Crustal Structure in the Western Part of Japan Derived from the Observation of the First and Second Kurayosi and the Hanabusa Explosions. : Part 2. Crustal Structure in the Western Part of Japan
利用統計を見る
Disaster Prevention Research Institute, Kyoto University
Osaka Institute of Technology
Gifu University
Geophysical Institute, University of Tokyo
National Science Museum.
抄録
By using data of the first and second Kurayosi and the Hanabusa explosions presented in Part 1, the crustal structure in the western part of Japan was derived. The velocity structure of the second layer with velocity 6.1 km/s was considered and the existence of the layer with velocity 6.4-6.6km/s was ascertained. On the travel time graph of the Kurayosi explosions, the phase with velocity 6.4-6.6 km/s gives clear first arrivals. Neglecting fluctuation of travel times due to inhomogeneity of the surface or within the crust, the trial was made to obtain the range of depth of boundaries as well as that of velocity whenever possible. From the interpretation of travel time graphs, two possibilities for the deeper part of crust, Model I and Model II, are given in Figs. 3 and 4. In Model I there is a gap of the Mohorovicic discontinuity west of Biwa Lake by about 4km and in Model II there is another layer with pretty high velocity 7.4-7.5 km/s above the layer with velocity 8.0-8.2km/s. The thickness of crust is quite different between the two models. The apparent velocity of 8.1 km/s was obtained pretty clearly.
第1部に与えられた第1回,第2回倉吉爆破および花房爆破の資料を用いて西部日本の地殻構造を求めた.良好な資料によつて6.1km/sの層の速度構造について考察する事が出来, 6.4～6.6km/sの層の存在が確かめられた.倉吉爆破では, 6.4～6.6km/sの位相が初動として明瞭に現れている.地表層や地殻内部の不均一性こ起因する走時の変動を表層の厚さを変える事によつて説明する事はやめて, 0.1秒程度の変動は考慮しなかつた.すべての記録の送り速度を揃えて震央距離順に並べ,位相の追跡の際に,肉眼による相関を行なつた.可能な場合には,境界面の深さおよび速度の範囲を求める様にし, 6.5km/sの層までは成功したが,深部の構造については,走時曲線の解釈によつてModel I, Model IIの2つになつた.従来のMohoと異り, Model Iでは,琵琶湖のやや西でMoho面に約4kmの食違いがあり, Model IIでは8.0～8.2km/sの層の上に7.4～7.5km/sの層があり,いづれがMohoか現在では断定出来ない.Moho面の探さもModel Iでは倉吉の下で約38km, Model IIでは7.4～7.5km/sの層の上の境界がMoho面とすれば倉吉の下で約25km, 8.0～8.2km/sの上の境界がMoho面ならば, 50kmとなる.また, 8.1km/sのみかけ速度が割合明瞭に得られた事は注意すべき事である.
雑誌名
東京大學地震研究所彙報 = Bulletin of the Earthquake Research Institute, University of Tokyo
巻
44
号
1
ページ
109 - 120
発行年
1966-07-25
ISSN
00408972
書誌レコードID
AN00162258
フォーマット
application/pdf
日本十進分類法
453
出版者
東京大学地震研究所
出版者別名
Earthquake Research Institute, University of Tokyo
アイテムへのリンクの際はタイトル右肩にある「Permalink」をご利用ください！
Please use "Permalink" at the top right of the title when linking to items!
Crustal Structure in the Western Part of Japan Derived from the Observation of the First and Second Kurayosi and the Hanabusa Explosions. : Part 2. Crustal Structure in the Western Part of Japan
ji0441006.pdf
(814.47KB)
