Upper mantle deformation beneath the northeastern part of Indian plate from shear-wave splitting analysis

IF 1.4 4区 地球科学 Q3 GEOSCIENCES, MULTIDISCIPLINARY Geo-Marine Letters Pub Date : 2024-02-15 DOI:10.1007/s00367-023-00763-0
Jyotima Kanaujia, G. Surve
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Abstract

This study investigates seismic anisotropy in the northeastern region of the Indian plate, including the Eastern Himalayan front, Eastern Himalaya Syntaxis (EHS), Indo-Burmese subduction zone, Shillong Plateau, Assam foredeep, and Bengal basin. Variations in azimuthal anisotropy are interpreted in terms of pre-existing lithospheric structures, mantle flow movement, and dynamic lithospheric stresses. Analysis of shear-wave splitting (SWS) in the waveforms recorded at 64 stations yielded 305 splittings (SKS, SKKS, and PKS phases) and 386 Null measurements. Results reveal an average delay time (\(\delta \)t) of 0.95 ± 0.32 s, indicating significant anisotropy. Modeling the back-azimuthal dependence of the splitting parameters indicates two-layer anisotropy along the Eastern Himalaya, Shillong Plateau, and south of the Dauki fault contiguous with the Indo-Burmese arc. Application of the spatial coherency technique localizes the depth of the anisotropic layers in different tectonic subdivisions. Stresses and lithospheric strain associated with Absolute Plate Motion (APM) of India explain the deformation patterns gleaned from splitting measurements. A vertically coherent crust-mantle deformation is proposed at the Himalayan collision front, where east-west-oriented extensional shear stresses result in north-south compressive strains. APM-related stresses forge anisotropy in the Assam foredeep region that shows a coupled crust-mantle deformation. East-west-oriented fast polarization directions (FPDs) beneath the Shillong Plateau indicate localized mantle flow along the Dauki fault. The fast axes of anisotropy in the Indo-Burmese subduction zone align parallel to the arc. These findings enhance the knowledge of mantle dynamics in the subduction and continent-continent collision zones.

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从剪切波分裂分析印度板块东北部下方的上地幔变形
本研究调查了印度板块东北部地区的地震各向异性,包括东喜马拉雅前沿、东喜马拉雅同轴(EHS)、印缅俯冲带、新龙高原、阿萨姆邦前深海和孟加拉盆地。方位角各向异性的变化是根据原有岩石圈结构、地幔流动运动和岩石圈动态应力解释的。对 64 个站点记录的波形中的剪切波分裂(SWS)进行了分析,得出了 305 个分裂(SKS、SKS 和 PKS 阶段)和 386 个空测量值。结果显示平均延迟时间(0.95 ± 0.32 秒)为 0.95 ± 0.32 秒,表明存在明显的各向异性。对劈裂参数的后方位依赖性建模表明,沿东喜马拉雅山脉、新龙高原以及与印支-缅北弧毗连的道基断层以南存在两层各向异性。空间一致性技术的应用确定了不同构造分区中各向异性层的深度。与印度绝对板块运动(APM)相关的应力和岩石圈应变解释了从分裂测量中得出的变形模式。在喜马拉雅山碰撞前沿提出了垂直一致的地壳-地幔变形,在那里东西向的延伸剪应力导致了南北向的压缩应变。与 APM 相关的应力在阿萨姆邦前深部地区形成了各向异性,显示了地壳-地幔的耦合变形。志龙高原下东西向的快速极化方向(FPDs)表明地幔沿道基断层局部流动。印度-缅甸俯冲带的快速各向异性轴与弧平行。这些发现增进了对俯冲带和大陆-大陆碰撞带地幔动力学的了解。
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来源期刊
Geo-Marine Letters
Geo-Marine Letters 地学-地球科学综合
CiteScore
5.30
自引率
0.00%
发文量
16
审稿时长
>12 weeks
期刊介绍: Geo-Marine Letters is an international peer-reviewed journal focussing on the rapid publication of concise original studies and reviews dealing with processes, products and techniques in marine geology, geophysics, and geochemistry. Coverage spans - structural geology, including plate tectonics of recent active and passive margins - sea-bed morphology, physiography and morphodynamics - sediment transport, depositional processes and sedimentary facies analysis - stratigraphy, basin analysis and paleoenvironmental reconstruction - sea-level history, paleoproductivity, gas hydrates, salt domes and brines - sediment-water interaction and organism-sediment relationships - geochemical tracers, stable isotopes and authigenic mineral formation - geotechnical properties and application of new geo-marine techniques, and more. In addition to regular articles, reviews, discussion/reply articles and technical papers, Geo-Marine Letters welcomes contributions by guest editors in the form of conference/workshop proceedings, or bundles of papers dealing with specific themes.
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