Seismic evidence for possible entrainment of rising plumes by subducting slab induced flow in three subduction zones surrounding the Caribbean Plate

IF 2.4 3区 地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS
Morvarid Saki , Sara Aniko Wirp , Magali Billen , Christine Thomas
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Abstract

The dynamic processes associated with subducting tectonic plates and rising plumes of hot material are typically treated separately in dynamical models and seismological studies. However, various types of observations and related models indicate these processes overlap spatially. Here we use precursors to PP and SS reflecting off mantle transition zone discontinuities to map deflections of these discontinuities near three subduction zones surrounding the Caribbean Plate: 1) Lesser Antilles, 2) Middle America and 3) northern South American subduction zones. In all three regions slow seismic anomalies are present behind the sinking slab within the transition zone in tomographic images. Using array methods, we identify precursors and verify their in-plane propagation for MW ≥ 5.8 events occurring between the years 2000 and 2020 by generating a large number of source receiver combinations with reflection points in the area, including crossing ray paths. The measured time lag between PP/SS arrivals and their corresponding precursors on robust stacks are used to measure the depth of the mantle transition zone discontinuities. In all three areas we find evidence for upward deflection of the 660 discontinuity behind the sinking slab, consistent with the presence of hot plume material (average temperature anomalies of 180 to 620 K), while there is not a corresponding downward deflection of the 410 km discontinuity. One interpretation of these disparate observations is suggested based on comparison to existing models of mantle convection and subduction: plume material rising across 660 km discontinuity could be entrained by lateral flow in the transition zone induced by the nearby sinking slab, and thus delaying the rise of hot material across the 410 km discontinuity.

加勒比板块周围三个俯冲带中俯冲板诱导流可能夹带上升羽流的地震证据
在动力学模型和地震学研究中,与俯冲构造板块和上升的热物质羽流相关的动力学过程通常是分开处理的。然而,各种类型的观测和相关模型表明,这些过程在空间上是重叠的。在这里,我们利用地幔过渡带不连续面上反射的 PP 和 SS 前兆,绘制了加勒比板块周围三个俯冲带附近这些不连续面的偏转图:1)小安的列斯群岛;2)中美洲;3)南美洲北部俯冲带。在这三个地区,层析成像图中过渡带内下沉板块的后方都存在缓慢的地震异常。我们使用阵列方法,通过生成大量具有该区域反射点的震源接收器组合,包括交叉射线路径,识别前兆并验证它们在 2000 年至 2020 年期间发生的 MW ≥ 5.8 事件的平面内传播。利用测量到的 PP/SS 波到达与稳健叠加上的相应前兆波之间的时滞,来测量地幔过渡带不连续性的深度。在这三个区域,我们都发现了下沉板块后面的 660 不连续面向上偏移的证据,这与热羽流物质的存在是一致的(平均温度异常为 180 至 620 K),而 410 km 不连续面没有相应的向下偏移。根据与现有地幔对流和俯冲模型的比较,对这些不同的观测结果提出了一种解释:穿过 660 千米不连续面上升的羽状物质可能被附近下沉板块引起的过渡带横向流动所夹带,从而延迟了穿过 410 千米不连续面的热物质的上升。
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来源期刊
Physics of the Earth and Planetary Interiors
Physics of the Earth and Planetary Interiors 地学天文-地球化学与地球物理
CiteScore
5.00
自引率
4.30%
发文量
78
审稿时长
18.5 weeks
期刊介绍: Launched in 1968 to fill the need for an international journal in the field of planetary physics, geodesy and geophysics, Physics of the Earth and Planetary Interiors has now grown to become important reading matter for all geophysicists. It is the only journal to be entirely devoted to the physical and chemical processes of planetary interiors. Original research papers, review articles, short communications and book reviews are all published on a regular basis; and from time to time special issues of the journal are devoted to the publication of the proceedings of symposia and congresses which the editors feel will be of particular interest to the reader.
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