著者

多田 堯

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.37, no.3, pp.407-415, 1984-09-25 (Released:2010-03-11)

参考文献数

28

被引用文献数

1 20

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The repeated triangulation surveys have revealed the conspicuous N-S extentional strain field in the central Kyusyu. This strain field has been caused by the horizontal crustal movement that the triangulation stations in both the sides of the Beppu-Shimabara Graben have moved away each others to the N-S direction. The Beppu-Shimabara Graben strikes across the central Kyusyu to the E-W direction. The gravity anomaly, the seismological data and other geotectonic data support the idea that the Beppu-Shimabara Graben is a rift of the crust and the north-eastern terminal part of the Okinawa Trough which is the active back arc basin of the Ryukyu Arc and is spreading to the N-S direction. Therefore, it is concluded that the N-S extentional crustal deformation in the central Kyusyu has been caused by the rifting and the spreading of the Okinawa Trough. In other words, the Kyusyu is rifting and spreading to the N-S direction along the Beppu-Shimabara Graben. The spreading ratio is estimated to be about 15mm/a from the horizontal crustal deformation.

著者

多田 堯

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.35, no.3, pp.427-433, 1982-09-25 (Released:2010-03-11)

参考文献数

2

被引用文献数

2

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An anomalous crustal uplift was observed at the west coast of Boso Peninsula. The crustal uplift began at the same time as the mining of mountain rock which began about ten years ago.It seems that the crustal uplift is the result of the elastic recovery deformation of the earth's crust caused by the man-made surface unloading.An elastic modulus of the uppermost earth's crust estimated by the total amounts of crustal uplift and mined rock is about 1-2×1011dyne/cm2.

著者

多田 堯

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.38, no.1, pp.1-12, 1985-03-25 (Released:2010-03-11)

参考文献数

15

被引用文献数

2 18

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The N-S extensional strain field in the Kyushu is understood as the result of the crustal deformation caused by the rifting and the spreading of the Okinawa Trough which crosses the Central Kyushu in the E-W direction. The spreading velocity and the spreading direction of the Okinawa Trough in the Kyushu have been estimated as 1.4cm/a and N-S direction, respectively, by the analysis of the distance survey. The horizontal and the vertical crustal movements, the normal active faults, the gravity anomaly, the volcanism, and the fault plane solutions of the earthquakes in the Shimabara Peninsula suggest that the Unzen Volcanic Graben is an active rift of the Okinawa Trough. The beginning of the spreading of the Okinawa Trough in the Kyushu has been estimated to be during the period from 0.8Ma to 0.5Ma B. P. by the spreading velocity and the width of the Unzen rift. The distributions of the active faults, the low gravity anomaly belts, the hypocenters of the shallow earthquakes and their fault plane solutions suggest that Okinawa Trough in the Kyushu consists of the three rifts whose strikes are E-W direction and the three transform faults like shear fault zones whose strikes are the NE-SW direction.

著者

池田 隆司 笠原 敬司 伊藤 健治 多田 堯

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.37, no.4, pp.549-557, 1984-12-25 (Released:2010-03-11)

参考文献数

4

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In order to obtain information on the underground structure around the Karasuyama-Sugaonuma fault, we carried out a temporary observation for artificial explosions which were blasted at four sites in Saitama and Ibaraki Prefectures in March 1982. Crossing the southern part of the fault, seven seismometers were deployed on an east-west striking observation line 30km long. For three of the explosions, good records were obtained at all the stations. Travel time analyses provided three layers; apparent p-wave velocities in the layers are 1.7km/sec, 2.8-3.1km/sec and 6.1km/sec from top to bottom. Travel times for the 6.1km/sec layer jump near Sashima-cho, Ibaraki Prefecture, where the western branch of the fault is supposed to lie. For the wave propagating through the topmost layer between the eastern and western sides of the north-south striking fault, a systematic difference in the wave form was observed. Those observed features strongly suggest that not only the basement layer (VP=6.1km/sec) but also upper layers are displaced or fractured by the Karasuyama-Sugaonuma fault.

