Monitoring of Gravity Changes Associated with Geothermal Power Production at Yanaizu-Nishiyama in Japan

Abstract

In 1997, the New Energy and Industrial Technology Development Organization (NEDO) launched a new project on Reservoir Mass and Heat Flow Characterization.As part of the project gravity monitoring was carried out to detect reservoir mass changes in the geothermal field, northeast Japan. Seasonal gravity monitoring at 138 stations, daily gravity monitoring at 9 stations and continuous gravity monitoring at one station have been done. The magnitude of gravity changes monitored 1997 to 1998 was as small as between -0.2 and Precise noise reduction is essential for detecting gravity changes due to reservoir mass changes. Several natural phenomena that might have effects on gravity changes have been considered and measurements of such phenomena have been accomplished. This paper outlines the gravity monitoring program and recent results.