[SCG62-P04] Estimation of spatiotemporal distribution of interplate slip after the 2003 Tokachi-oki earthquake incorporating viscoelastic relaxation
Keywords:The 2003 Tokachi-oki earthquake, GNSS, Postseimsic deformation, Afterslip, Viscoelastic relaxation
For the data analysis, we corrected the effect of the 1993 Hokkaido-Nansei-oki earthquake for the observed GNSS data in Hokkaido by using the model of Ueda et al. . The secular velocity before the 2003 event was estimated from the corrected data and removed from the postseismic data. And then, we removed a seasonal variation and displacements of the M6-7 events in the postseismic period. Finally, we down-sampled the residual time series with an interval of 1-6 months. We used about 7.5 years long GNSS data until the 2011 Tohoku-oki earthquake.
For the modeling of postseismic deformation, we constructed a model consisting of the coseismic slip of the 2003 and the following M6-7 class events, interplate slip including afterslip following these events and viscoelastic relaxation. We assumed the two-layers viscoelastic structure estimated by Itoh and Nishimura  to estimate interplate slip distribution.
A preliminary result shows large postseismic slip occurred in the up-dip and down-dip extensions of the coseismic slip region and implies an interplate coupling had not been recovered to that before the 2003 event at the time of the 2011 event.