【摘要】 对INDEPTH-Ⅲ台站的接收函数进行扫描,利用Moho界面产生的转换波和多次波的走时信息,估计台站下方的地壳平均波速比VP/VS和地壳厚度.结果显示:(1)沿着INDEPTH-Ⅲ剖面,地壳厚度整体变化不大,均为65±5km,其中拉萨地块Moho界面埋深较羌塘地体要深约5~6km.结合其他研究资料,我们推断,在整个班公-怒江缝合带存在约10km的Moho错断,为拉萨地体北缘的地幔盖层向北俯冲到羌塘地体之下所致.(2)青藏高原地壳平均波速比整体都较高,可能与青藏高原地壳广泛存在的流体/部分熔融岩浆有关.拉萨地体北部异常高的地壳VP/VS可能与嘉黎-崩错右旋走滑断裂相关;而另一个泊松比异常区位于羌塘中北部(st36~st40),它可能是由热的地幔引起的壳内部分熔融所致.更多还原

【Abstract】 Teleseismic conversion and multiple waves recorded by the INDEPTH-Ⅲ seismic array have been used to investigate the crustal thickness and V-P/V-S ratios of the central Qinghai-Xizang Plateau.Comparison with the crustal thicknesses obtained from other studies shows good agreement,which suggests that our measurements are reliable.Our results reveal that(1) the crustal thickness is 65±5km beneath the central Tibet.On the average,the Moho in Qiangtang is 5～6km shallower than that in Lhasa terrane.(2) A～10km Moho offset occur along the BNS,which maybe result from the northward subduction of the Lhasa mantle lid beneath the Qiangtang terrane affected by the India-Asia collision.(3) Due to extensive crustal melting/fluid beneath the central Qinghai-Xizang Plateau,the average crust Poission’s ratios are high(0.25～0.32).The high Poission’s ratio abnormality in the northern Lhasa may be related to the Bong Co-Lhari fault.Another high Poission’s ratio abnormality located on the northern Qiangtang terrane(st36～st40) can be related to the crustal partial melting resulted from the high heat flux from abnormal upper-mantle beneath the north-central plateau.更多还原