青藏高原东北缘基于W2度量的全波形成像

本研究收集青藏高原东北缘区域114个宽频带地震台站记录到的50个区域地震事件波形数据, 采用基于二次Wasserstein(W2)度量的全波形成像方法, 获得了10~100 s频带下该区域的高分辨率壳幔结构图像.结果显示, 秦岭造山带中下地壳呈高速特征, 表明高原内部弱物质未流入此处; 而从松潘—甘孜地块跨过昆仑断裂至秦祁地块内的中下地壳呈现低S波速、正径向各向异性(V_SH＞V_SV)和高泊松比异常, 暗示深部地壳物质存在水平流动.在秦祁地块中部, 深部地壳高速特性及负径向各向异性(V_SH＜V_SV)和低泊松比异常表明地壳流在此处已终止.此外, 龙日坝断裂在深部岩石圈表现为显著的结构异常分界线, 其可能代表了扬子块体西向楔入青藏高原的最前缘.

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 10~100 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-Garzê Block across the Kunlun Fault to the Qinling-Qilian Block presents low S-wave velocity, positive radial anisotropy (VSH > VSV), 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 (VSH < VSV) 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.