抄録
Gravity measurements were carried out over the Yatsugatake volcanic chain as a part of multi-disciplinary research of the volcanic chain, which lies near the junction of the Median Tectonic Line and the Itoigawa-Shizuoka Tectonic Line, central Japan. Maps of Bouguer anomalies were compiled from the observed gravity data together with other available data. Except for the gravity anomalies corresponding to the Akaishi Mountain, local gravity anomalies around the Yatsugatake volcanic chain are explained by shallow density structures estimated from geological maps. The Yatsugatake volcanic chain is estimated to be on the western border of the basement high of the Kanto Mountain. A negative gravity anomaly is observed over the western flank of the volcanic chain and close to the Itoigawa-Shizuoka tectonic line. The negative gravity anomaly is explained by a low density layer caused by depression in the basement under the western flank of the volcanic chain. Locally positive gravity anomalies found over the oldest rock in the central part of the volcanic chain indicate a small scale high-density structure.
