地震 第2輯
Online ISSN : 1883-9029
Print ISSN : 0037-1114
ISSN-L : 0037-1114
論説
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
弘瀬 冬樹中島 淳一長谷川 昭
著者情報
ジャーナル フリー

2008 年 60 巻 3 号 p. 123-138

詳細
抄録

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.

著者関連情報
© 2008 公益社団法人 日本地震学会
次の記事
feedback
Top