著者
大竹 政和
出版者
独立行政法人防災科学技術研究所
雑誌
防災科学技術 (ISSN:04541871)
巻号頁・発行日
vol.41, pp.1-7, 1980-11-25
被引用文献数
1

関東・東海地域はアジア・太平洋・フィリピン海の各プレートが会合する場所に当たり,3つのプレートの入り組んだ相互作用によって,そのテクトニクスはきわめて複雑な状況を呈している.そのために,地震の発生メカニズムについても不明の点があまりにも多い.しかし,わが国の心臓部を擁しかつ常に大地震の危険にさらされている地域であるだけに,この複雑な場の基本的な構造を解明することば,地震予知研究の立場から見ても第一級の研究課題と言わねばならない.幸い,深層地殻活動観測施設をはじめとする地震観測網の整備が進むに従って,この地域の震源決定精度が格段に向上し,小さな地震の発震機構も精度よく決めることができるようになってきた.こうした良質の地震データを基礎こ,関東・東海地域のテクトニクスを統一的に説明するモデルが生み出された.この統一モデルの概要を紹介し,あわせて,モデルから予測される関東直下の地震の発生メカニズムについて論ずることにしたい.
著者
尾池 和夫 山田 聡治
出版者
独立行政法人防災科学技術研究所
雑誌
防災科学技術研究所研究資料 (ISSN:0917057X)
巻号頁・発行日
vol.166, pp.161-175, 1995-03-31

The temporal variation of the number of LF and VLF noises has been compared with the occurrence of near shallow earthquakes. The results have been described by Oike et al.(1992), Oike and Murakami(1993) and Oike et al.(1993). In the case of 70 per cent of large earthquakes with magnitude larger than or equal to 6.0 anomalous increase of LF noises is observed within one day before the main shock whose epicentres are located in the land or shallow sea region. Similar phenomena are found in the case of near shallow earthquakes with magnitude larger than or equal to 5.0. Also inthe case of the largest earthquake (M7.8) during the observation a similar increase of LF and VLF noises as above mentioned was recorded. New observation system has been developed to record the wave forms of such phenomena and wave forms of co-seismic radiations from hypo-centers of large earthquakes. We have developed observation systems of electromagnetic radiations (EMR) related with the occurrence of earthquakes. Observing EMR at many and various observation points is important to detect EMR related with earthquakes. It is also important to observe them in low and wide frequency ranges for understanding the characteristics of the waves. We chose the ball antenna as a sensor which has sensitivity in low and wide frequency range (Ogawa et al., 1966). It is difficult to cover all frequency ranges by only one recorder, so we divided signals into several frequency bands and designed the most suitable filter and recording system for each band. We have developed handy observation system for EMR in the frequency range from 80Hz to 20kHz. Using this system, we can easily record EMR at any points and at any time. For example, going to the region where earthquake swarm is occurring, we can record EMR phenomena in the hypo-central region. Observation system for basic stations can record EMR in frequency range from DC to 20kHz broader than the handy system. By this system, we can get and make detailed analysis of records of EMR. By these two systems, we can expect to discuss EMR phenomena related with earthquakes. Such phenomena are possible to be caused by various mechanisms. It is also important to observe and analyze EMR from lightnings, because there is a possibility of the physical relationship between earthquakes and lightnings (Oike et al, 1993). During the observation using the developed recording systems the large earthquake of magnitude 7.8 occurred in the southwestern off Hokkaido region. Before and after the earthquake the anomalous increase of the number of LF and ELF noises were observed by the usual system and coseismic anomalous signals were recorded by the newly developed handy recording system.
著者
都司 嘉宣
出版者
独立行政法人防災科学技術研究所
雑誌
防災科学技術 (ISSN:04541871)
巻号頁・発行日
vol.35, pp.15-20, 1979-09-25
著者
村松 郁栄 小見波 正隆
出版者
独立行政法人防災科学技術研究所
雑誌
防災科学技術研究所研究資料 (ISSN:0917057X)
巻号頁・発行日
vol.155, pp.1-841, 1992-12
被引用文献数
1

