HR: 1340h
AN: G13A-0905    [Abstracts]
TI: Postseismic self-healing of geoid undulations by water after the 2004 Sumatra-Andaman earthquake observed with GRACE
AU: * Ogawa, R
EM: ryo@mail.sci.hokudai.ac.jp
AF: Dept. Natural History Sci., Hokkaido Univ., N10 W8 Kita-ku, Sapporo, 060-0810, Japan
AU: Heki, K
EM: heki@mail.sci.hokudai.ac.jp
AF: Dept. Natural History Sci., Hokkaido Univ., N10 W8 Kita-ku, Sapporo, 060-0810, Japan
AB: Earthquakes are accompanied with mass redistributions and cause changes in gravity field and shape of geoid, an equipotential surface coincident with the mean sea surface. Such coseismic changes were detected by satellite gravimetry after the 2004 Sumatra-Andaman Earthquake, but little has been known on what happens on geoid after the earthquake. Here we report slow postseismic recovery of coseismic geoid depression from satellite measurements. This cannot be explained with simple afterslip or viscous relaxation of Maxwellian upper mantle. It suggests the relaxation of coseismic dilatation and compression by the diffusion of supercritical H₂O abundant in the upper mantle. Such a self-healing system of coseismic geoid undulations, a brand- new role of water in mantle, would significantly reduce the amount of permanent shifts of the Earth's rotation axis by earthquakes.
DE: 1207 Transient deformation (6924, 7230, 7240)
DE: 1217 Time variable gravity (7223, 7230)
DE: 1240 Satellite geodesy: results (6929, 7215, 7230, 7240)
DE: 1829 Groundwater hydrology
DE: 3060 Subduction zone processes (1031, 3613, 8170, 8413)
SC: Geodesy [G]
MN: 2007 Fall Meeting