{"created":"2021-03-01T06:53:11.827214+00:00","id":34315,"links":{},"metadata":{"_buckets":{"deposit":"aa316f47-a751-4c17-8b8b-f92ace4f6157"},"_deposit":{"id":"34315","owner":"1","owners":[],"pid":{"revision_id":0,"type":"depid","value":"34315"},"status":"published"},"_oai":{"id":"oai:repository.dl.itc.u-tokyo.ac.jp:00034315","sets":["80:4535:5119:5120","9:504:4538:5121:5122"]},"author_link":["133416","133415"],"item_4_alternative_title_1":{"attribute_name":"その他のタイトル","attribute_value_mlt":[{"subitem_alternative_title":"4. On the Coda Waves of Earthquake Motions(Part 3)"}]},"item_4_biblio_info_7":{"attribute_name":"書誌情報","attribute_value_mlt":[{"bibliographicIssueDates":{"bibliographicIssueDate":"1947-02-28","bibliographicIssueDateType":"Issued"},"bibliographicIssueNumber":"1-4","bibliographicPageEnd":"78","bibliographicPageStart":"47","bibliographicVolumeNumber":"23","bibliographic_titles":[{"bibliographic_title":"東京帝國大學地震研究所彙報 = Bulletin of the Earthquake Research Institute, Tokyo Imperial University"}]}]},"item_4_description_13":{"attribute_name":"フォーマット","attribute_value_mlt":[{"subitem_description":"application/pdf","subitem_description_type":"Other"}]},"item_4_description_5":{"attribute_name":"抄録","attribute_value_mlt":[{"subitem_description":"Chapter 4. The coda periods of extremely distant earthquakes. 1). In this Chapter, investigations have been made of the coda oscillations of extremely distant earthquakes recorded in Tokyo. Since these earthquake records were obtained by a horizontal pendulum type seismograph, with long. oscillation period of about sixty seconds, they can be regarde as representing nearly exactly the true earth movements during earthquakes. The epicentral distances of the earthquakes studied in this Chapter exceeded 10,000km, their epicenters being distributed along the western margins of the Nor h and South American continents. 2). The frequency distributions of various periods of coda waves of four selected distant earthquakes are shown in Figs.2-5, while the successive one minute means of the periods of thirteen earthquakes in Figs.6-17. The predominant periods of the coda oscillations of the respective earthquakes determined by these diagrams are given in Table IV. The predominant ,period in the case of the Mexico earthduake of Dec. 23, 1937 which is the nearest earthquake studied in this Chapter, with an epicentral distance of 11600km, has been found to be 17.5±0.13 seconds, while that of the South Georgia earthquake of Jan. 24, 1938, the most distant one, with an epicentral distance of 18,000km, has been found to be 18.1±0.16 seconds. It is likely that the greater the epicentral distances, the longer are the predominant periods, and the smaller the distances, the shorter the periods ; a conclusion which agrees with that arrived at for the nearer earthquakes describedin Chapters 1 to 3. The relation between the predominant periods and \\ the epicentral distances is shown by a curve in Fig.18. This curve indicatesthat, as the epicentral distance increases, the predominant period also increases but not with the same rate. The rate of increase of the predominant period according to the epicentral distance becomes smaller and smaller and, if the epicentral distance exceeds 13,000km, the predominant period no longer increases but remains almost constant. 3). In the case of the earthquakes studied in the preceeding Chapters, of which the epicentral distances were less than 10,000km, it was found that after the large surface waves, which have been propagated along the minor arc of the earth's surface died away, the earthquake motions usually become almost constant in period and remained so during the subsequent 30 or 50 minutes. These regular waves, however, are followed again by large waves with longer periods, which are presumably the surface waves propagated along the major arc of the earth's surface. But after these large surface waves passed over, no wave due to the earthquake motion is seen on the seismogram any longer. But if an earthquake of great magnitude is observed at a great distance of more than 10,000 km from the epicentre, as in our present case, the earth's oscillation is found to differ somewhat from these observed in a smaller earthquake. On the seismogram of such a great earthquake, the oscillation is found to continue for two hours or more, and even after the large