Anomalous deepening of a seismic belt in the upper-plane of the double seismic zone in the Pacific slab beneath the Hokkaido corner: Possible evidence for thermal shielding caused by subducted forearc crust materials
Anomalous deepening of a seismic belt in the upper-plane of the double seismic zone in the Pacific slab beneath the Hokkaido corner: Possible evidence for thermal shielding caused by subducted forearc crust materials
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DOI：
10.1016/j.epsl.2009.12.038
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发表时间：
2010-02-20
影响因子：
5.3
通讯作者：
Matsuzawa, Toru
中科院分区：
文献类型：
--
作者：
Kita, Saeko;Okada, Tomomi;Matsuzawa, Toru
太平洋板块地震的震源重新定位表明，在北海道角下80-120公里处，双地震带上平面上的地震带异常加深，而在东北和北海道东部地区，则在70-90公里处。在北海道角下进行的地震层析成像反演表明，在太平洋板块上方的地幔楔体中存在一个具有地壳物质地震速度的低速带，并与太平洋板块的上表面直接接触。这些观测表明：i)太平洋板块上方的低速带是俯冲的千岛弧前银条的一部分。2)与俯冲的、因此相对较冷的银质物质的接触阻止了地幔楔体对太平洋板块的加热，并导致北海道角以下的太平洋板块地壳的温度低于周围地区。3)榴辉岩形成相变的延迟，促进了板片地壳地震带的局部加深。(C)2009爱思唯尔B.V.保留所有权利。
Hypocenter relocations of earthquakes in the Pacific slab have shown an anomalous deepening of a seismic belt in the upper-plane of the double seismic zone at depths of 80-120 km beneath the Hokkaido corner, while it is located at depths of 70-90 km in the surrounding Tohoku and eastern Hokkaido areas. Seismic tomographic inversions performed beneath the Hokkaido corner have shown that a low-velocity zone having seismic velocities of crust materials exists in the mantle wedge just above the Pacific slab and makes direct contact with the upper surface of the Pacific slab. These observations suggest that: I) the low-velocity zone just above the Pacific slab is part of the subducted Kuril forearc sliver. 2) The contact with the subducted, and so relatively cold, sliver materials prevents the mantle wedge from heating the Pacific slab and causes a lower temperature condition in the Pacific slab crust beneath the Hokkaido corner than in the surrounding areas. 3) As a result, a delay of eclogite-forming phase transformations occurs and enhances the local deepening of the seismic belt in the slab Crust there. (C) 2009 Elsevier B.V. All rights reserved.