Permalink : http://hdl.handle.net/2115/21503

JaLCDOI : 10.14943/gbhu.69.97

We performed gravity surveys and compiled pre-existing gravity data to obtain gravity anomalies of the Akan Caldera, eastern Hokkaido, and a new gravity map around the caldera was produced. In particular, we conducted gravity surveys on the frozen lake surface in winter to reveal a fine gravity structure. A new Bouguer anomaly map shows that the Akan Caldera is characterized by three closed mimima and takes its minimum value(～70mgal)in the central area of the caldera. It is consistent with our geologic studies suggesting that the Akan Caldera is multiple caldera. Characteristic low anomalies in the Akan Caldera gradually increase towards topographic rim outside and reach their maximum around the rims. Post-caldera volcanoes are distributed not along topographic caldera rim but along a periphery of the low-anomaly region, which is situated inside the topographic rim.