HR: 09:45h
AN: G31A-08    [Abstracts]
TI: Retrieving Earthquake Signature in GRACE Data
AU: * de Viron, O
EM: deviron@ipgp.jussieu.fr
AF: Institut de Physique du Globe and University Paris 7, Place Jussieu 4, case 89, Paris, 75005, France
AU: Panet, I
EM: panet@gsi.go.jp
AF: Geographical Survey Institute (Japan) and Institut de Physique du Globe de Paris, 1 Kitasato, Tsukuba, Ibaraki, 3050811, Japan
AU: Mikhailov, V
EM: valentin@ipgp.jussieu.fr
AF: IPE (Moscow, Russia) and Institut de Physique du Globe de Paris, 4 place Jussieu, Case 89, Paris, 75005, France
AU: Van Camp, M
EM: m.vancamp@oma.be
AF: Royal Observatory of Belgium, Avenue Circulaire, 3, Brussels, 1180, Belgium
AU: Diament, M
EM: diament@ipgp.jussieu.fr
AF: Institut de Physique du Globe and University Paris 7, Place Jussieu 4, case 89, Paris, 75005, France
AB: The GRACE mission is now orbiting the Earth for several years, monitoring the time variable gravity field. Some of the observed fluctuations are due to geodynamic causes, but they are often hidden in the complex signal, composed of hydrology, ocean, atmosphere, and geodynamics, the signal of geodynamic origin being usually the smallest. In addition, dealiasing residuals and noise make the separation of the signal from the different causes more difficult. We propose a Empirical Orthogonal Function (EOF) based method to extract the signal of physical origin, under the hypothesis that the physical signal is spatially more consistent than the noise and aliasing incomplete correction. We used synthetic earthquake geoid variations located at nearly 2000 positions at the Earth surface, based on several examples of large actual subduction events. We show that we can retrieve the gravity signal caused by vertical displacement and dilatation associated with more than 98% of the earthquakes of magnitude 9 or above (Chile [1960] and Sumatra [2004]), around 60% for magnitude 8.8 (Ecuador [1906]), 40% for magnitude 8.6 (Nias [2006]), and 33% for magnitude 8.3 (Kuril [2005]). Some events, with the right properties and location, can be detected with magnitude as low as 8. We then applied the method to the GRACE data, and showed that only the Sumatra event (2004), can be retrieved at the present data quality. Those results are in agreement with the retrieval rates mentioned here above.
DE: 1217 Time variable gravity (7223, 7230)
DE: 1218 Mass balance (0762, 1223, 1631, 1836, 1843, 3010, 3322, 4532)
DE: 1240 Satellite geodesy: results (6929, 7215, 7230, 7240)
SC: Geodesy [G]
MN: 2007 Fall Meeting