雲仙火山地域の重力異常

A Bouguer gravity anomaly map of the Unzen volcanic area founded on 590 gravity stations suggests the following volcanic structures：
1．The gravitational Unzen graben shows a linear north rim along the Chijiwa fault．However，the gravitational south rim does not coincide with the Futsu fault which is the topographical south rim of the Unzen graben．
2．The source of a low gravity anomaly in Tachibana-wan Bay has been considered as mass deficiency of caldera origin，but it may in fact be due to the emplacement of a large magma body．