著者

行武 毅

出版者

東京大学地震研究所

雑誌

地震研究所彙報別冊 (ISSN:09150862)

巻号頁・発行日

vol.8, pp.71-81, 1992-09-30

---

地震研究所における地震予知研究 : 現状と将来展望

著者

武尾 実 三上 直也

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.65, no.3, pp.p541-569, 1990-12

被引用文献数

4

---

Detailed rupture processes of six intraplate earthquakes in Japan, the 1961 Kitamino earthquake, the 1969 GifuKen-Chubu earthquake, the 1974 Izu-Hanto-Oki earthquake, the 1975 OitaKen-Chubu earthquake, the 1980 Izu-Hanto-Toho-Oki earthquake, and the 1984 NaganoKen-Seibu earthquake, are compiled and compared to each other to make clear common features of an earthquake rupture process. The rupture processes are obtained by waveform inversion using strong motion seismograms in previous studies. Five of these rupture processes are also compared with distributions of precisely determined aftershocks. Earthquakes with relatively smooth rupture propagation, such as the 1974 Izu-Hanto-Oki earthquake and the 1961 Kitamino earthquake, represent smoother slip distribution than earthquakes with relatively irregular rupture propagation, such as the 1969 GifuKen-Chubu earthquake and the 1980 Izu-Hanto-Toho-Oki earthquake. It is also recognized that aftershocks of magnitude greater than 4 do not occur in the large slip area. Most large aftershocks take place near the edge of the large slip region and in the small slip region. Aftershocks also tend to cluster near the edge of the large slip region. These results are very consistent with numerical experiments of dynamic rupture, so it is suggested that the relation between aftershocks and coseismic slip pattern obtained in this paper hold generally for earthquake rupture processes. A clear delay of rupture propagation occurs in the large slip area during the 1969 GifuKen-Chubu earthquake: on the other hand, the small slip area in the 1980 Izu-Hanto-Toho-Oki earthquake is characterized by a deceleration of rupture propagation. The large slip area in the former case is interpreted as a barrier which resisted fracturing at first and was broken with a high stress drop. In the latter case, mechanical weakness due to volcanic structure located around the source region, seems to have affected the rupture process. A similar geological condition may have affected the rupture process of the 1978 Izu-Oshima-Kinkai earthquake which occurred about 10 km south of the 1980 Izu-Hanto-Toho-Oki earthquake.日本内陸で発生した6つの地震について,詳細な破壊過程を取りまとめ,それらの相互の特徴及び余震分布との対応等を調べた.取り上げた地震は1961年北美濃地震・1969年岐阜県中部地震・1974年伊豆半島沖地震・1975年大分県中部地震・1980年伊豆半島東方沖地震及び1984年長野県西部地震である.これらの地震については,震源近くで記録された強震計記録の波形インバージョンにより,詳細な破壊過程が解明されている.

著者

茂木 清夫

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.47, no.3, pp.419-427, 1969-06

---

Monthly distributions of small and large earthquakes in the Japanese region are discussed based on recent seismic data. Smaller earthquakes do not show any systematic annual variations. But large earthquakes with magnitude 7.5 and over occurred concentratively in some limited seasons and the active season is different in the two adjacent active regions. This regularity of large earthquakes in the Japanese region is confirmed by historical earthquake data. Regarding all the large earthquakes in the Northern and the Southern Hemispheres, no systematic annual variations can be concluded. This is not inconsistent with the above-mentioned regional regularity.|地震の頻度が季節変化を示すということが大森やDavison,その他の多くの人によって報告されているが,近年この問題を論じたものはほとんどみられない.この問題を論ずるには,信頼すべき資料にもとづいて,適切な解析を行うことが重要であるので,最近の高精度の地震資料によって再検討を加えることは有意義である.今回の結果によると,大森やDavisonらの指摘した規則性は認められないが,日本付近の大地震について,極めて著しい季節的集中性があることが見出された.要約すると,1.日本各地の小さい地震については,一般に,有意な季節変化は認められない.2.1920年以降のM7.5以上の大きい地震は特定の季節にのみ集中して起こる傾向がみられる.この傾向は,1600から1919までの大地震(M7.9以上)についても認められ,その集中性は統計的に有意である.その活動の季節は場所によってちがい,大きい地震は,北海道・三陸の太平洋側沖合では2月から5月まで,とくに3月に集中し,宮城県沖から関東・東南海道にかけては9月から1月まで,とくに12月に集中して起こった.3.世界中の大きい地震については,南北両半球の大きい地震がとくに夏に多いという規則性(Davisonによる)は認められない.

