Earth Planets Space, Vol. 60 (No. 8), pp. 801-808, 2008
Kristine M. Larson1 and Shin'ichi Miyazaki2
1Department of Aerospace Engineering Sciences, University of Colorado, Boulder, USA
2Department of Geophysics, Kyoto University, Kyoto, Japan
(Received May 6, 2008; Accepted June 6, 2008; Online published September 8, 2008)
The Mw 8.0 2003 Tokachi-oki earthquake offshore Hokkaido is the largest earthquake observed to date by a dense GPS network (GEONET). These GPS data are important both for resolving the geodetic signature of the earthquake itself and studies of postseismic deformation. Because GPS positions are generally estimated by averaging 24 hours of observations, it can be difficult to separate the effects of the earthquake and early postseismic deformation. In order to address this difficulty, a Kalman filtering methodology is developed that allows the estimation of the static offsets for the mainshock, its largest aftershock, and postseismic deformation in the first 24 hours. The static offsets computed for this study can be used for earthquake rupture studies while the early postseismic data can be used to evaluate frictional properties of the fault.
Key words: GPS, great earthquake, geodetic data, static offset, postseismic deformation.