Gravity Measurements at Sea by Use of the T.S.S.G.

Abstract

Among numerous cruises on which gravity was measured by use of the T.S.S.G. the cruises of the Umitaka-maru of the Tokyo University of Fisheries made in July and August 1966 and from November 1967 to February 1968, the cruises of the Hakuho-maru of the Ocean Research Institute, University of Tokyo made in August 1967, in July and August 1968 and from April to June 1969, and the cruise of the Meiyo of the Hydrographic Office, Maritime Safety Agency of Japan are selected to illustrate actual situations of gravity measurements during each of the cruises. Gravity measurements by use of the Vening Meinesz gravity meter made in 1934 and 1935 by Matsuyama et al. are also taken up and compared with the measurements by use of the T.S.S.G.Gravity values obtained by these measurements have been compiled into gravity tables, and maps or profiles of certain tectonically intimate areas have been drawn. The areas selected from tectonical viewpoint are; Japan trench and its vicinity, Suiko sea-mount at the emperor ridge, Brisbane Hill at the coral sea, Shatzky rise (north-west Pacific rise), Bismark plateau, Mariana trench and Solomon trench.