著者

Uyeda Seiya Watanabe Teruhiko Ozasayama Yoji Ibaragi K.

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.55, no.1, pp.55-74, 1980-08-25

---

Results of terrestrial heat flow measurements in Peru and Ecuador conducted in 1969, are reported. Eight different sites in Peru and one site in Ecuador were visited for underground temperature measurement. However, data from only five metal mines in Peru and the metal exploration site in Ecuador were usable. The geothermal gradient data on four oil fields in Peru and two in Ecuador were referenced. Although high heat flow has been indicated on the continent side of the Andes (the Gasapalca and the Guajone mines and the Ucayali oil field), low geothermal gradients were also found in mines in high Andes (the Raura and Cerro Verde mines). The latter are suspected to be the result of ground water circulation. The highly disturbed cases of the Morococha and San Vicente mines showed almost zero gradient. Much more work is needed to delineate the regional heat flow pattern of the area.

著者

纐纈 一起 鷹野 澄 坪井 誠司 宮武 隆 阿部 勝征 萩原 幸男

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.64, no.4, pp.517-532, 1990-03-30

---

地震予知計画の下で国立大学により運営されてきた地震予知観測情報ネットワークでは,各構成機関により維持・管理されている約160点の地震観測点の波形データが,全国7箇所の地域センター等に集められ,そこでそれぞれ独自に開発された自動処理システムにより,地震波到着時刻の読み取り・震源位置の決定などがリアルタイムで行なわれている.この処理結果はオンラインで地震研究所の地震予知観測情報センター(EPDCに転送され,リアルタイム地震データとしてデータベースに保存されている.EPDCではこのデータを統合し,TSSにより表示できるようにしたシステムを開発した.統合処理は2つのジョブが前処理と本処理を担当する.前処理ではデータを震源時順に並べ替えることと,震源時と震央座標が近い地震を同一地震と仮判定することが行なわれる.この結果がさらに本処理に送られ,親子法による同一地震の本判定と震源再決定が実行される.震源再決定で得られた統合処理結果は,ユーザのTSSごとに起動される検索プログラムで表示させることができる.1ヵ月間の処理結果を気象庁の震源速報と比較したところ,海の地震の深さが異なるのが目立つ程度で,マグニチュード3半ばより大きい地震はよく一致した.それより小さな地震では全般的に気象庁より検知能力が高いが,観測網が粗い中国・四国地方やまったく観測点がない九州地方は気象庁が優れている.本システムの今後の課題は,現在大きな地震のデータ統合を優先しているため,小さい地震の分離能力が弱い点を改善することである.また,現在情報不足で困難となっているマグニチュードの独自決定も課題であろう.

著者

Miyake Hiroe Koketsu Kazuki Kobayashi Reiji Tanaka Yasuhisa Ikegami Yasushi

出版者

東京大学地震研究所

雑誌

地震研究所彙報 (ISSN:00408982)

巻号頁・発行日

vol.81, no.3/4, pp.267-272, 2006

---

The Tokyo metropolitan area is under constant threat of strong ground motions from future plate-boundary earthquakes along the subducting Philippine sea slab. Here, we upgrade a ground motion simulation of the 1923 Kanto earthquake using a source model along the new geometry of the Philippine sea slab, geophysical-based velocity model, and effcient computational tool. The source process was inferred from strong-motion, teleseismic, and geodetic data with the new geometry of the slab. The 3D velocity-structure model beneath the Tokyo metropolitan area has been constructed using integrating refraction, reflection, borehole, microtremor, and gravity data, as well as ground motion spectra. We introduce a low-frequency ground motion simulation using these models and the finite element method with a voxel mesh. The western basin edge complicated wave propagation, and excited long-period motions were found within the basin. We confirmed that the simulated ground motions are sensitive to the distribution of asperities of the source model along the shallower plate geometry where the eastern major asperity is located closer to downtown Tokyo than in previous models. Because high-frequency components are essential for seismic intensity measurements, source modeling using the pseudo-dynamic approach and ground-motion simulation using the hybrid method combining deterministic and stochastic approaches are strong candidates to complete a broadband ground motion simulation.

