The India–Eurasia continental collision zone (IECCZ) is an ideal setting for studying plate collision processes, plateau uplift mechanisms, and orogenic activities. Several models have attempted to explain the north–south (N‒S) collision and east–west (E‒W) extension based on geological and geophysical observations. Among them, the subduction of the subducted Indian lower crust (SILC) and the deep geometric shape of the southern Tibetan rifts are still controversial. To address these issues, we selected P- and S-wave arrival times from 35,193 earthquakes recorded by 575 permanent and temporary stations and applied an improved double-difference tomography method to obtain high-resolution 3-D P- and S-wave velocity structures of the crust and uppermost mantle and relocated earthquake event locations around the IECCZ. The N‒S velocity profiles display a northward-subducting high-velocity layer stretching from the 20–40 km depth range in the Himalayan belt to the 50–60 km depth range beneath the northern Lhasa terrane (NL), suggesting that the eclogitized SILC extended beyond the Indus–Yarlung suture, reaching the NL. Additionally, the E‒W velocity profile at the SILC front reveals a discrete high-velocity layer at depths of 40–60 km beneath the Longgar, Tingri–Nyima, Xianza-Dinggye, and Yadong–Gulu rifts, implying that the SILC experienced tearing. Based on a comprehensive analysis of the seismicity, large-earthquake source mechanisms near the Moho, and tomographic images of the study area, we proposed a new dynamic model of the India–Eurasia collision and N–S-trending rifts. The significant characteristic of this model is that the rifts cut through the crust obliquely, not vertically.

中文翻译：

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印度-欧亚大陆碰撞带周围的 3-D 高分辨率地震旅行时间断层扫描揭示了藏南高原的斜裂缝


印度-欧亚大陆碰撞带 （IECCZ） 是研究板块碰撞过程、高原隆升机制和造山活动的理想场所。一些模型试图根据地质和地球物理观测来解释南北 （N\u2012S） 碰撞和东西向 （E\u2012W） 延伸。其中，俯冲印度下地壳 （SILC） 的俯冲和藏南裂谷的深几何形状仍然存在争议。为了解决这些问题，我们从 575 个永久和临时站记录的 35,193 次地震中选择了 P 波和 S 波到达时间，并应用了改进的双差层析成像方法，以获得地壳和最上部地幔的高分辨率 3-D P 波和 S 波速度结构，并重新定位了 IECCZ 周围的地震事件位置。N\u2012S 速度剖面显示一个向北俯冲的高速层，从喜马拉雅带的 20-40 公里深度范围延伸到拉萨北部地层 （NL） 下方的 50-60 公里深度范围，表明榴辉化的 SILC 延伸到印度河-雅鲁河缝合线之外，到达 NL。此外，SILC 前沿的 E\u2012W 速度剖面揭示了 Longgar、Tingri-Nyima、Xianza-Dinggye 和 Yadong-Gulu 裂谷下方 40-60 km 深度的离散高速层，这意味着 SILC 经历了撕裂。基于对莫霍河附近地震活动、大地震源机制和研究区层析图像的综合分析，我们提出了一种新的印度-欧亚大陆碰撞和 N-S 走向裂谷的动力学模型。该模型的重要特征是裂缝是斜切的，而不是垂直的。