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<p>The Western Sichuan region lies on the southeastern margin of the Tibetan Plateau and is a key area for understanding the eastward extrusion of plateau materials and the mechanisms of regional deformation. High-resolution imaging of crustal velocity structure and azimuthal anisotropy is essential for elucidating the seismogenic environment, earthquake-generation mechanisms, and deep geodynamic processes in this region. In this study, we use travel-time data of direct Pg and Sg phases, as well as the Pn and Sn phases, recorded by the China National Seismic Network and temporary seismic stations to conduct seismic tomography. Eikonal equation-based adjoint seismic tomography method is applied to obtain new three-dimensional, high-resolution models of P- and S-wave velocities and P-wave azimuthal anisotropy. The imaging results show that the new models are generally well correlated with the major crustal tectonic units and reveal more detailed velocity anomalies and anisotropic features. High-velocity anomalies distributed along the Longmenshan fault and the Lijiang-Xiaojinhe to Jinhe-Jinghe fault divide the study area into eastern and western parts. To the west, the crust is characterized by widespread low-velocity anomalies and high <i>V</i><sub>p</sub>/<i>V</i><sub>s</sub> ratios, supporting the crustal flow model of southeastward extrusion of Tibetan Plateau material. In contrast, the low-velocity anomalies east of the Anninghe-Zemuhe fault zone differ markedly from those in the west in terms of their origin, anisotropy, and <i>V</i><sub>p</sub>/<i>V</i><sub>s</sub> characteristics. The velocity anomaly structures and anisotropic patterns in this area are more complex, indicating differences in material transport processes. These low-velocity anomalies are likely shaped by the combined effects of deep mantle convection, eastward compression of the plateau, and material intrusion, manifested as the superposition of processes such as enrichment of weak materials, partial melting, and lateral material transport. These results provide new constraints and insights into the seismogenic mechanisms and regional tectonic deformation of the Western Sichuan region.</p>

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Three-dimensional crustal velocity structure and anisotropic features of Western Sichuan and their implications for tectonics

  • 期刊论文

  • 发表日期：

    2026年4月21日

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  • Xueyuan Huang,
  • Weitao Zhang,
  • Xijun He,
  • Yanjie Zhou,
  • Yutao Shi

摘要

The Western Sichuan region lies on the southeastern margin of the Tibetan Plateau and is a key area for understanding the eastward extrusion of plateau materials and the mechanisms of regional deformation. High-resolution imaging of crustal velocity structure and azimuthal anisotropy is essential for elucidating the seismogenic environment, earthquake-generation mechanisms, and deep geodynamic processes in this region. In this study, we use travel-time data of direct Pg and Sg phases, as well as the Pn and Sn phases, recorded by the China National Seismic Network and temporary seismic stations to conduct seismic tomography. Eikonal equation-based adjoint seismic tomography method is applied to obtain new three-dimensional, high-resolution models of P- and S-wave velocities and P-wave azimuthal anisotropy. The imaging results show that the new models are generally well correlated with the major crustal tectonic units and reveal more detailed velocity anomalies and anisotropic features. High-velocity anomalies distributed along the Longmenshan fault and the Lijiang-Xiaojinhe to Jinhe-Jinghe fault divide the study area into eastern and western parts. To the west, the crust is characterized by widespread low-velocity anomalies and high Vp/Vs ratios, supporting the crustal flow model of southeastward extrusion of Tibetan Plateau material. In contrast, the low-velocity anomalies east of the Anninghe-Zemuhe fault zone differ markedly from those in the west in terms of their origin, anisotropy, and Vp/Vs characteristics. The velocity anomaly structures and anisotropic patterns in this area are more complex, indicating differences in material transport processes. These low-velocity anomalies are likely shaped by the combined effects of deep mantle convection, eastward compression of the plateau, and material intrusion, manifested as the superposition of processes such as enrichment of weak materials, partial melting, and lateral material transport. These results provide new constraints and insights into the seismogenic mechanisms and regional tectonic deformation of the Western Sichuan region.