Abstract:In the DD model of earthquake,it is supposed that the water come from outside of focal region. It was indicated that the high conductivity layer in middle earth's crust, which often appears in the earthquake belt and becomes the bottom of the focal region of some large earthquakes, may supply rich water for fluid diffusion[1]. But is there some interior source of water in the focal region? We take the deep physical circumstance of the focal region of the Changma earthquake in 1932,as an example to illustrate that it is possible for some earthquakes.