Earth crust,earth mantle and the core are three layers of earth. The average radius of the earth is about 6370 kilometers. The crust thickness is about 35 kilometers. Most destructive earthquake happened in the crust, it also occurs in asthenosphere layer. According to seismological departments’ reports, the deep focus earthquake occurs in 300-700 kilometers underground. So far, the known deepest earthquake focus is 720 kilometers. From this point of view, the traditional compression plate faulting theory could not explain the deep focus earthquake reasonably, because there are no solid matters in that deep. Scientists are trying to draw the picture of earth rocks which may help in predicting earthquake.