三维成像揭示的青藏高原地壳流体层分布

Crustal fluid layer of Qinghai-Xizang(Tibet)Plateau revealed by 3-D imaging methods

应用三维地球物理成像技术可以揭示陆域地壳的流体分布。在青藏高原,高分辨率的地震波速度三维图像是揭示高原地壳流体层分布的主要方法。从取得的三维波速、密度和电阻率图象可见,低波速、低密度和低电阻率异常指示了地壳流体层的位置和范围。同时,高波速高密度异常也揭示上方发育的屏蔽盖层。据此,划分出高原地壳的多个流体发育层的分布范围。根据地壳高分辨率地震层析成像的结果还发现,青藏高原地壳流体发育层分布,与其下面的软流圈上涌有密切关联。

Three-dimensional imaging tomography can be used for revealing the layer of containing fluid.In the Qinghai—Xizang(Tibet)Plateau,high resolution seismic tomography was carried out by using the data of the local stations and a three-dimensional image of the seismic wave velocity with a resolution of 0.5°×0.5°×10 km in the lithosphere was obtained,revealing the crust structures in and around the plateau.Combining with the density and resistivity imaging,it is found that the crustal fluid layers can be located by resulting velocity disturbance,density and resistivity images.The high velocity anomalies in the upper crust often indicate the cap layers to the fluid layers as well.Based on the images we locate several locations and their ranges of the fluid layers in the plateau.It is found that the crustal fluid layers are related spacially to the asthenosphere upwelling.