HR: 16:00h
AN: G24A-01 INVITED     [Abstracts]
TI: The Gravitational Signature of the December 26, 2004 Sumatran Earthquake
AU: * Gross, R S
EM: Richard.Gross@jpl.nasa.gov
AF: Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109 United States
AU: Chao, B F
EM: Benjamin.F.Chao@nasa.gov
AF: NASA/Goddard Space Flight Center, Space Geodesy Laboratory, Greenbelt, MD 20771 United States
AB: Besides generating seismic waves, which eventually dissipate, an earthquake also generates a static displacement field everywhere within the Earth. This global displacement field rearranges the Earth's mass thereby causing the Earth's gravitational field to change. The size of this change depends upon the size and focal mechanism of the earthquake. The Sumatran earthquake of December 26, 2004 is the largest earthquake to have occurred since the 1960 Chilean earthquake. Using a spherical, layered Earth model, the coseismic effect of the Sumatran earthquake upon the Earth's gravitational field is computed to spherical harmonic degree and order 100. Modeling the earthquake as consisting of 5 subevents having a total moment magnitude M_w of 9.3, it is found that the Earth's oblateness J₂ should have decreased by 2.37×10^-11 and the Earth's pear-shapedness J₃ should have decreased by 0.63×10^-11. The predicted change in oblateness is perhaps detectable if other effects, such as those of the atmosphere, oceans, and continental water storage, can be adequately removed from the observations. The predicted change at higher degrees is compared to GRACE measurements acquired before and after the earthquake from which atmospheric and oceanic effects have been removed.
DE: 1209 Tectonic deformation (6924)
DE: 1217 Time variable gravity (7223, 7230)
DE: 1240 Satellite geodesy: results (6929, 7215, 7230, 7240)
DE: 7209 Earthquake dynamics (1242)
SC: Geodesy [G]
MN: Fall Meeting 2005