Anomalous low-velocity zone and linear alignment of seismicity along it in the subducted Pacific slab beneath Kanto, Japan: Reactivation of subducted fracture zone?
Anomalous low-velocity zone and linear alignment of seismicity along it in the subducted Pacific slab beneath Kanto, Japan: Reactivation of subducted fracture zone?
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DOI：
10.1029/2006gl026773
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发表时间：
2006-08-22
影响因子：
5.2
通讯作者：
Hasegawa, Akira
中科院分区：
文献类型：
--
作者：
Nakajima, Junichi;Hasegawa, Akira
[ 1]对日本关东下方震源分布的详细调查显示，俯冲太平洋板块内的地震活动呈西北-东南向线性排列。我们估计了太平洋板块的三维地震速度结构，以了解控制此类实验室内地震成因的因素。一个狭窄的低速区内的俯冲板片超过150公里的长度，部分穿透到地幔部分的板片成像。低速带在空间上与北西-南东向地震群相关。俯冲前形成的水化断裂带的复活可能与低速异常有关。水化的洋壳和洋幔的脱水反应可能会使地震速度沿着化石断裂带降低，并伴随着室内地震。这些观测结果支持脱水脆化是产生室内地震最可行机制的假设。
[ 1] A detailed investigation of the hypocenter distribution beneath Kanto, Japan, reveals a NW-SE-trending linear alignment of seismicity within the subducted Pacific slab. We estimate the 3D seismic velocity structure in the Pacific slab to understand the factors controlling the genesis of such intraslab earthquakes. A narrow low-velocity zone is imaged within the subducted slab over a length of similar to 150 km, which partly penetrates into the mantle portion of the slab. The low-velocity zone correlates in space with the NW-SE-trending earthquake cluster. A reactivation of hydrated fracture zone formed prior to subduction is probably related to the low-velocity anomaly. Dehydration reactions of the hydrated oceanic mantle as well as the oceanic crust might lower the seismic velocity along the fossil fracture zone, accompanied by intraslab earthquakes. These observations support the hypothesis of dehydration embrittlement as the most viable mechanism for generating intraslab earthquakes.