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建立了南北地震带北段下地壳部分熔融几何形状和分布的模型 .熔融的几何分布和连通性由以下 3个因素决定 :①熔融的位置 ;②熔融所占总体积的比例 ;③固 固和固 液界面的最小自由能 .熔融形状有薄版形、管道形和椭球包体形 .用此模型计算出含有部分熔融岩石的体积、剪切弹性模量和电导率的一般表示式 .选择参数并计算出南北地震带北段下地壳的vp、vs 和电阻率 ρs 值 ,即在鄂尔多斯地台下地壳的速度为vp ≈ 6 .71km/s,vs≈ 3.96km/s ,电阻率为上百至几百欧姆米 .而在祁连、秦岭褶皱系下地壳速度vp 约为 6 .4～ 6 .6km/s,vs 约为 3.72 ～ 3.89km/s,电阻率为几至几十欧姆米 .数值模拟的结果与地球物理反演结果基本相符 ,并进行了定性的构造解释 .用一个模型对下地壳中的速度特征与电性特性进行联合数值模拟 ,说明了此模型在解释下地壳中的vp、vs 和 ρs 的有效性 .
The model of the partial melting geometry and distribution of the lower crust of the North-South Seismic Belt has been established.The geometric distribution and connectivity of the melt are determined by the following three factors: (1) the location of the melting; (2) the proportion of the total volume of the melt; (3) The minimum free energy of the solid-liquid interface The shape of the melt is thin, tube-shaped and ellipsoid-shaped The shape, volume modulus, shear modulus of elasticity and conductivity of a partially molten rock are calculated using this model. And calculates the vp, vs and the resistivity ρs values of the lower crust in the northern segment of the North-South Seismic Belt, that is, the velocity of the crust beneath the Ordos platform is vp ≈ 6 .71km / s and vs ≈ 3.96km / s with a resistivity of hundreds To a few hundred ohm meters, while in the Qilian Qinling fold system, the vp velocity is about 6.4-6.6 km / s, vs about 3.72-3.89 km / s, and the resistivity is a few to tens of ohms meters. The results of numerical simulation are basically consistent with the results of geophysical inversion and the qualitative structural interpretation is made.Using a model to simulate the velocity and electrical characteristics of the lower crust, vp, vs and ρs .