Bouguer Gravity Anomalies in Kagoshima District, Kyushu, Japan.

Abstract

The Geological Survey of Japan, AIST is publishing gravity map series of Japan on a scale of 1:200,000. We published a new gravity map of Kagoshima district using existing 15,641 gravity points and new 236 gravity points surveyed around Amakusa Island in 2001. We estimated surficial rock density distribution using the gravity data by the ABIC minimization method. The estimated densities show geologic structures buried in pyroclastic flows and density changes can be observed in same geologic units. The Bouguer anomaly map corrected by the density distribution shows clear relations between gravity anomalies and geologic features such as the Usuki-Yatsushiro tectonic line,Kagoshima graben and calderas in the survey area.