著者

湯村 哲男 広野 卓蔵 和達 清夫

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.23, no.2, pp.99-121, 1970-06-28 (Released:2010-03-11)

参考文献数

18

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Spatial distribution of earthquake foci for the period from 1926 to 1968 in and near Japan were expressed in 16 maps each for a layer of 20-40km in thickness lying between 0 to 600km in depth. The maps show definitely the boundary lines and centers of local activities distinguishable in seismicity from each other. We named them seismic blocks. The centers of the shallow seismic blocks which crowd in a zone along the west side of the Japan trench can be traced down to 600km in depth. At first such centers move with increasing depth toward two junction areas of the island arcs of Kuril, NE-Japan and Izu-Bonin, that is, the Hokkaido and the Kwanto districts. From there they continue sinking to north for Hokkaido and to west for Kwanto making a dipping angle of 30°. Then their directions change abruptly by 90° at a depth of about 300km. From North Hokkaido one branch of the locus of the center goes into the Okhotsk Sea and the other into the Japan Sea along the coast of Primorye. On the other hand, the locus of the block center moving toward the west Kwanto turns to the south at that depth under Gifu Pref. for the Shikoku Basin, although a shorter branch goes northward into the Japan Sea. It is notable that few deep shocks occur in the middle of the Japan Sea. Considering the other geophysical and geological phenomena such as (1) the negative zone of isostatic anomaly of gravity lying along the Japan trench branches out to the junction areas in land, (2) the movement of the triangulation stations for the last 60 years or so amounts to about 3m to the north at Aomori Pref. in comparison with the Kui Peninsula, showing that two forces are acting in the respective areas in opposite directions, (3) the axis of mountain ranges made of metamorphic rocks which encounter the locus of the block center in Hokkaido and Central Honshu underwent severer bending, we conclude that the locus of the seismic block center expresses the location of the mantle current coming from the Pacific. itself.

著者

和達 清夫

出版者

東京帝国大学地震研究所

雑誌

東京帝国大学地震研究所彙報 (ISSN:00408972)

巻号頁・発行日

vol.1, pp.55-58, 1926-10-15

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The pulsatory oscillations were observed at the seismologica observatory at Hommaru, Tokyo from Dec. 1st. 1925 to Jan. 21st. 1926. The Galitzin seismograph with photographic registration was used for the purpose. The pulsations observed at Tokyo may be classified into three sorts according to their periods: (A) those with a period shorter than 3 sec. (B) regular type with a period of 4-8 sec. and (C) irregular type with a period of more than 30 sec.

著者

和達 清夫 益田 クニモ

出版者

(公社)日本気象学会

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

vol.11, no.10, pp.444-454, 1933 (Released:2009-02-05)

参考文献数

6

被引用文献数

3

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This report is intended to give a complete table of travel times of earthquake waves such as P, S pP, PP, sS, SS, etc. especially taking the depth of focus into account. The calculation for the present table is based upon the results already obtained by us in the previous investigations on both near and distant earthquakes, whose epicente. s lie near the Japanese Islands. (Vol. 10, No.8, p. 460-474 and Vol. 11, No.1, p. 14-28 of this journal). This report is only a summarized one and the full text will be published in the Geophysical Magazine in the near future.

著者

和達 清夫

出版者

(公社)日本気象学会

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

vol.4, no.4, pp.83-86, 1926-07-28 (Released:2009-02-05)

著者

和達 清夫

出版者

(公社)日本気象学会

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

vol.10, no.9, pp.540-551, 1932 (Released:2009-02-05)

参考文献数

6

被引用文献数

1

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The velocity ratio of P and S waves is obtained by many authors to be nearly constant everywhere in the earth's crust. In the present investigatio_??_, is treated this problem by a method of tp-Tp-s diagram which gives the relation between the arrival time of P and duration of (P-S). Examining in many cases of large earthquakes of both shallow and deep origins occurred in our country, the relation is obtained to be approximately linear as is expected, especially in the cases of deep-seated earthquakes. From these investigations, the velocity ratio of P and S waves is obtained as about 1.73 in the upper part, it may be probably the so-called Mohorovicic layer, but its value seems to differ in different localities; while, in the deeper part nearly a constant value of 1.79 is obtained. Thus, using the result we are able to obtain the depth of seismic focus by a simple method, especially in case of deep-seated earthquakes.

著者

和達 清夫

出版者

(公社)日本気象学会

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

vol.12, no.9, pp.496-497, 1934 (Released:2009-02-05)

参考文献数

5

著者

和達 清夫 高橋 末雄

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.27, no.1, pp.42-56, 1974-03-30 (Released:2010-03-11)

参考文献数

23

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In the present paper the underground structure peculiar to Japan and its neighborhood is dealt with, based on the seismic activity in Japan and neighborhood, especially taking account of the fact that each of the seismic activity area and the seismic inactivity area shows in the subterranean space its respective space, and adding the authors' investigational result to the fruits of researches hitherto.Main results of the present paper are:(1) The seismic activity area was divided into 3 zones: the shallow earthquake zone (particularly the existence of “a thick shallow earthquake zone”), the joint earthquake zone and the deep earthquake zone.(2) A concept that the seismic activity zone can be regarded as “the crust” has been proposed.(3) From the discussion of the travel time residual and the area of abnormal distribution of seismic intensities, the values of Low V and Low Q of the seismic inactivity area were obtained, and in particular the stronger point of that property was found at a comparatively small depth in the underground on the continental side along the volcanic front.(4) The mantle flow in Japan and neighborhood is assumed to be composed of its main flow (along the deep earthquake zone) which flows descending from the Pacific side to the continental side and from east to west, of a weak flow northward in the offing of Tosa and in Enshu-nada, and of flows eastward and southward from the direction of the Sea of Japan.(5) In general, where the mantle flow ascends, there exist Low V and Low Q and the area is related to volcanic activities, and where the flow descends, the area is related to the seismic activity area.(6) The joint earthquake zone is an area of the strongest seismic activity, and is closely related with large-scale earthquakes.