surface waves that have been propagated along the major arc of the earth's surface have passed over, the waves with pretty uniform periods and small amplitudes are seen to continue .for more than 30 or 40 minutes. This part of coda oscillations, which follows the surface waves along the major arc of the earth's surface was named in this paper the second part cf the coda oscillation. In contrast to this the coda oscillation that follows the surface waves along the minor arc of the earth's surface was named the first part of the coda oscillation. The coda waves studied in the preceeding Chapters therefore exclusively concerned with this first part. 4). Detailed studies on the second part of coda waves of four selected earthquakes have revealed that the predominant periods of this part of oscillations are about 16 seconds in all of them, in spite of the difference in their epicentral distances. The important conclusion derived from this fact is that quite likely this constant predominant period of this p rt of coda waves is the free oscillation period of the surface layer of the earth's crust on which the observation station is situated. In other words, the coda oscillations of a great earthquake composed, in their extremely later portions of the free oscillations of the surface layer. If we assume that the mode of oscillations of the surface layer to be like what was proposed by E. Wiechet, the period T of its free oscillation is given by T=4 H/V, where H is the thickness of the surface layer concerned, and V the velocity of the transversal wave within it. If the velocity of the transversal wave is taken as V=1.14km/s, the superficial layer bocomes about 4.5km in its thickness.","subitem_description_type":"Abstract"}]},"item_4_full_name_3":{"attribute_name":"著者別名","attribute_value_mlt":[{"nameIdentifiers":[{"nameIdentifier":"133416","nameIdentifierScheme":"WEKO"}],"names":[{"name":"Omote, Syun'itiro"}]}]},"item_4_identifier_registration":{"attribute_name":"ID登録","attribute_value_mlt":[{"subitem_identifier_reg_text":"10.15083/0000034315","subitem_identifier_reg_type":"JaLC"}]},"item_4_publisher_20":{"attribute_name":"出版者","attribute_value_mlt":[{"subitem_publisher":"東京帝国大学地震研究所"}]},"item_4_source_id_10":{"attribute_name":"書誌レコードID","attribute_value_mlt":[{"subitem_source_identifier":"AN00029699","subitem_source_identifier_type":"NCID"}]},"item_4_source_id_8":{"attribute_name":"ISSN","attribute_value_mlt":[{"subitem_source_identifier":"00408972","subitem_source_identifier_type":"ISSN"}]},"item_4_subject_15":{"attribute_name":"日本十進分類法","attribute_value_mlt":[{"subitem_subject":"453","subitem_subject_scheme":"NDC"}]},"item_4_text_21":{"attribute_name":"出版者別名","attribute_value_mlt":[{"subitem_text_value":"Earthquake Research Institute, Tokyo Imperial University"}]},"item_4_text_4":{"attribute_name":"著者所属","attribute_value_mlt":[{"subitem_text_value":"地震研究所"}]},"item_creator":{"attribute_name":"著者","attribute_type":"creator","attribute_value_mlt":[{"creatorNames":[{"creatorName":"表, 俊一郎"}],"nameIdentifiers":[{"nameIdentifier":"133415","nameIdentifierScheme":"WEKO"}]}]},"item_files":{"attribute_name":"ファイル情報","attribute_type":"file","attribute_value_mlt":[{"accessrole":"open_date","date":[{"dateType":"Available","dateValue":"2017-06-27"}],"displaytype":"detail","filename":"ji0231004.pdf","filesize":[{"value":"2.1 MB"}],"format":"application/pdf","licensetype":"license_note","mimetype":"application/pdf","url":{"label":"ji0231004.pdf","url":"https://repository.dl.itc.u-tokyo.ac.jp/record/34315/files/ji0231004.pdf"},"version_id":"0f642ef2-7675-4350-ab6c-95bb7972af77"}]},"item_language":{"attribute_name":"言語","attribute_value_mlt":[{"subitem_language":"jpn"}]},"item_resource_type":{"attribute_name":"資源タイプ","attribute_value_mlt":[{"resourcetype":"departmental bulletin paper","resourceuri":"http://purl.org/coar/resource_type/c_6501"}]},"item_title":"4. 地震動の尾部について(其の3)","item_titles":{"attribute_name":"タイトル","attribute_value_mlt":[{"subitem_title":"4. 地震動の尾部について(其の3)","subitem_title_language":"ja"}]},"item_type_id":"4","owner":"1","path":["5120","5122"],"pubdate":{"attribute_name":"PubDate","attribute_value":"2008-06-06"},"publish_date":"2008-06-06","publish_status":"0","recid":"34315","relation_version_is_last":true,"title":["4. 地震動の尾部について(其の3)"],"weko_creator_id":"1","weko_shared_id":-1},"updated":"2022-12-19T04:09:22.080545+00:00"}