One Year Observations with a Superconducting Gravimeter at Syowa Station, Antarctica.

概要

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Since March 22 of 1993, observations of Earth tides and Earth's free oscillations with a superconducting gravimeter (SCG) were continuing at Syowa Station, Antarctica (69.0°S, 39.5°E). Combined with the other SCG data from the global network, we expect to detect signals related with a fluid core resonance, core undertones in the fluid core, the Slichter mode of the inner core, etc. and to elucidate nature of long-period tides. Parallel observations were also continuing using a LaCoste & Romberg D gravimeter which was equipped with an electrostatic feedback amplifier and the same analog filter that were used in the SCG observations. Preliminary analyses of 1 year tidal data (March 22, 1993-March 21, 1994) generally support the previously obtained diurnal and semidiurnal tidal gravimetric factors, and confirm 10% larger M2 5 factor than the theoretical value by Dehant-Wahr. Subtraction of both short- and long-period tides from the original signals resulted in a fairly small (0.06 ugal/day: 1 μgal=10-8 m/s2) trends including instrumental drift. An rms noise level of the data obtained through the MODE filter (MODE data) is estimated typically as 5-20 ugal (1 μgal=10-11 m/s2). The recorded MODE data include high quality free oscillation signals from the Hokkaido-Nansei-Oki Earthquake (Ms =8.2) on July 12, and the earthquake of South of Mariana Island (Ms=8.2) on August 8, 1993.
日本測地学会の論文