A great earthquake with M8.0 (the 2003 Tokachi-Oki earthquake) occurred on September 26, 2003, on the plate boundary south of Hokkaido, at about the same epicenter as that of the 1952 M8.2 Tokachi-Oki earthquake. We estimated the coseismic slip-distribution using GPS data to obtain consistent results with that inferred from waveform inversions: a maximum slip larger than 5m exists around 30km NNE from the epicenter. Though the slip-deficit estimated there (80 mm/yr) by our recent study is based on a rather short period of observation (5 years) to discuss the whole seismic cycle, the maximum coseismic slip roughly accounts for the slip-deficit accumulated in the past 51 years, assuming that the back-slip rate has been nearly constant since 1952. Besides the area of the largest slip, however, an accumulated slip-deficit still remains and should be released by seismic or aseismic slip, which is now actually observed in part as postseismic slip.
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