Seismic evidence for subduction-induced mantle flows underneath Middle America
Seismic evidence for subduction-induced mantle flows underneath Middle America
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DOI：
10.1038/s41467-020-15492-6
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发表时间：
2020-04
影响因子：
16.6
通讯作者：
Hejun Zhu;R. Stern;Jidong Yang
中科院分区：
文献类型：
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作者：
Hejun Zhu;R. Stern;Jidong Yang
实验室实验和地球动力学模拟表明，极向模式和环形模式地幔流在俯冲带周围发展。在这里，我们使用通过全波形反演构建的新的 3D 方位各向异性模型来推断中美洲下方深俯冲引起的地幔流。在深度小于 150 公里的地方，极向模流垂直于中美洲海沟的轨迹。从 300 至 450 公里深度，回流围绕里维拉和大西洋板块的边缘，而逃逸流则通过巴拿马和墨西哥中部下方的板块窗口推断。此外，在 700 公里深度处，研究区域以 Farallon 异常为主，快轴垂直于其走向，表明在巨大应力的作用下形成了晶格择优取向。这些观测结果为未来地幔流模拟提供了与深度相关的地震各向异性，并呼吁进一步研究过渡带和最上层下地幔中矿物的变形机制和弹性。
Laboratory experiments and geodynamic simulations demonstrate that poloidal- and toroidal-mode mantle flows develop around subduction zones. Here, we use a new 3-D azimuthal anisotropy model constructed by full waveform inversion, to infer deep subduction-induced mantle flows underneath Middle America. At depths shallower than 150 km, poloidal-mode flow is perpendicular to the trajectory of the Middle American Trench. From 300 to 450 km depth, return flows surround the edges of the Rivera and Atlantic slabs, while escape flows are inferred through slab windows beneath Panama and central Mexico. Furthermore, at 700 km depth, the study region is dominated by the Farallon anomaly, with fast axes perpendicular to its strike, suggesting the development of lattice-preferred orientations by substantial stress. These observations provide depth-dependent seismic anisotropy for future mantle flow simulations, and call for further investigations about the deformation mechanisms and elasticity of minerals in the transition zone and uppermost lower mantle.