{"created":"2023-07-25T11:07:07.719952+00:00","id":10741,"links":{},"metadata":{"_buckets":{"deposit":"ce44733f-1037-49a3-a11e-95d3163ed1e0"},"_deposit":{"created_by":27,"id":"10741","owners":[27],"pid":{"revision_id":0,"type":"depid","value":"10741"},"status":"published"},"_oai":{"id":"oai:nipr.repo.nii.ac.jp:00010741","sets":[]},"author_link":["23145","23144","23146","23147"],"item_10001_biblio_info_7":{"attribute_name":"書誌情報","attribute_value_mlt":[{"bibliographicIssueDates":{"bibliographicIssueDate":"2015-03","bibliographicIssueDateType":"Issued"},"bibliographicIssueNumber":"1","bibliographicPageEnd":"79","bibliographicPageStart":"66","bibliographicVolumeNumber":"9","bibliographic_titles":[{"bibliographic_title":"Polar Science"},{"bibliographic_title":"Polar Science","bibliographic_titleLang":"en"}]}]},"item_10001_description_5":{"attribute_name":"抄録","attribute_value_mlt":[{"subitem_description":"We analyze seismic data from broadband stations located on the Antarctic and Greenland ice sheets to determine polar ice seismic velocities. P-to-S converted waves at the ice/rock interface and inside the ice sheets and their multiples (the P-receiver functions) are used to estimate in-situ P-wave velocity (Vp) and P-to-S velocity ratio (Vp/Vs) of polar ice. We find that the polar ice sheets have a two-layer structure; an upper layer of variable thickness (about 2/3 of the total thickness) with seismic velocities close to the standard ice values, and a lower layer of approximately constant thickness with standard Vp but ∼25% smaller Vs. The lower layer ceiling corresponds approximately to the −30 °C isotherm. Synthetic modeling of P-receiver functions shows that strong seismic anisotropy and low vertical S velocity are needed in the lower layer. The seismic anisotropy results from the preferred orientation of ice crystal c-axes toward the vertical. The low vertical S velocity may be due to the presence of unfrozen liquids resulting from premelting at grain joints and/or melting of chemical solutions buried in the ice. The strongly preferred ice crystal orientation fabric and the unfrozen fluids may facilitate polar ice sheet basal flow.","subitem_description_type":"Abstract"}]},"item_10001_description_6":{"attribute_name":"内容記述","attribute_value_mlt":[{"subitem_description":"南極とグリーンランドの氷床に設置した広帯域地震計データにより、氷床の地震波速度を求めた。氷と岩石の境界並びに氷床内部でのPS変換波とその多重反射（P波レシーバ関数）解析により、氷床のP波速度(Vp)及びS波との比（Vp/Vs）を推定した。極域氷床は、厚さが変化しかつ平均的な氷の地震波速度を持つ「上層」（およそ全体の2/3の厚さ）、並びに厚さが一定かつ平均的なP波速度と25％小さいS波速度をもつ「下層」の、2層構造として得られた。後者は‐30°Cの等温線とほぼ対応している。P波レシーバ関数の理論波形計算により、「下層」には強い地震波異方性と低いS波速度が必要である。また氷の結晶内におけるC軸の縦方向への選択配向により異方性が形成される。低いS波速度は、氷の内部に埋没した既溶融した粒子の結合または化学抽出による不凍液の存在が原因と考えられ、氷結晶の強い選択配向と不凍液は氷床の底面滑りを助長する可能性がある。","subitem_description_type":"Other"}]},"item_10001_relation_14":{"attribute_name":"DOI","attribute_value_mlt":[{"subitem_relation_name":[{"subitem_relation_name_text":"10.1016/j.polar.2014.07.006"}],"subitem_relation_type_id":{"subitem_relation_type_id_text":"http://doi.org/10.1016/j.polar.2014.07.006","subitem_relation_type_select":"DOI"}}]},"item_access_right":{"attribute_name":"アクセス権","attribute_value_mlt":[{"subitem_access_right":"metadata only access","subitem_access_right_uri":"http://purl.org/coar/access_right/c_14cb"}]},"item_creator":{"attribute_name":"著者","attribute_type":"creator","attribute_value_mlt":[{"creatorNames":[{"creatorName":"Gérard Wittlinger"}],"nameIdentifiers":[{}]},{"creatorNames":[{"creatorName":"Véronique Farra"}],"nameIdentifiers":[{}]},{"creatorNames":[{"creatorName":"Gérard Wittlinger","creatorNameLang":"en"}],"nameIdentifiers":[{}]},{"creatorNames":[{"creatorName":"Véronique Farra","creatorNameLang":"en"}],"nameIdentifiers":[{}]}]},"item_keyword":{"attribute_name":"キーワード","attribute_value_mlt":[{"subitem_subject":"Polar ice","subitem_subject_scheme":"Other"},{"subitem_subject":"Seismic anisotropy","subitem_subject_scheme":"Other"},{"subitem_subject":"Unfrozen liquids","subitem_subject_scheme":"Other"},{"subitem_subject":"Polar ice","subitem_subject_language":"en","subitem_subject_scheme":"Other"},{"subitem_subject":"Seismic anisotropy","subitem_subject_language":"en","subitem_subject_scheme":"Other"},{"subitem_subject":"Unfrozen liquids","subitem_subject_language":"en","subitem_subject_scheme":"Other"}]},"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":"journal article","resourceuri":"http://purl.org/coar/resource_type/c_6501"}]},"item_title":"Evidence of unfrozen liquids and seismic anisotropy at the base of the polar ice sheets","item_titles":{"attribute_name":"タイトル","attribute_value_mlt":[{"subitem_title":"Evidence of unfrozen liquids and seismic anisotropy at the base of the polar ice sheets"},{"subitem_title":"Evidence of unfrozen liquids and seismic anisotropy at the base of the polar ice sheets","subitem_title_language":"en"}]},"item_type_id":"10001","owner":"27","path":["1397"],"pubdate":{"attribute_name":"公開日","attribute_value":"2015-04-02"},"publish_date":"2015-04-02","publish_status":"0","recid":"10741","relation_version_is_last":true,"title":["Evidence of unfrozen liquids and seismic anisotropy at the base of the polar ice sheets"],"weko_creator_id":"27","weko_shared_id":27},"updated":"2023-07-25T16:22:29.764413+00:00"}