Gravity anomalies around Japan.

Abstract

A free-air gravity anomaly map in the vicinity of the continental shelf around Japan was compiled based on dense gravity surveys made by the Hydrographic Department of Japan (JHD). The map is presented as a supplement of the present paper. Some 92,800 gravity data contributed to the compilation of the map. A 10’× 10' block mean gravity anomaly data file was produced based on the JHDGF-T81 gravity data file which includes some 540,000 gravity sites in the western and southern Pacific areas. 10’× 10’ block mean anomalies were computed in a rectangular area bordered by the parallels N20° and N50° , and the meridians E120° and E150°. The least-squares estimation technique was adopted in computation. The block mean gravity anomalies are shown symbolically in figures. The data file of mean gravity anomalies can be used for the computation of a detailed gravimetric geoid and for other geophysical uses.