著者

大堀 道広 纐纈 一起 南 忠夫

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.65, no.2, pp.433-461, 1990-09-28

---

本論文は,不整形地盤の3次元問題について,解析手法を提案し,さらにこれを用いて堆積盆地の地震動特性の検討を行ったものである.まず, 2次元問題において不整形地盤を解析するための有力な手法と評価されているAL法を, 3次元問題への拡張するための定式化を行った.従来AL法による3次元解析では特に工学的に重要な平面S波入射の垂直入射問題を取り扱うことが困難とされていた.この問題を,ベクトル・ポテンシャルによる変位の表現式を工夫することにより解決した.そして,提案した解析手法の妥当性と作成したプログラムの信頼性を確認するために,他の手法により示されている軸対称堆積盆地についての解析結果と比較したところ,良い一致を示した.続いて,これまで取り扱われることの少なかった3次元地下構造を有する堆積盆地の地震動特性を,軸対称問題ばかりでなく,非軸対称問題についてもAL法による3次元解析を行い,得られた周波数応答および時刻歴応答を1次元解析および2次元解析による応答と比較検討した.その結果, 1次元解析よりも2次元解析, 2次元解析よりも3次元解析というように,解析する次元が高くなるにつれて,堆積盆地の地表動には,より短周期の波動が励起され,振幅もより大きくなり,継続時間もより長くなるという傾向が見られた.これは, 3次元的な地下構造が地震動に与える影響が非常に大きいことを示唆している.

著者

Kobayashi Ryoji Koketsu Kazuki

出版者

東京大学地震研究所

雑誌

地震研究所彙報 (ISSN:00408973)

巻号頁・発行日

vol.81, no.3/4, 2006

著者

Takeo Minoru Mikami Naoya

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.65, no.3, pp.541-569, 1990-12-25

---

Detailed rupture processes of six intraplate earthquakes in Japan, the 1961 Kitamino earthquake, the 1969 GifuKen-Chubu earthquake, the 1974 Izu-Hanto-Oki earthquake, the 1975 OitaKen-Chubu earthquake, the 1980 Izu-Hanto-Toho-Oki earthquake, and the 1984 NaganoKen-Seibu earthquake, are compiled and compared to each other to make clear common features of an earthquake rupture process. The rupture processes are obtained by waveform inversion using strong motion seismograms in previous studies. Five of these rupture processes are also compared with distributions of precisely determined aftershocks. Earthquakes with relatively smooth rupture propagation, such as the 1974 Izu-Hanto-Oki earthquake and the 1961 Kitamino earthquake, represent smoother slip distribution than earthquakes with relatively irregular rupture propagation, such as the 1969 GifuKen-Chubu earthquake and the 1980 Izu-Hanto-Toho-Oki earthquake. It is also recognized that aftershocks of magnitude greater than 4 do not occur in the large slip area. Most large aftershocks take place near the edge of the large slip region and in the small slip region. Aftershocks also tend to cluster near the edge of the large slip region. These results are very consistent with numerical experiments of dynamic rupture, so it is suggested that the relation between aftershocks and coseismic slip pattern obtained in this paper hold generally for earthquake rupture processes. A clear delay of rupture propagation occurs in the large slip area during the 1969 GifuKen-Chubu earthquake: on the other hand, the small slip area in the 1980 Izu-Hanto-Toho-Oki earthquake is characterized by a deceleration of rupture propagation. The large slip area in the former case is interpreted as a barrier which resisted fracturing at first and was broken with a high stress drop. In the latter case, mechanical weakness due to volcanic structure located around the source region, seems to have affected the rupture process. A similar geological condition may have affected the rupture process of the 1978 Izu-Oshima-Kinkai earthquake which occurred about 10 km south of the 1980 Izu-Hanto-Toho-Oki earthquake.

著者

宇佐美 龍夫 浅野 潤三

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.47, no.2, pp.271-394, 1969-07-31

---

A bibliography of field studies on major earthquakes in Japan was prepared. This includes papers concerning the field inspection, seismometrical study, study of related phenomena and investigation on damages which were published before the end of 1965. The list consists of the following items: (1)reference number (2)author's name (3)title of the paper (4)name, volume, year and page of Bulletin in which the paper is published or name of publishers (5)name and year of earthquake studied (6)main subject Date, name, latitude, longitude, focal depth, magnitude and reference number of earthquakes are arranged in another table. Papers are classified by the year of earthquake and main subject and arranged in a form of table.

