Gravity survey on the Mizuho Plateau, East Antarctica along the traverse routes to Dome-F from Syowa Station

Abstract

Several kinds of geophysical and glaciological surveys were carried out on the Mizuho Plateau from Syowa Station (69.0°S, 39.6°E) to Dome-F (77.4°S, 39.6°E) in 1992 by the inland traverse team of the 33rd Japanese Antarctic Research Expedition (JARE-33). The gravity measurements were conducted by LaCoste-Romberg gravity meter (G-515) at about 10km-intervals along the traverse routes. The start-and-end measurement point were the absolute gravity point (IAGBN) at Syowa Station. Along the upward route to Dome-F, the measurements were often interrupted by instrument fluctuation induced by the strong wind. The instrument was cooled down (possible occurrence of the tears) at least twice when the oversnow vehicle did not move and the electric supply was stopped. The gravity values along the traverse routes were determined considering the correction of drift rates and some tears. The gravity anomalies were calculated by making use of the data both of surface elevation from GPS positioning with some modification by atmospheric pressure and of the ice thickness from the radio-echo soundings. The obtained free-air gravity anomaly profiles correlate well with those of bedrock elevation. The continuous data of bedrock elevation beneath the Dome-F area, obtained by radio-echo soundings, revealed the basin-like topographic structure of the glacier beds surrounded by bedrocks at comparatively higher altitude, which is supported by free-air anomaly data.