also classified into the three types which were obtained in the patterns of shock sequences, but the transition from one to another is continuous. (2) About 60 earthquakes preceded by foreshocks (the second type)'have been found. They distribute in groups at certain regions. In such regions where the normal sequence of foreshocks is expected, the seismic- observations may give a clue for prediction of major earthquakes. (3) The regions where a certain type of earthquake sequence frequently appears distribute following a general tendency. The various patterns of earthquake sequences are related to the various degrees of heterogeneity in structure. Thus, the spatial distribution of the regions fractured in various degrees are deduced from the data of the patterns of earthquake sequences. (4) The probability P that an earthquake is followed by aftershocks increases with the magnitude and decreases with the focal depth. Furthermore, the P value varies remarkably in various regions. The spatial distribution of the regions having a high P value of aftershock occurrence is nearly identical to that of the second type and the third type. These regions are also the regions which are fractured to some degree. (5) The spatial distribution of fractured regions deduced from the types of the pattern of earthquake sequences has close relations to various geotectonic structures of the Japanese islands, and to other geophysical data.

著者

村井 勇 松田 時彦

出版者

東京大学地震研究所

雑誌

東京大學地震研究所彙報 = Bulletin of the Earthquake Research Institute, University of Tokyo (ISSN:00408972)

巻号頁・発行日

vol.50, no.3, pp.303-327, 1976-03-31

著者

萩原 幸男 村田 一郎 田島 広一 長沢 工 井筒屋 貞勝 大久保 修平

出版者

東京大学地震研究所

雑誌

東京大學地震研究所彙報 = Bulletin of the Earthquake Research Institute, University of Tokyo (ISSN:00408972)

巻号頁・発行日

vol.61, no.4, pp.563-586, 1987-03-31

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埼玉県北西部の関東山地北東縁部には,深谷断層,櫛挽断層,江南断層,今市-菅谷断層等の活断層が密集している.この地帯に7回にわたって合計約630点の重力測定を実施した.得られたブーゲー異常から,地質地形調査ではかつて指摘されたことのない断層を児玉町に発見した.また櫛挽断層は従来考えられていた規模より遙かに大きく,北西にはこの児玉町の断層に,南東には荒川を越えて今市-菅谷断層に連続していることが判明した.1931年西埼玉地震(M7.0)の震源断層は恐らくこの一連の断層と関連があるものと思われる.

著者

羽鳥 徳太郎

出版者

東京大学地震研究所

雑誌

東京大學地震研究所彙報 = Bulletin of the Earthquake Research Institute, University of Tokyo (ISSN:00408972)

巻号頁・発行日

vol.57, no.3, pp.525-535, 1983-01-17

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A small tsunami was generated by the Urakawa-oki earthquake (M=7.1) near Cape Erimo, southern Hokkaido, on March 21, 1982. At Urakawa, the initial disturbance of the present tsunami began with an upward motion simultaneous with the earthquake occurrence. The first wave period was 16min and the third wave was the highest with a semi-amplitude of 80 cm. According to the author's method based on the attenuation of wave-amplitude with distance, the tsunami magnitude (Imamura-Iida scale) are estimated to be m = 0. This rank is average for an earthquake having a magnitude of M=7.1. The source area of the present tsunami which inferred from an inverse refraction diagram is located along the coast from Urakawa to Shizunai. The length of the tsunami source is 40 km and the width 20 km. The tsunami source area agrees with the aftershock area. From the analysis of the initial tsunami motion on the records, an average uplift of 14 cm may have occurred at the sea-bottom of the source area.

著者

伯野 元彦 大谷 圭一

出版者

東京大学地震研究所

雑誌

東京大學地震研究所彙報 = Bulletin of the Earthquake Research Institute, University of Tokyo (ISSN:00408972)

巻号頁・発行日

vol.57, no.3, pp.581-608, 1983-01-17

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The Urakawa-Oki earthquake of M=7.1 occurred on March 21, 1982 and consequently cause some damage to small towns in the south part of Hokkaido. This report describes the earthquake-induced damage to the various types of structures and life lines: Houses and buildings, Roads, Railways. Water supply systems, Electric power and communication systems, Landslides and land failures. The following characteristic features of the damage due to the earthquake are recognized, 1. Wooden houses on soft peat ground suffered damage owing to the destruction of the peat ground itself. On the other hand, reinforced concrete buildings on soft peat ground always have a deep pile foundation and suffered almost no damage. Authors suppose the peat layer to be so soft that it acts like a high cut filter and high frequency components of the incident ground motion which are the main components of high acceleration, is reduced. 2. Most lifeline systems such as water, electric supply systems, and traffic, lost their functions due to the earthquake, and people were subjected to inconveniences. For example, it took 30 days to rehabilitate the railway traffic in this area.

