Full-waveform tomography of the northeastern Tibetan Plateau based on the quadratic Wasserstein-metric

This study collected waveform data from 50 regional seismic events recorded by 114 broadband seismic stations located at the northeastern margin of the Tibetan Plateau. Utilizing the full-waveform inversion method based on the quadratic Wasserstein (W2) metric and operating within the 10 similar to 100 s frequency band, we obtained high-resolution crust-mantle structural images for the region. Our findings indicate that the mid-lower crust of the Qinling orogenic belt exhibits high-velocity characteristics, suggesting that the plateau' s deep crustal weak material has not infiltrated this area. However, the deep crust spanning from the Songpan-Garze Block across the Kunlun Fault to the Qinling-Qilian Block presents low S-wave velocity, positive radial anisotropy (V-sH >V-sv), and an anomalous high Poisson's ratio, hinting at the horizontal flow of deep crustal materials. In contrast, the central part of the Qinling-Qilian Block exhibits deep crustal high-velocity features accompanied by negative radial anisotropy (V-sH<V-sv) and a low Poisson's ratio anomaly, implying a cessation of crustal flow in this location. Furthermore, the Longriba Fault presents as a distinct structural anomaly boundary within the deep lithosphere, suggesting it might delineate the leading edge where the Yangtze Block is wedging westward into the Tibetan Plateau.