虚拟震源测深法及其在INDEPTH-3台阵中的应用

Virtual deep seismic sounding method and it’s application in Tibet

基于中美合作项目INDEPTH第3期在青藏高原布设的台站,使用虚拟震源测深法研究青藏高原中部的地壳厚度。结果显示,拉萨地体和羌塘地体的地壳结构存在巨大差异。拉萨地体的地壳厚度大约为57 km,与艾里均衡说预测的地壳厚度基本一致,说明拉萨地体的地壳结构比较简单。羌塘地体的地壳厚度为60~75 km,向北有增厚趋势,明显较艾里均衡说预测的地壳厚,说明羌塘地体地壳结构比较复杂,原因有可能是羌塘地体下存在高温流体和低速带,或者与印度板块岩石圈在班公湖-怒江缝合带以北向下俯冲有关。

Based on the stations deployed by project INDEPTH-3,virtual deep seismic sounding(VDSS)method was applied to study the crustal thickness in central Tibet.The results reveal that the huge difference between the crustal structure beneath Lhasa Terrane and Qiangtang Terrane.The crustal thickness beneath Lhasa Terrane is about 57 km,which is consistent with the crustal thickness predicted by Airy isostasy,indicating that the crustal structure beneath Lhasa Terrane is relatively simple.In addition,the crustal thickness beneath Qiangtang Terrane is from 60 to 75 km and thicker than that predicated from Airy isostasy.The results suggest that the crustal structure beneath Qiangtang Terrane is complicated and the reasons are possibly thermo-fluid and low velocity zone that may exist or Indian lithosphere subducting northward from Bangong-Nujiang suture.