抄録
Residual gravity anomaly (R. G. A.) map in the northwest Pacific was made by use of sea gravity and seismic results.
R. G. A. proposed by YOSHII is powerful method to know density anomaly or tnickness anomaly of lithosphere.
R. G. A. results show that lithosphere becomes thicker towards the trench. This can be interpreted as driving force of subduction. It is difficult to determine details of it, because R. G. A. landward of the trench is not so clear.