著者

宇佐美 龍夫

出版者

東京大学地震研究所

雑誌

東京大學地震研究所彙報 = Bulletin of the Earthquake Research Institute, University of Tokyo (ISSN:00408972)

巻号頁・発行日

vol.51, no.3-4, pp.209-230, 1977-05-25

著者

岸上 冬彦

出版者

東京大学地震研究所

雑誌

東京大學地震研究所彙報 = Bulletin of the Earthquake Research Institute, University of Tokyo (ISSN:00408972)

巻号頁・発行日

vol.36, no.2, pp.227-233, 1958-07-23

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The Shonai earthquake took place on Oct. 22, 1894, about 400 km north from Tokyo in Yamagata Prefecture. Sometimes it is called the Sakata earthquake because the earthquake damage was great at Sakata City. The reports of their earthquake were few in number, several unknown data were shown the writer by Mr. S. Sato of the Sakata Library. Then the new data were looked over for this paper.

著者

寺田 暁彦 中川 光弘 大島 弘光 青山 裕 神山 裕幸

出版者

東京大学地震研究所

雑誌

東京大學地震研究所彙報 = Bulletin of the Earthquake Research Institute, University of Tokyo (ISSN:00408972)

巻号頁・発行日

vol.79, no.1-2, pp.17-26, 2004

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In this paper, the authors describe remarkable thermo-activities especially at the fumaroles B on the southwestern cliff of the summit dome on Tarumae volcano, which unusually occurred soon after the Tokachi-oki erathquake that took place on Sep. 26 2003 (MJMA 8.0). The unusual thermoactivities include (1) increase in gas flux, (2) weak glow witnessed by the high-sensitive camera in the nighttime with positions moving night by night, and (3) ash ejection of about 24m^3. Since the high-sensitive cameras can detect thermal radiation, the observed glow would be evidence for high-temperature of rock surface. It is considered that the Tokachi-oki earthquake would affect the volcano to eject a large amount of high-temperature gas, which resulted in the weak but unusual glow and ash deposits of the order of 10m^3 in volume.

著者

加藤 健二 都司 嘉宣

出版者

東京大学地震研究所

雑誌

東京大學地震研究所彙報 = Bulletin of the Earthquake Research Institute, University of Tokyo (ISSN:00408972)

巻号頁・発行日

vol.69, no.1-2, pp.39-66, 1994-09-30

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本研究では,1993年7月12日に発生した北海道南西沖地震(MUMA7.8)の津波の挙動を調べた.まず最初に,津波の初期条件を求めるために断層要素の決定を行なった.断層要素の決定は,余震分布,奥尻島での鉛直,および水平の地殻変動量および江差と岩内の検潮記録に基づいて行なった.余震分布から,断層面を北側,南側の2つからなるとした.その結果,南側の断層では,低角な東下がりのものと,高角な西下がりのものがともに奥尻島の地殻変動の条件を満たすことがわかった.ここで求めた断層要素を使って,断層は南北とも西下がりであるとして,北海道周辺での津波の振舞いを調べた.津波は,奥尻海脚,奥尻海盆の影響を受けて複雑な振舞いをしたことがわかった.また,奥尻島の南西部について詳しく調べてみると,奥尻海脚によって曲げられた津波が第1波を形成し,同島南部の初松前地区に集中して,ここの集落の家屋を全滅させたことがわかった.また,奥尻海脚の東端と西端を節とするここにトラップされた固有振動が,島南端の青苗の居住地の主要部に大きな被害をもたらす第2波を形成することがわかった.

