青藏高原东北缘基于W2度量的全波形成像  

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

作　　者：董兴朋 杨顶辉[2] 蒙伟娟 DONG XingPeng;YANG DingHui;MENG WeiJuan(Institute of Geology,China Earthquake Administration,Beijing 100029,China;Department of Mathematical Sciences,Tsinghua University,Beijing 100084,China)

机构地区：[1]中国地震局地质研究所,北京100029 [2]清华大学数学科学系,北京100084

出　　处：《地球物理学报》2024年第3期843-854,共12页Chinese Journal of Geophysics

基　　金：国家自然科学基金项目(42004077,42374115)资助。

摘　　要：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.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-GarzêBlock 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.

关 键 词：青藏高原东北缘 Wasserstein度量 波形反演 地壳流 径向各向异性 泊松比 

分 类 号：P315[天文地球—地震学]