著者
宇佐美 龍夫 茅野 一郎
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.48, no.5, pp.923-933, 1970-12-05

The relation between Mk and MJ MJ=0.5Mk+4.35 is obtained by the method of least squares, using data from 1926 to 1943. It is shown that the relation can also be applied to earthquakes between 1885-1925. However, for earthquakes before 1885, the relation seems to hold for only large earthquakes with magnitude M(=0.5 Mk+4.85) larger than 8.0. MJ of the great Kanto earthquake of 1923 is given as 7.83 from the seismograms recorded at 3 Japanese stations.
著者
宇佐美 龍夫 茅野 一郎
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.48, no.5, pp.923-933, 1970-12-05

The relation between Mk and MJ MJ=0.5Mk+4.35 is obtained by the method of least squares, using data from 1926 to 1943. It is shown that the relation can also be applied to earthquakes between 1885-1925. However, for earthquakes before 1885, the relation seems to hold for only large earthquakes with magnitude M(=0.5 Mk+4.85) larger than 8.0. MJ of the great Kanto earthquake of 1923 is given as 7.83 from the seismograms recorded at 3 Japanese stations.
著者
宇佐美 龍夫
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.94, no.7, pp.656-664, 1986-01-25 (Released:2009-11-12)
参考文献数
6
著者
髙橋 利昌 浅野 彰洋 大内 泰志 川崎 真治 武村 雅之 神田 克久 宇佐美 龍夫
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.60, no.3, pp.193-217, 2008-02-15 (Released:2013-08-20)
参考文献数
40
被引用文献数
1

The major earthquakes of M=7 class, so-called Geiyo earthquake, have occurred in the subducted slab of the Philippine Sea plate under Aki-nada and Iyo-nada sea. The upper surface of the Philippine Sea plate is located in the depth from 40-45km in this region. Five Geiyo earthquakes can be found in 1649, 1686, 1857, 1905, and 2001 since 17th century. Magnitudes M of the older 4 events were larger than 7, while that of the last one is 6.7 in JMA (Japan Meteorological Agency) scale. Magnitudes and locations of focal regions of them were redetermined from seismic intensity data by the method of an attenuation curve fitting and of the seismic intensity inversion. Optimal magnitudes of old events were obtained between 6.7 to 6.9. This results show the old 4 events have almost the same magnitude as the 2001 event. One of the possible reasons why the former values were overestimated is that the empirical relation between magnitude and isoseismal area from inland shallow earthquakes was applied to determine the magnitude of the historical intraslab events such as Geiyo earthquakes.
著者
宇佐美龍夫
雑誌
日本の歴史地震史料 拾遺二
巻号頁・発行日
2002
被引用文献数
1
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.44, no.4, pp.1571-1622, 1967-03-31

Table of major earthquakes which occurred in and near Japan and accompanied by damages was prepared. The table consists of two parts, the major and auxiliary ones. Earthquakes in Formosa and Korea and outside Japan were omitted from these tables. The only exceptional one is the Chilean earthquake of May, 1960 which brought big damage to Japan.
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.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
宇佐美龍夫著
出版者
[宇佐美龍夫]
巻号頁・発行日
1986
著者
宇佐美 龍夫
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.5, no.3, pp.71-76, 1952-09-30 (Released:2010-03-11)
参考文献数
2

The reflection and refraction of plane SH waves incident upon a high-speed layer with a constant thickness d were studied. Numerical calculations were executed in a case when B1/B2=0.5507, μ2/μ1=3.25, and medium 1 and 3 are equal, and the results are given graphically. According to the results, the so-called total reflection is considered to be taken place when d/L≥5, and no plane SH waves can be propagated parallel to the discontinuous layer.
著者
宇佐美 龍夫 濱松 音蔵 久本 壮一 渡邊 健 中村 亮一 植竹 富一
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.45, no.3, pp.339-351, 1992-12-24 (Released:2010-03-11)
参考文献数
27

For the study of macroscopic characteristics of earthquake, it is necessary to investigate both historical and modern earthquakes from the same point of view. Historical earthquakes present informations on damages only. Modern earthquakes have various kind of data obtained from instrumental observations. Intensity data is common to both old and modern earthquakes. As the first step to study historical earthquakes, we studied the seismic intensity distribution of recent earthquakes, in the Tohoku district, which occurred in the interval from 1926 to 1990. Results are summarized as follows.(1) The isoseismal contours for many earthquakes off the Pacific coast elongate to north and south, and the seismic intensity decays steeply across the line which is almost parallel to the volcanic front. We call this line “Steeply Decay Line of Seismic Intensity (SDLSI)”. On the contrary, the distribution of seismic intensity for shallow inland earthquakes doesn't show this tendency.(2) We investigated the seismic intensity attenuation in the Tohoku district and obtained the next formula, I=A-BXwhere, I is the seismic intensity, X the hypocentral distance. Coefficients A and B are expressed as follows:for earthquakes of G1, G2 and G3 (see Fig. 2)A=0.198+0.679M, A/B=-1332+299.9M (east side of SDLSI), A=0.944+0.589M, A/B=-1329+279.5M (west side of SDLSI).for earthquakes of G4A=-1.315+0.912M, A/B=-410+134.9M(3) For the earthquakes along the plate boundary, we defined relatively low- and high-frequency earthquakes according to the value of MJ-MI, where MJ is JMA magnitude and MI the one determined by comparing observed intensity attenuation data of each earthquake with a curve calculated from formulas in (2). The epicenteral distribution of low- and high-frequency earthquakes does not show clear characteristics. But, off Fukushima Prefecture region, there seems to be a boundary of the high-and low-frequency earthquake's distribution along the plate boundary of about 40km depth. The high-frequency earthquakes are found in the west side of the boundary.
著者
宇佐美 龍夫 小竹 美子 佐藤 泰夫
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.22, no.4, pp.313-317, 1970-02-28 (Released:2010-03-11)
参考文献数
5

To make clear the features of the spectrum splitting due to the introduction of a soft solid core, the frequency and spectral amplitude of torsional oscillations are calculated for the modes with colatitudinal order number n from 2 to 9, assuming GUTENBERG-BULLEN A′ earth model. The only deviation from the G-B model is the assumption that the distribution of rigidity is constant in the core. The possibillity of estimating the rigidity of the core by the use of spectrum splitting was discussed.
著者
神田 克久 武村 雅之 宇佐美 龍夫
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.56, no.1, pp.39-57, 2003-06-02 (Released:2010-03-11)
参考文献数
30
被引用文献数
3

The method of the inversion analysis to evaluate the distribution of seismic energy radiated from an earthquake fault plane based on seismic intensity distribution data has been developed. The fault plane is divided into small sub-faults. The optimized seismic energy distribution of each sub-fault is calculated using the least square method to minimize the error between evaluated and observed seismic intensities.The energy distribution of a seismic fault is related to seismic intensity using the attenuation formula with equivalent hypocentral distance. The parameters of the attenuation formula are obtained from a regression analysis with measured seismic intensity data of recent moderate earthquakes.The forward analyses using an assumed model are performed to verify the accuracy of the inversion analysis and to evaluate the effect of factors such as the standard deviation of seismic intensity, constraint condition of inversion analysis and configuration of observation stations.Finally, the method is applied to the Showa Tonankai earthquake in 1944 and the Showa Nankai earthquake in 1946 and the result is compared with the tsunami and strong motion waveform inversion results to confirm the efficiency and applicability of the method.
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.