著者

宇佐美 龍夫

出版者

東京大学地震研究所

雑誌

地震研究所研究速報

巻号頁・発行日

vol.12, pp.1-29, 1974-03

---

Referring to the damage and intensity distributions and the tsunami-attacked areas and Comparing them with recent earthquakes in the same region, the epicenter location of Japanese historical earthquakes accompanied by damages were re-examined. Existence range of epicenters were also given. Earthquakes from 416 A. D through 1925 are considered. For those after 1926, accurate epicenters are given by the Japan Meteorological Agency and especially since 1960, standard deviation of epicenters are also given by J.M.A. The results are arranged in the form of descriptive tables and figures.

著者

Fukao Yoshio Kono Masaru Yamamoto Akihiko Saito Matsuhiko Nawa Kazunari Giesecke Alberto Perales Crisolfo

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.74, no.2, pp.161-266, 2000-03-21

---

We collected all the data of gravity measurements carried out over the last 40 years by Institute Geofisico del Peru (IGP). Because of the long time since data collection, some of the information needed for data reduction were lost over the years. This loss made it difficult for us to determine all of the gravity values unambiguously and consistently from the presently available IGP data alone. Accordingly, there was a need for independently determined gravity stations to which the measurements done by IGP may be compared. In order to provide reference gravity values, we utilized Japanese survey data collected between 1980 and 1984, and conducted more surveys in various parts of Peru in the period between 1995 and 1998. These gravity stations number more than 800, and provide three or more reference points for each of the IGP survey routes. Using these references, the gravity values were calculated for the IGP dataset and Bouguer corrections were applied. Finally, a Bouguer anomaly map of Peru was produced based on these data. This paper reports all the procedures involved in the data reduction, discusses the reliability of the reduced data, and points out the main features of the Bouguer anomaly map.

著者

溝上 恵

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.55, no.2, pp.483-504, 1980-11-15

---

It has been pointed out from geological and geomorphological evidences that the time rate of undulatory crustal movement shows a remarkable dependence on its wavelength. Specific studies on the problem were made by MATSUDA (1960, 1961, 1964), KAIZUKA (1967, 1968) and OTA (1968, 1969). KAIZUKA compared the rate of folding in the Quaternary with the mode of undulatory crustal movements in the present. He indicated such regularities of folding as the smaller the wavelength, the greater the rate of folding and the rate of present folding is in the same order with that of the Quaternary folding.

著者

飯高 隆 中村 功 溝上 恵

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.64, no.1, pp.37-50, 1989-06-30

---

関東地方においては,これまでに地震波速度構造の不均質性について様々な研究がなされてきた.これらの研究の結果,太平洋プレート,フィリピン海プレートの沈み込みが示された.このように複雑な構造をした地域において,沈み込むプレートの形状を求めることは,大変重要なことである.東京大学地震研究所の日立(HIT)の観測点の地震波記録で,P波とS波の間に立ち上がりのはっきりした後続波が見られた.この研究では,この後続波が,沈み込む太平洋プレート上面でPS変換された波であることを明らかにし,この変換波を用いて沈み込む太平洋プレート上面の深さを求めた.このように変換波を用いる方法は,プレート上面の深さを求めるのに有効であることが知られている.この研究において,関東地方下で求められた太平洋プレート上面は,日立の観測点下で約60kmの深さに求まり,その面は2重深発面の上面にほぼ一致した.また,この深さはS波の反射から求められた結果(小原,1987)と矛盾しない.

著者

溝上 恵

出版者

東京大学地震研究所

雑誌

地震研究所研究速報

巻号頁・発行日

vol.12, pp.41-56, 1974-03

---

It should be emphasized that when using an array to determine directly dT/dΔ for the study of the structure of the Earth's deep interior, the necessity for the correction for the near surface structures is inevitable, particularly in such a region as the Kii Peninsula where existence of a dipping Moho-discontinuity is expected. A teleseismic slowness vector analysis method given by Zengeni(1970) is applied for the study of the diwing Moho-discontinuity in the Kii Peninsula.

