著者
弘瀬 冬樹 中島 淳一 長谷川 昭
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.60, no.3, pp.123-138, 2008-02-15 (Released:2013-08-20)
参考文献数
46
被引用文献数
5

We estimated three-dimensional seismic velocity structure in and around the Philippine Sea plate subducting beneath the Kanto district in Japan by applying the double-difference tomography method to arrival time data of earthquakes obtained by the dense nationwide seismic network (Kiban-network). A low S-wave velocity and high Vp/Vs layer with several-km thick, which is shallowly inclined toward the subducting direction of the slab, has been clearly imaged. Comparison with the location of the upper surface of the Philippine Sea slab estimated from seismic refraction surveys, hypocenter distribution of relocated earthquakes, and focal mechanisms shows that this low S-wave velocity and high Vp/Vs layer corresponds to the crust of the Philippine Sea slab. Based on the presently obtained location of the low S-wave velocity and high Vp/Vs layer, hypocenter distribution, and focal mechanisms, we estimated the configuration of the upper surface of the Philippine Sea slab in the Kanto district. Presently estimated configuration of the Philippine Sea slab shows that the slab bends concavely and the depression is located eastward compared with those of the previous studies. Most of the earthquakes associated with the Philippine Sea slab occur along the plate boundary and/ or around the slab Moho. Prominent low S-wave velocity and high Vp/Vs layer was detected at depth of 30 km beneath the region along the latitude of 35.8 degrees, suggesting the serpentinization of the forearc mantle wedge due to dehydration of subducting slab.

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弘瀬冬樹・他 "Double-Difference Tomography法による関東地方の3次元地震波速度構造およびフィリピン海プレートの形状の推定"(地震 2008) https://t.co/cZMPQboOFa
昨日の東京都23区が震源地となってた地震、弘瀬さんの論文のFig. 12をみると位置関係が分かり易い。 ちょうど低速度域と関東地震の破壊域の下限の間くらい。 弘瀬他 2008 https://t.co/agi5lbW2FF

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