Accurate detection of trace amounts of water in the mantle is the key to understanding mantle evolution and dynamics, as the presence of trace amounts of water in the mantle significantly reduces the viscosity and solidus temperature of rocks. In this study, the effects of trace amounts of water incorporated into olivine, which is the main mineral of the upper mantle, on the physical characteristics of the upper mantle were determined as functions of the elastic constant, attenuation factor (Q value), and electrical conductivity as a function of water content. It was found that the lack of frequency dependence attenuation observed under the old oceanic floor at the lithosphere-asthenosphere boundary can be explained by the presence of a trace amount of water of about 200 ppm by weight only in the asthenosphere.