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对秦岭和华北地区地壳主要岩类１３８个样品进行高温高压实验，测量其纵波速度的结果表明，其中５４个样品出现了纵波低速现象．对出现该现象的样品的实验产物所做的肉眼和镜下观察、电子探针分析以及综合对比显示，微裂隙不是产生低速现象的决定因素，而主要是含水矿物（角闪石、黑云母等）的脱水相交和由之引发的岩石部分熔融导致岩石出现纵波低速现象．通过实验条件与中、下地壳的温度和压力等条件的类比揭示，秦岭和华北地区中、下地壳存在的低速（高导）层也可能是由含水矿物的脱水相变或岩石部分熔融引起的．
High-temperature and high-pressure experiments were carried out on 138 samples of the main crust in the Qinling and North China regions to measure their P-wave velocities. Among them, 54 samples showed a phenomenon of low P-wave velocity. Macroscopic and microscopic observations of the experimental products of the sample in which this phenomenon occurred, electron probe analysis, and a comprehensive comparisons revealed that micro-cracks are not the determinants of low-speed phenomena and are predominantly hydrous minerals (amphibole, biotite, etc.) ) And the consequent partial melting of the rock leads to a low rate of longitudinal P-wave. The analogy between the experimental conditions and the temperature and pressure of the middle and lower crust reveals that the low-velocity (high-conductivity) layer in the middle and lower crust of the Qinling and North China may also be caused by dehydration phase transition or partial melting of the rocks .