著者

橋本 学 多田 堯

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.41, no.1, pp.29-38, 1988-03-25 (Released:2010-03-11)

参考文献数

22

被引用文献数

4 4

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Displacements and strains during the recent 80 years in Hokkaido are investigated by the analysis of triangulation or trilateration data. According to the distribution of displacements and strains, Hokkaido can be separated into three blocks, eastern, middle and southwestern Hokkaido.In eastern Hokkaido, northwestward displacements and NW-SE contractions are dominant before the 1973 Nemuro-Oki earthquake, while seaward displacements and EW extensions are detected after the event. Summing up them, westward displacements are left, which suggests westward sliding of the outer Kurile arc along the volcanic front and colliding at the Obihiro Tectonic Line [TADA and KIMURA (1987)].The Ishikari Low Land, which is considered to be a relic trench, may be the boundary between middle and southwestern Hokkaido along which E-W contractions are prevailing. This observation suggests that northern Honshu would not belong to the North American or the Okhotsk plate.Displacements associated with four major earthquakes which occurred during the period between the first and the last surveys are computed. Results show that the 1940 Shakotan-Oki earthquake may not give much influence on Hokkaido. Theoretical displacements computed by models for the 1952 Tokachi-Oki (M8.1) and 1968 Tokachi-Oki (M7.9) earthquakes are inconsistent with the observation, which may require re-analyses of data. The model for the 1973 Nemuro-Oki earthquake can predict the observed displacements qualitatively. The observed displacements are greater than the computed ones by a factor of two or three, which means that old triangulation surveys might suffer from scale errors.

著者

多田 堯

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.29, no.1, pp.47-53, 1976-03-10 (Released:2010-03-11)

参考文献数

10

被引用文献数

1 1

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The subcrustal structure beneath the Kanto plain was studied by geological and gravity data. Bouguer gravity anomalies were corrected by the thicknesses of the sedimentaly layers, and then Bouguer gravity anomalies were reduced to the basement. This correction coresponds to the Bouguer's correction.The reduced gravity anomaly represents the structure under the basement if the thicknesses of the sedimentaly layers are correct. But the depthes of the basements (the thicknesses of the sedimentaly layers) are not always so correctly measured that the reduced gravity anomalies will represent the structure beneath the basement and the structure of the basement as well.The reduced gravity anomaly map shows that the high gravity belt, or the anomalous gravity gradiant zone exists along the north side of the Tama-gawa river and the low garvity zone exists north side of the high gravity belt around the Sayama hill.These gravity anomalies also show that the geological tectonic line (the fault) lies along the north side of the Tama-gawa river with the drop in its north-east side near the Sayama hill. This fault passes the western part of Tokyo from north-west to south-east.

著者

大井田 徹 山田 功夫 多田 堯 伊藤 潔 杉山 公造 佐々木 嘉三

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.24, no.3, pp.240-247, 1971

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In order to study the seismic activity of microearthquakes in the southern part of the Neo Valley fault, an observation was carried out in 1968 from September 27 to November 2. Seven observing stations were set near the four stations of Inuyama Seismological Observatory.<br>About 400 microearthquakes were recorded during this observation, but about 50 epicenters could be determined. Their magnitudes were less than 2.<br>Microearthquakes occurred most frequently in the southwestern side of the fault, especially in the area upheaved by the Nobi earthquake of 1891. On the contrary, very few earthquakes occurred in the northeastern side. The focal depths of these shocks were very shallow.

