Spatial heterogeneity of the mantle wedge structure and interplate coupling in the NE Japan forearc region
Spatial heterogeneity of the mantle wedge structure and interplate coupling in the NE Japan forearc region
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DOI：
10.1029/2008gl036100
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发表时间：
2008-12
影响因子：
5.2
通讯作者：
Y. Yamamoto;R. Hino;Kensuke Suzuki;Y. Ito;Tomoaki Yamada;M. Shinohara;T. Kanazawa;G. Aoki;
中科院分区：
文献类型：
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作者：
Y. Yamamoto;R. Hino;Kensuke Suzuki;Y. Ito;Tomoaki Yamada;M. Shinohara;T. Kanazawa;G. Aoki;
我们利用陆上和海上地震台站的数据，在日本东北部俯冲带的弧前区域进行了三维地震层析成像。我们以高空间分辨率获得了板块边界附近的Vp、Vs和Vp/Vs结构。重新定位的震源所确定的板块边界位置与洋壳和地幔楔之间的急速度边界重合。1978年和2005年宫城外板块间地震（M >7）同震滑区上方的地幔楔具有高Vp和Vs，但低Vp/Vs的特征。然而，在很少发生大地震的福岛附近，我们在地幔楔的尖端发现了一个高Vp/Vs异常。蛇纹岩化地幔楔的空间分布限制了板块边界强耦合区域的空间范围，从而可以解释宫城外海和福岛外海地震活动的差异。
We performed 3‐D seismic tomography in the forearc region of the northeastern Japan subduction zone using both onshore and offshore seismic station data. We obtained the Vp, Vs, and Vp/Vs structures around the plate boundary with high spatial resolution. The position of the plate boundary as defined by relocated hypocenters coincides with the sharp velocity boundary between the oceanic crust and the mantle wedge. The mantle wedge above the coseismic slip area of the 1978 and 2005 off‐Miyagi interplate earthquakes (M > 7) is characterized by high Vp and Vs, but low Vp/Vs. Off Fukushima, however, where large earthquakes rarely occur, we found a high Vp/Vs anomaly at the tip of the mantle wedge. The spatial distribution of serpentinized mantle wedge limits the spatial extent of the strongly coupled area on the plate boundary, and thus can explain the difference in seismic activity between the off‐Miyagi and off‐Fukushima regions.