Abstract
It is thought that a considerable amount of water exists in the mantle. A presence of water in the mantle plays important roles in volcanic and seismic activities via decrease of melting temperature and weakening of rocks. Thus, determination of water content and accurate knowledge of its existence form are essential for understanding the mantle dynamics. Electrical conductivity is considered to be a physical property which is very sensitive to water. When a small amount of water exists, reduction of seismic wave velocities is several % order, whereas electrical conductivity can occasionally yield tens of magnitude difference between fluid and rock. Consequently, electrical conductivity tomography enables us to provide an opportunity to construct water distribution map in the mantle. Here I discuss on the existence form of water under the mantle condition based on the electrical conductivity measurement of the fluid-bearing rocks.