著者

多田 堯 飯田 汲事

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.25, no.4, pp.295-301, 1973-03-30 (Released:2010-03-11)

参考文献数

13

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The relationships between the predominant period and the magnitude of the microearthquakes were studied. We assume the relationship in the following form. LogT=a+bM where, T is the predominant period in second and M is the earthquake magnitude. The following results were obtained, LogT=-1.50+0.50M (P wave, microearthquakes occurred in the vicinity of the Neo-Valley) LogT=-1.12+0.45M (S wave, microearthquakes occurred in the vicinity of the Neo-Valley) LogT=-1.38+0.44M (P wave, microearthquakes occurred in the vicinity of the Inuyama City) LogT=-2.03+0.65M (P wave, Matsushiro earthquake swarm) LogT=-1.45+0.40M (whole P wave). From the dislocation theory, the relation of T and M is derived as follows, LogT=-0.3-0.7 Logσ+0.5M. (1) where, σ is the stress drop in bar. Substituting σ=40 bars into (1), we get LogT=-1.4+0.5M. (2) This equation agrees well with the above mentioned results. But, when σ is not constant, the equation (1) suggests that the difference of the predominant period in the same earthquake magnitude is the differences of the stress drop. Indeed, the deviations of the data are so large that the stress drops seem to be not constant.The predominant periods of the Matsushiro earthquake swarm are shoter than those of the other microearthquakes. This evidence may relate to the characteristics of the Matsushiro earthquake swarm.

著者

多田 堯 橋本 学

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.41, no.2, pp.259-262, 1988-06-25 (Released:2010-03-11)

参考文献数

13

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A fault of the 1918 Omachi earthquake (M=6.5) have been estimated based on the vertical crustal movement associated with the earthquake. The 1918 Omachi earthquake was the largest earthquake which had ever occurred near the northern part of the Itoigawa-Shizuoka Tectonic Line (ISTL). The estimated fault is a high dip angle reverse fault with left lateral strike slip component. The fault plane strikes to the N-S and dips to the east. The fault model suggests a possibility that the Chikuma Mountains (Northeastern Japan) thrust against the Matsumoto Basin (Southwestern Japan).

著者

青木 治三 伊藤 潔 多田 堯 藤井 巌 山内 常生 伊神 煇

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.6, pp.1181-1194, 1970-11

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9月9日の岐阜地震は犬山地震観測所の北方約50kmに発生し,数多くの余震が観測された.震源の精度をあげるため予備観測および郡上郡奥明方村奥住小学校における10日間の余震観測を追加した.犬山観測網のDataにより9月20日より11月30日までの余震の分布を調査した.余震は主震の南東約3km地点を中心にとしNW-SE方向にのびる二次元の正規分布で近似できる.標準偏差は推定断層に垂直および平行な方向にそれぞれ2kmおよび4kmであった.この余震の中心は古生層,濃飛流紋岩の境界をなす構造線と一致し,観測された余震は主震に伴った断層がこの構造線により大きな残留歪を生じたことを示していると考えられる.|Since the earthquake of September 9, 1969 occurred at about 50km north of the Inuyama Seismological Observatory, a number of aftershocks were recorded at four recording stations: Inuyama, Sinpukuzi, Takazawasan and Ohira. It was intended immediately after the main shock to conduct a preliminary observation of damage and aftershocks for the estimation of the aftershock region and to find the best complementary recording site for the determination of hypocenters. During the two-day observation beginning Sep. 10, we could not find on the ground surface any sign of an earthquake fault. The observed P-S duration times however suggested that the depths of the aftershocks were very shallow.

著者

多田 堯

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.29, no.2, pp.117-126, 1976-05-15 (Released:2010-03-11)

参考文献数

17

被引用文献数

1

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A fault model of the 1974 Izu-Oki Earthquake was studied by the vertical crustal movement and the distribution of the after shocks.An assumed fault type is the right lateral pure strike slip, and the fault parameters are as follows, length=15km, width=8km, dip angle=75°, and dislocation=130cm.The stress field in the southern part of the Izu peninsula deduced from this fault motion is the north-south directional compressive field. This stress field represents that the Izu peninsula is compressed from south to north by the movement of the Philippine Sea Plate.