著者

都司 嘉宣 日野 貴之

出版者

東京大学地震研究所

雑誌

東京大學地震研究所彙報 = Bulletin of the Earthquake Research Institute, University of Tokyo (ISSN:00408972)

巻号頁・発行日

vol.68, no.2, pp.91-176, 1993-09-30

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寛政4年4月1日(1792年)に,普賢岳の火山活動の終期に島原市付近に生じた地震に誘発された島原半島眉山の東斜面の崩壊によって,多量の土砂が有明海に流入し,有明海に大きな津波を生じた.この津波によって,島原半島側と,対岸の熊本県側の海岸は大きな津波被害を被った.近年,このときの熊本県側の津波被害の状況を伝える文書が数多く発掘された.この研究では,津波による死者数,家屋被害,田畑の浸水範囲と面積を確定し,あわせて被災現地での伝承,津波の浸水限界を示す「津波留石」などの知識を加えて,津波の浸水高の測定を行った.この津波による,肥後国の被害は,武士僧侶を除く死者が玉名郡で2,221人,飽田郡で1,166人,宇土郡で1,221人で肥後3郡合計で4,653人.このほかに武士僧侶とその家族たち162人を加え,4,815人が肥後三郡の死者総数となる.また,大矢野島を含む天草諸島では343人で,結局現在の熊本県がわ海岸全体で5,158人の死者があったものと見積られる.肥後三郡のけが人は811人,流失破損家屋2,252軒,浸水田畑3,848町歩であった.津波高さは熊本市の河内,塩屋,近津付近で15mから20mに達し,また三角半島北岸の細田,大田尾などで高く,三角町大田尾で22.5mに達した.

著者

Uyeshima Makoto Kinoshita Masataka Iino Hideaki Uyeda Seiya

出版者

東京大学地震研究所

雑誌

東京大學地震研究所彙報 = Bulletin of the Earthquake Research Institute, University of Tokyo (ISSN:00408972)

巻号頁・発行日

vol.64, no.4, pp.487-515, 1990-03-30

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The VAN-method for short-term earthquake prediction based on monitoring telluric potential changes, which has reportedly been successful in Greece, is now under testing in Japan. More than 20 local networks have been established and tested for about one year using existing electrodes and cables of the Nippon Telegraph and Telephone Corporation (NTT). Generally the records suffer from cultural noise much higher than in Greece, but some stations far from DC-powered rail-roads were found to be reasonably noise-free. Preliminary examination of data indicates that potential precursory signals in the sense of the VAN-method were recognized preceding earthquakes of M≧5 at some stations. This report presents an example, i.e. the possible correspondence between a specific type of telluric potential change appearing in the channel 2 at Teshikaga station, Hokkaido, and seismicity in the region off Kushiro, Hokkaido.

著者

音田 功

出版者

東京大学地震研究所

雑誌

東京大學地震研究所彙報 = Bulletin of the Earthquake Research Institute, University of Tokyo (ISSN:00408972)

巻号頁・発行日

vol.40, no.3, pp.613-623, 1962-11-30

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The Northern Miyagi Earthquake on April 30th, 1962 shook almost the same area as the Northern Rikuzen Earthquake on May 12th, 1900 with almost equal intensity The writer compared both earthquakes with one anothor and reached the following conclusions. Magnitude: The magnitude of the 1900 earthquake was larger than that of the later one by about two thirds, deduced by means of Kawasumi's method from the area of the isoseismals. The magnitudes Mk and M in the later one were deduced as 3.6 and 6.6, respectively (Fig. 2). Epicentre: The epicentre of the present one was determined in the neighbourhood of 38°45'N and 141°08'E, from the analysis of the record of the strong motion seismometer at Ishinomaki Weather Station. Therefore, that of the later one was about 20 km distance north from that of the previous one (Fig. 3). It was also ascertained that earthquakes seldom.occur in the northern part of Sendai Plain, although someone doubted its exsitence in that area. Number of after-shocks felt: Twenty-four after shocks were felt up to May 31st in the case of the former earthquake at Ishinomaki, while thirteen up to May 19th in the present earthquake. It was considered that this difference was caused by the dissimilar magnitute and epicentral distance from one another. Many abnormal after-shock were felt at the Hosokura Mine (Table III), compared with those felt at Ishinimaki (Table II) and Tsukidate (Table IV). Characteristics of the earthquake motion: The gravestones at Sekiun Shrine, Matsuyama Town, were studied. There were some gravestones which were rotated counterclockwise in the past earthquake, while such rotations of the gravestones could not be discerned in the case of the present one. It was inferred that this difference resulted from that of the epicentral distance and the magnitude.