Processing and interpretation of gravity data for the Shimabara Peninsula area, southwestern Japan

Shimabara Peninsula is located in southwestern Japan. There are three geothermal areas as well as a volcano on this Peninsula. In this study, we attempt to delineate the subsurface structures of the area using integrated interpretation techniques on gravity data. This study describes data processing and interpretation methods for gravity data. This processing was required in order to estimate the depths to the gravity sources, and to estimate the locations of the contacts of density contrast. The power spectral analysis was used to delineate the regional and the local components of the Bouguer anomaly. A bandpass filter was applied in order to separate the local from the regional Bouguer anomaly. Three methods were used for estimating source depths and contact locations: the horizontal gradient method, the analytic signal method, and the Euler deconvolution method. The depth estimation resulting from the respective methods were compared, and the contact locations combined into an interpretative map showing the direction for some contacts.