WATER CONTENT IN THE CRUST AND THE HYDROTHERMAL REACTION AS A POSSIBLE CAUSE FOR THE SWARM-TYPE EARTHQUAKES

Abstract

The volume change by the phase transformation has been supposed as an important cause for the earthquakes. The possibility that the hydrothermal reaction will be the cause for the earthquakeswarm is studied. From the estimated curve of maximum water content in the crust, it is concluded that one of the most active region of the earthquakeswarms will be the place of active hot springs along the volcanic belt and at the depth of 3-10 km. Some estimations were attempted about Matsushiro earthquake as an example. The calculated heat energy of reaction is about 8 X 10^22 ergs and the elastic energy by the volume increase is 10^22 ergs. Enough water supply is expected on the assumptions that the vapor pressure gradient is 10^-3-10^-2 bar/cm, the clearance of crack is 10^-1-1 cm, and the porosity for crack is 10^-4-10^-5 at and around the seismic sphere.