京都大学21世紀COEプログラム 活地球圏の変動解明 アジア・オセアニアから世界への発信

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Seminar Series of Active Geosphere #23

T. Satomura

Seminar Series of Active Geosphere #23: September 16, 2005

by Yoichi Fukuda
Graduate school of Science, Kyoto University

"Satellite Gravity Missions and Precise Gravimetry for Investigating the Active Geosphere"

The successful launch of CHAMP (CHAllenging Mini-satellite Payload) in 2001 and GRACE (Gravity Recovery And Climate Experiment) in 2002 has opened a new era of satellite gravimetry. Especially, GRACE is providing not only data for precise gravity mapping but also time series of global gravity fields coefficients. These data are precise enough to reveal the temporal variations of the gravity fields due to mass redistribution in and on the Earth, and will lead to understanding of various problems in the Earth sciences, i.e., meteorology, hydrology, oceanography, glaciology as well as the solid Earth sciences.

On the other hand, surface precise gravimetry by means of relative and absolute gravimeters (AG) provides a brand-new technique for multidisciplinary purposes. Those measurements are expected to reveal not only the gravity signals due to tectonic actives but also the changes of fluid envelope of the Earth, i.e., ocean loading, atmospheric pressure, soil moisture/land water, glacier movements, and so on.

Although spatial resolution or sensitivity is different between the satellite mission and the precise gravimetry, the fundamental idea or philosophy behind the techniques is the same. The basic idea of the both techniques is the detection of mass movement or redistribution as the results of various phenomena on and in the Earth. The satellite technique and surface precise gravimetry are complementary for each other, and both techniques should be combined to realize the idea. In this lecture, the basics of the Earth’s gravity fields, the surface gravity measurements and the satellite gravity missions will be given, and then some results of recent studies will be presented.

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