1891年10月28日の濃尾地震の約1カ月後, 東京帝国大学総長の名で全国的なアンケート調査が行われ, 強震動と地震の破壊力が調べられた。全国の約1, 400市町村からの回答が各県知事名でまとめられて約1年後に彼の所に戻った。1891年の濃尾地震はマグニチュード8.0で, 日本の内陸における最大の地震であり, 世界でも最大級である。震源は極めて浅く, 中部日本に発生し, しかも人口の多い濃尾平野の近くに発生した。したがって, その地震動は色々な地盤における極限値を示すものと考えられ, その被害も多種多様である。例えば, 色々な池の寸法と応答についての質問があり, それらは現在の大型石油タンクに対応する。この回答集は強い地震動および耐震設計の研究にとっての宝庫であると思う。これらの回答の原文は毛筆で書かれ県ごとにまとめられている。それらは東京大学地震研究所に保管されている。故河角広地震研究所教授は, 丁寧に書かれたそれらの手書きのコピーを編者の1人に預けられた。彼は1977年から1984年にかけて, 岐阜大学その他の機関の助けを借りてこれらを活字印刷にした。さらに, 当時の市町村名と現在名とを対応させた表も作った。しかし, これらの印刷物は利用しにくいものであった。したがって, 編者らはこれらを1冊にまとめ, 当時の市町村の位置を1ないし0.5分(約1km)の精度の緯度・経度で表し(表3), 当時の郡境の県ごとの地図を作成した(図2)。また参考資料として, 回答地点の震度を現行気象庁震度で定め(表3), 震度分布図および回答中に報告されている諸現象と気象庁震度との対応表を付け加えた(図3および表4)。
著者
都司 嘉宣 白 雲燮 秋 教昇 安 希洙
出版者
独立行政法人防災科学技術研究所
雑誌
防災科学技術研究資料
巻号頁・発行日
vol.90, pp.1-96, 1985-01-14

At 12h00m, 26th May 1983, a large earthquake with magnitude 7.7 broke out off the coast of the Akita Prefecture, the north-east part of the Honshu Island, Japan. Accompanying with the earthquake a huge tsunami with height of 14 meters in maximum hit the coasts of Japan. Just 100 persons were killed due to the tsunami in Japan. About 90 minutes after the outbreaking of the earthquake, the tsunami reached to the east coast of the Korean Peninsula. Tsunami with inundation height of 5 meters was observed on Ullung Is. Tsunami also seriously attacked the mainland of Korea after 14h. Two fishermen were lost, and two persons were injured at Imwon Port. Wondok Town, Kangwon-do, where tsunami height of 3.6-4.0m was recorded, fishing boats rushed into the residential area, and a gas oil tank with volume of 130, 000 litters was carried by about 10 meter. One person was killed at Tonghae City. The amount of damage in the Republic of Korea is about 400 milion won (about 500 thousand US dollars). The initial movement of the sea level was upwards on the tide gauge records at Pusan. Ulsan, Mukho (Tonghae City), Sokch'o, and Chodong (Ullung Island), but only at P'ohang port downwards initial movement was recorded. The Kamuizaki-Oki Earthquake Tsunami of 1940-VIII-2 (M=7.5) also traversed the Japan Sea, and weaker tsunami with height of 0.5-2.0m recorded on the east coasts of the Korean Peninsula. Witnesses of this tsunami were newly discovered at Uljin Town, Kyongsang-Pukdo, and on Ullung Island, and tsunami of about 2 meters hit these places. The record of the Tsunami of the Kampo Earthquake (1741-VIII-29, M=7.5), which occurred off the south-west coast of Hokkaido Island and about 1, 500 persons were killed in Japan, was also newly discovered in the diary of the Choson Dynasty, and it was clarified that the tsunami hit the whole coasts of Kangwondo, where houses were swept and boats were destroyed. It is suggested that Yamato Rise, which is located in the center region of the Japan Sea, took a role of a lens on the propagation of these tsunamis. In the present paper the detailed report edited by Baek (1983) and studies on tsunamis and sea level anomalies made by Chu (1983) are introduced in chapters 2 and 3, respectively. Articles of the Nihonkai-Chubu Earthquake Tsunami on the Korean papers, and of historical earthquake tsunamis in old documents are mentioned in chapter 4 and 5, respectively. In chapter 6 old records of tidal waves are introduced.