Abstract Regional triplication waveforms of five intermediate-depth events are modeled to simultaneously obtain the compressional (P) and shear (SH) wave velocity structure beneath northwestern Pacific subduction zone. Both the P- and SH-wave velocity models for three different sub-regions show a low-velocity layer (LVL) with a thickness of ∼55-80 km lying above the 410-km discontinuity with a ∼900 km lateral extent from the Japan Sea to the northeastern Asian continental margin. With the dihedral angle approaching to zero around 400 km, a minute amount of melt atop the 410-km discontinuity caused by the hydrous slab might completely wet olivine grain boundaries and result in a low seismic velocity layer in this specific subduction zone. This mechanism suggests that the 410-LVL is a low viscosity zone that would partially decouple the upper mantle from the transition zone. We infer that the widespread 410-LVL provides evidence for a water-bearing mantle transition zone beneath the western Pacific subduction zone.

中文翻译：

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西北太平洋俯冲带下方 410 公里不连续面上方普遍存在的低速层：对流变学和地球动力学的影响

摘要 通过模拟五个中深事件的区域三次波形，同时获得西北太平洋俯冲带下方的纵波（P）和横波（SH）波速度结构。三个不同子区域的 P 波和 SH 波速度模型都显示了一个厚度约 55-80 公里的低速层 (LVL)，位于 410 公里不连续面上方，横向延伸距离约 900 公里。日本海至亚洲东北部大陆边缘。随着 400 公里左右的二面角接近零，由含水板片引起的 410 公里不连续面顶部的微量熔体可能会完全润湿橄榄石晶界，并在这个特定的俯冲带中形成低地震速度层。这种机制表明 410-LVL 是一个低粘度区，它将部分地将上地幔与过渡区分离。我们推断，广泛存在的 410-LVL 为西太平洋俯冲带下方的含水地幔过渡带提供了证据。