Abstract
A gravity survey was carried out around Gojo City, Nara Prefecture. A total of 239 gravity stations were situated roughly 300m interval on roads. The gravity value was determined by the loop method referred to the Fundamental Station at Kyoto University by means of LaCoste and Romberg gravity meter (D-36). Two remarkable low Bouguer anomaly zones exist along the Median Tectonic Line (MTL) and the Kinokawa River. High anomaly zones are situated in the north of MTL and at the areas where the Sanbagawa metamorphic rocks with high density are exposed. Underground structure was estimated by two- and three-dimensional Talwani's method. The result shows that the Sanbagawa metamorphic rocks are sinking northwards under the Ryoke granitic rocks (which have lower density than the Sanbagawa metamorphic rocks) beyond the MTL. In the east of Gojo, the uplifted basement of Sanbagawa metamorohic rocks is estimated.
