Seismic anisotropy in the uppermost mantle, back‐arc region of the northeast Japan arc: Petrophysical analyses of Ichinomegata peridotite xenoliths
Seismic anisotropy in the uppermost mantle, back‐arc region of the northeast Japan arc: Petrophysical analyses of Ichinomegata peridotite xenoliths
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DOI：
10.1029/2006gl025812
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发表时间：
2006-05
影响因子：
5.2
通讯作者：
K. Michibayashi;N. Abe;A. Okamoto;T. Satsukawa;Kenta Michikura
中科院分区：
文献类型：
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作者：
K. Michibayashi;N. Abe;A. Okamoto;T. Satsukawa;Kenta Michikura
日本东北部弧区部署了密集的地震台网，以研究地幔楔结构。为了获得独立的岩石物理约束，我们确定了弧后区域的 Ichinomegata 地幔捕虏体的地震特性，这些捕虏体是通过火山喷发从地幔岩石圈带到地表的。我们根据橄榄石和辉石晶体的择优取向和单晶弹性常数计算了捕虏体的地震特性。测量到的 S 波分裂幅度较小（夹带捕虏体的区域的延迟时间为 0.22 秒）可以用大约 20 公里厚的水平各向异性层的地幔捕虏体的平均地震特性来解释，这表明地幔岩石圈可能是地震各向异性的主要来源之一；该层可能与由于沿日本东北弧的弧后扩张而导致的最上地幔岩石圈的变形有关。
A dense network of seismic stations has been deployed across the northeast Japan arc to investigate mantle wedge structures. To attain independent petrophysical constraints, we determined the seismic properties of Ichinomegata mantle xenoliths from the back‐arc region that were brought to the surface from the mantle lithosphere by volcanic eruptions. We calculated the seismic properties of the xenoliths from olivine and pyroxene crystal‐preferred orientations and single crystal elastic constants. The small magnitude of measured S‐wave splitting (delay time of 0.22 s in the area where the xenoliths were entrained) can be explained by the average seismic properties of mantle xenoliths for an approximately 20‐km thick horizontal anisotropic layer, indicating that the mantle lithosphere could be one of the dominant sources of seismic anisotropy; this layer is possibly related to deformation in the uppermost mantle lithosphere due to back‐arc spreading along the northeast Japan arc.