Western U.S. seismic anisotropy revealing complex mantle dynamics
Western U.S. seismic anisotropy revealing complex mantle dynamics
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DOI：
10.1016/j.epsl.2018.08.015
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发表时间：
2018-10
影响因子：
5.3
通讯作者：
Quan Zhou;Jiashun Hu;Lijun Liu;T. Chaparro;D. Stegman;M. Faccenda
中科院分区：
文献类型：
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作者：
Quan Zhou;Jiashun Hu;Lijun Liu;T. Chaparro;D. Stegman;M. Faccenda
SKS在美国西部分裂的复杂模式的起源（美国）仍然是一个持久的争论，在一个模型，同时匹配的各种SKS功能仍然缺乏。在这里，我们提出了一系列的定量地球动力学模型与数据同化，系统地评估不同的岩石圈和地幔结构对地幔流动和地震各向异性的影响。这些测试揭示了地幔变形的结构比以前想象的要复杂得多。特别是，我们发现，岩石圈厚度的变化和环形流周围的胡安德富卡板调制流量本地，但它们的共存增强了大规模的地幔变形下面的美国西部的古老的Farallon板下面的东海岸拉美国西部上地幔向东，跨越区域广泛的圆形图案SKS分裂。太平洋西北部突出的东西向各向异性模式反映了从俄勒冈州以下的板裂到斯内克河平原和黄石火山口以下，热太平洋地幔持续向东侵入大陆内部的存在。这项工作为板内火山作用的形成提供了独立的支持，该火山作用是由于侵入的浅热地幔而不是上升的地幔柱造成的。
The origin of the complex pattern of SKS splitting over the western United States (U.S.) remains a long-lasting debate, where a model that simultaneously matches the various SKS features is still lacking. Here we present a series of quantitative geodynamic models with data assimilation that systematically evaluate the influence of different lithospheric and mantle structures on mantle flow and seismic anisotropy. These tests reveal a configuration of mantle deformation more complex than ever envisioned before. In particular, we find that both lithospheric thickness variations and toroidal flows around the Juan de Fuca slab modulate flow locally, but their co-existence enhances large-scale mantle deformation below the western U.S. The ancient Farallon slab below the east coast pulls the western U.S. upper mantle eastward, spanning the regionally extensive circular pattern of SKS splitting. The prominent E–W oriented anisotropy pattern within the Pacific Northwest reflects the existence of sustaining eastward intrusion of the hot Pacific oceanic mantle to beneath the continental interior, from within slab tears below Oregon to under the Snake River Plain and the Yellowstone caldera. This work provides an independent support to the formation of intra-plate volcanism due to intruding shallow hot mantle instead of a rising mantle plume.