HR: 08:45h
AN: G41A-04    [Abstracts]
TI: At What Exact Velocity is Earth's Center Moving?
AU: * Argus, D F
EM: Donald.F.Argus@jpl.nasa.gov
AF: Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109, United States
AB: Estimates of site velocity are determined relative to Earth's center; therefore the velocity of Earth's center is fundamental to geodesy and geoscience. I present and compare different means by which to define Earth's center. Earth's center can be defined to be either (CM) the mass center of Earth, oceans, and atmopshere, (CE) the mass center of solid Earth, or (CF) the mean position of Earth's surface. The velocity of (CM) the mass center of Earth, oceans, and atmosphere differs between ITRF2000 and ITRF2005 by nearly 2 millimeters per year, suggesting that the velocity of CM estimated using SLR is not tightly constrained. Using four space techniques I estimate the velocity of CE using two different assumptions. First, I assume that places on plate interiors are moving vertically relative to CE as predicted by a model of Earth's response to unloading of the ice sheets 10 to 20 thousand years ago. Second, I assume that places on plate interiors neither beneath nor along the margins of the former ice sheets are not moving horizontally relative to CE. The two estimates of the velocity of CE are similar and nearer the ITRF2000 estimate of the velocity of CM than the ITRF2005 estimate of the velocity of CM. My estimate of the velocity of CE is likely nearer the true velocity of CM than the estimates of the velocity of CM determined using SLR. First, no phenomenon is believed to sustain a velocity between CM and CE for many years. Second, the velocity of CE is constrained tightly by the four space techniques.
DE: 1229 Reference systems
SC: Geodesy [G]
MN: 2007 Fall Meeting