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.

本研究调查了印度板块东北部地区的地震各向异性，包括东喜马拉雅锋、东喜马拉雅构造轴（EHS）、印缅俯冲带、西隆高原、阿萨姆邦前深部和孟加拉盆地。方位各向异性的变化可以根据预先存在的岩石圈结构、地幔流运动和动态岩石圈应力来解释。对 64 个台站记录的波形中的剪切波分裂 (SWS) 进行分析，得出 305 个分裂（SKS、SKKS 和 PKS 相位）和 386 个空测量值。结果显示平均延迟时间 ( \(\delta \) t) 为 0.95 ± 0.32 s，表明存在显着的各向异性。对分裂参数的后方位角依赖性进行建模表明，沿喜马拉雅山东部、西隆高原以及与印缅弧相邻的 Dauki 断层以南存在两层各向异性。空间相干技术的应用定位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收集到的变形模式。喜马拉雅碰撞前缘提出了垂直相干的壳幔变形，其中东西向的拉伸剪应力导致南北向的压应变。与 APM 相关的应力在阿萨姆邦前深地区形成了各向异性，显示出壳幔耦合变形。西隆高原下方东西向的快速极化方向（FPD）表明沿着道基断层的局部地幔流。印缅俯冲带各向异性的快轴与弧平行。这些发现增强了人们对俯冲带和大陆-大陆碰撞带地幔动力学的了解。