著者

雑賀 敦 平松 良浩 大井田 徹 山岡 耕春

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.75-86, 2001-07-25

---

Spatial and temporal variations in seismic anisotropy in the crust are investigated using earthquakes in the crust and at the upper boundary of the subducting Philippine Sea plate in the Tokai region, central Japan. We use waveform data from December 1986 to August 1999 recorded by the micro-earthquake observation network of the Research Center for Seismology and Volcanology, Nagoya University. The method of Silver and Chan (1991) is applied to evaluate splitting parameters, a leading shear-wave polarized direction and a delay between two polarized waves. A total of 362 high-quality waveform data within the incident angle of 35° are analyzed in this study. The leading shear-wave polarized directions are approximately E-W, in spite of differences of focal depths. This direction is consistent with the direction of regional horizontal maximum compressive stress in the Tokai region reported before. The time delay increases in proportion to the focal depth. These results indicate that the regional compressive stress controls anisotropy not only in the upper crust but also in the lower crust. Assuming the uniform distribution of anisotropy, the degree of anisotropy is estimated to be 0.5% in the lower crust. An increase in time delays between two-polarized waves is found before and after the Aichi-ken Tobu earthquake (M = 5.7) in 1997 at the station STN. This variation is statistically significant with the confidence level of 99.999% and is not an apparent change due to a variation in hypocenter distribution. No temporal variation of splitting parameters is found at the station INU. These results can be explained by a change of the volumetric and areal strain in the most-upper part of the crust due to the postseismic slip of the Aichi-ken Tobu earthquake.

著者

高橋 龍太郎

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 (ISSN:00408972)

巻号頁・発行日

vol.29, no.1, pp.71-95, 1951-06-25

---

Assuming that tsunami activity recorded during historic times is still continuing at present and will continue also in the future, the writer has estimated the degree of danger of tsunami for each village on the Pacific coast of Japan which may be expected in the future. Results are given in Fig. 2 and in Table III.

著者

Hatori Tokutaro

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.47, no.6, pp.1063-1072, 1969-12-20

---

The wave source of the tsunami generated off West Hokkaido (Shakotan Peninsula), in the Japan Sea, on Aug. 2, 1940 is estimated by means of an inverse refraction diagram, making use of a new bathymetric chart. The source area extends 170km in the NNW-SSE direction, which is smaller than that obtained by Miyabe (1941). However, the dimension estimated by the present analysis is still large for the earthquake magnitude of M=7.0. From a comparison of the geographic distribution of the earthquake intensity with those of the other tsunamigenic earthquakes that occurred in the Japan Sea, the magnitude of this earthquake is investigated. Effective tsunami height observed on the surrounding coasts of the Japan Sea can be explained by the direction of the present source. Magnitude of the tsunami of 1940 seems to be equal to that of the Niigata tsunami of 1964 and is represented as m=2. Besides, the wave source of the tsunami generated off Rumoi, West Hokkaido, on Nov. 4, 1947 is discussed, taking the aftershock area into consideration.|1940年8月2日,北海道積丹沖に起きた津波は日本海全域に伝播し,北海道西岸をはじめソ連の沿海州と北朝詳,隠岐にも家屋,船舶などに被害を与えた,地震の規模Mは,気象庁の地震カタログ(1958)によるとM=7.0, USCGSによるとMG=7.7と示されており,両者の決定値には著しい違いがある.一方,余震は札幌において多数観測され,P-S頻度分布は10 secから33 secの範囲にあつて,余震域の長さは約190kmと推定されている(宇津,1961)

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 (ISSN:00408972)

巻号頁・発行日

vol.36, no.2, pp.99-134, 1958-07-23

---

噴火の際に火山周辺の地殻が著しく変動することは,古く1910年の有珠山の噴火の場合に大森博士によつて精密水準測泣が行われて以来,主な噴火について同様の測量が実施されて,次第に明らかになつて来た.これらの火山周辺の地殻変動に関する研究は必ずしも少なくないけれども,火山の噴火の機構との関係としてその火山学的意味を吟味したものはほとんど見られない.本論文ではこれまでに得られた測量の結果を調べて地殻変動の特性及び,噴火現象との関係を明らかにすることを試みた.

著者

半田 駿

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.73, no.3/4, pp.345-359, 1999-03-29

---

The MT survey was conducted to clarify the lower crustal resistivity structure beneath the volcanoes of Tsurumi- and Yufu-Dake in central Kyushu, SW Japan. The 2-D resistivity model obtained reveals that the highly resistive lower crust lies under highly conductive layers with a thickness of about 3 km at a shallow part of the crust. Since the resistive lower crust is also found in the Aso Volcano area, the present result implies that the lower crust is commonly resistive beneath volcanoes of the volcanic front in central Kyushu, while conductive layers are found at the middle and lower crust beneath the volcanic zone in many subduction zones, as seen in NE Japan.