Abstract
The Obama geothermal field is located on the western part of Kyushu Island, Japan. This area has importance due to its high geothermal content which attracts sporadic researchers for study. In 2003 and 2004, Obama was covered by gravity surveys to monitor and evaluate the geothermal field. In this paper, the surveyed gravity data will be used in order to delineate and model the subsurface structure of the study area. Gradient methods such as analytic signal and vertical derivatives were applied to the gravity data. The available borehole data and the results of the gradient interpretation techniques were used to model the Obama geothermal field. In general, the obtained results show that the gradient interpretation techniques are useful to obtain geologic information from gravity data.