{"created":"2021-03-01T06:51:22.171277+00:00","id":32673,"links":{},"metadata":{"_buckets":{"deposit":"f7f713e8-0543-4fbc-9353-1e73da46d089"},"_deposit":{"id":"32673","owner":"1","owners":[],"pid":{"revision_id":0,"type":"depid","value":"32673"},"status":"published"},"_oai":{"id":"oai:repository.dl.itc.u-tokyo.ac.jp:00032673","sets":["80:4535:4665:4669","9:504:4538:4667:4670"]},"author_link":["126727","126726"],"item_4_alternative_title_1":{"attribute_name":"その他のタイトル","attribute_value_mlt":[{"subitem_alternative_title":"浅間火山で観測されるB型地震と爆破地震の震源メカニズムとN型地震の起源"}]},"item_4_biblio_info_7":{"attribute_name":"書誌情報","attribute_value_mlt":[{"bibliographicIssueDates":{"bibliographicIssueDate":"1990-03-15","bibliographicIssueDateType":"Issued"},"bibliographicIssueNumber":"2","bibliographicPageEnd":"265","bibliographicPageStart":"155","bibliographicVolumeNumber":"73","bibliographic_titles":[{"bibliographic_title":"東京大學地震研究所彙報 = Bulletin of the Earthquake Research Institute, University of Tokyo"}]}]},"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":"B-type, explosion and N-type earthquakes recorded by short period seismographs at Asama volcano, central Japan, are analyzed. Waveforms of B-type events are gradational from a high-frequency B-type (BH-type) to a low-frequency B-type (BL-type). Medium-frequency B-type events also exist. The focal depths of BH-type events are deeper than those of BM-type and BL-type events. The low-frequency contents (1-4 Hz) which predominate in explosion and typical BL-type events are probably Rayleigh waves. We investigated a model of body-force equivalent to explain both B-type and explosion events. Six candidates were chosen for the source model of volcanic earthquakes: 1) explosive source, 2) cylindrical model, 3) tensile crack model, 4) moment tensor Mzz component, 5) vertical single force Fz, and 6) CLVD source model. Among six candidates we found that the moment tensor Mzz component was the best fit model for the 1982 April explosion event. This implies that vibrations of the explosion event were the results of both upward and downward movement of volcanic gases. For BM-type and BL-type events, we chose a cylindrical model to explain the seismograms of these events. We conclude that waveforms of both BM-type and BL-type events are excited not only by the pressure increase, but also by the pressure decrease associated with the emission of volcanic gases.","subitem_description_type":"Abstract"},{"subitem_description":"浅間火山の火山性地震の観測は1910年にOMORI(1912)により開始された.浅間火山は桜島火山・十勝岳と同様の安山岩質の活火山であり,ブルカノ式の爆発的な噴火をする火山として知られている.1910年から1960年代のはじめにかけて,浅間火山は活発な噴火活動を繰り返した.最近では,1982年1983年に2回の噴火活動を行った後,静穏な状態が続いている.浅間火山に発生する火山性地震は,1)通常の構造性の地震に波形が似たP相・S相の比較的明瞭なA型地震,2)初動の立ち上がりも,S相も不明瞭でenvelopeが紡錘形の,安山岩質の火山に特徴的なB型地震,3)5-9Hzの比較的高周波で始まり,2-4Hzのmonochromaticな波が長時間継続し,時には振動継続時間が10分間にも及ぶことのあるN型(T型)地震,4)火山の爆発に伴って発生する爆発地震,5)火山性微動,の5種類に大別される.A型地震は浅間火山の火口の西側山体の海水面下1-4kmの範囲と火口の東側約2.6kmにある観測点SAN付近を震央とし,震源の深さが海水面付近の山体に発生する.それ以外の2)-5)の火山性地震はマグマが地表に流出する経路となる火道にその振動の起源を持つ.MINAKAMI(1960)はB型地震の日別発生頻度から,浅間火山の噴火の確率的な予測を行う事に成功した.これは,浅間火山の活動とB型地震の発生頻度との相関が極めて良く,B型地震の発生頻度がある程度増加すると,浅間火山が必ず噴火するという単純明快な観測事実に基礎を置いている.ところで,浅間火山・桜島・十勝岳のB型地震は互いに波形は良く似ている.しかし,N型地震は浅間火山と十勝岳には発生するが,桜島火山には発生しない.これはN型地震の発生が火山体の構造に依存することを意味する.本研究では,浅間火山の火道に発生の起源を持つと思われるB型地震・N型地震・爆発地震の波形解析とB型地震のうちのBM(Medium-frequency B-type)とBL(Low-frequency B-type)爆発地震についてのソース・モデルの検討を行い,以下の結論を得た.","subitem_description_type":"Abstract"}]},"item_4_full_name_3":{"attribute_name":"著者別名","attribute_value_mlt":[{"nameIdentifiers":[{"nameIdentifier":"126727","nameIdentifierScheme":"WEKO"}],"names":[{"name":"沢田, 宗久"}]}]},"item_4_identifier_registration":{"attribute_name":"ID登録","attribute_value_mlt":[{"subitem_identifier_reg_text":"10.15083/0000032673","subitem_identifier_reg_type":"JaLC"}]},"item_4_publisher_20":{"attribute_name":"出版者","attribute_value_mlt":[{"subitem_publisher":"東京大学地震研究所"}]},"item_4_source_id_10":{"attribute_name":"書誌レコードID","attribute_value_mlt":[{"subitem_source_identifier":"AN00162258","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, University of Tokyo"}]},"item_4_text_4":{"attribute_name":"著者所属","attribute_value_mlt":[{"subitem_text_value":"東京大学地震研究所"},{"subitem_text_value":"メキシコ国立防災センター"}]},"item_creator":{"attribute_name":"著者","attribute_type":"creator","attribute_value_mlt":[{"creatorNames":[{"creatorName":"Sawada, Munehisa"}],"nameIdentifiers":[{"nameIdentifier":"126726","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":"2017-06-26"}],"displaytype":"detail","filename":"ji0732001.pdf","filesize":[{"value":"6.4 MB"}],"format":"application/pdf","licensetype":"license_note","mimetype":"application/pdf","url":{"label":"ji0732001.pdf","url":"https://repository.dl.itc.u-tokyo.ac.jp/record/32673/files/ji0732001.pdf"},"version_id":"eb933aa0-e7af-4c08-8615-d688a808b541"}]},"item_language":{"attribute_name":"言語","attribute_value_mlt":[{"subitem_language":"eng"}]},"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":"The Source Mechanism of B-type and Explosion Earthquakes and the Origin of N-type Earthquakes Observed at Asama Volcano, Central Japan","item_titles":{"attribute_name":"タイトル","attribute_value_mlt":[{"subitem_title":"The Source Mechanism of B-type and Explosion Earthquakes and the Origin of N-type Earthquakes Observed at Asama Volcano, Central Japan","subitem_title_language":"en"}]},"item_type_id":"4","owner":"1","path":["4669","4670"],"pubdate":{"attribute_name":"PubDate","attribute_value":"2008-05-30"},"publish_date":"2008-05-30","publish_status":"0","recid":"32673","relation_version_is_last":true,"title":["The Source Mechanism of B-type and Explosion Earthquakes and the Origin of N-type Earthquakes Observed at Asama Volcano, Central Japan"],"weko_creator_id":"1","weko_shared_id":-1},"updated":"2022-12-19T04:08:42.227637+00:00"}