AGU - Geodesy Section

Geodesy is a branch of geophysics that studies the geometrical, structural, and gravitational properties of the Earth, their time evolution, and the dynamic interactions of the solid Earth with other physical components of the Earth system (atmosphere, hydrosphere, cryosphere, and the core), at a wide range of temporal and spatial scales. Geodesists also study the corresponding topics for other planets in the solar system.

Observations and measurements are at the heart of geodesy. Measurements of the static Earth aimed at understanding its size, shape, and motion have been made for many centuries, earning geodesy the sobriquet of "oldest Earth science." In the last half century, space techniques using extraterrestrial components and measurements have revolutionized the research and applications of geodesy, hence the term "space geodesy." Space geodetic observations are used today to measure global, regional, and local crustal deformation and gravity variability associated with a wide variety of geophysical processes; to investigate mass motions inherent in the global water cycle; to monitor atmospheric water vapor and temperature; to study the dynamics and kinematics of glaciers and ice sheets; and to study changes in the planet's moment of inertia and rotation. Due to the wide application of space geodetic observations, space geodesy has today become the most interdisciplinary branch in all of geophysics.

AGUs Geodesy Section is proud to contribute to this heritage over the decades, in providing services and fostering interactions among geodesists as well as between geodesists and colleague in other discipline

Large-scale Gravity Change Following the 2004 Sumatra-Andaman Earthquake. Image of gravity changes (microGal = 10^-8 m/s²) accumulated over 6 months after the earthquake from GRACE satellite measurements, and time series of 15-day mean gravity observations with error bars (black) and the least-square fit (thick gray). Depicted are the combination of predicted coseismic (1-day) and postseismic (viscoelastic) gravity changes from the Maxwell asthenosphere model with the viscosity of 5x10¹⁷ Pa s (yellow), 10¹⁸ Pa s (cyan), 5x10¹⁸ Pa s (blue), and 10¹⁹ Pa s (magenta) and from the bi-viscous asthenosphere model (red). (Figure adapted from Han et al. (2006), Crustal dilatation observed by GRACE after the 2004 Sumatra-Andaman earthquake, Science, 313, 658-662, and from Han et al. (2008), Implications of postseismic gravity change following the great 2004 Sumatra-Andaman earthquake from the regional harmonic analysis of GRACE intersatellite tracking data, J. Geophys. Res., 113, B11413.) (Source: Shin-Chan Han, winner of the 2009 Geodesy Section Award) Welcome to the Geodesy Section of the American Geophysical Union.


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