Modeling of the Runup Heights of the Hokkaido-Nansei-Oki Tsunami of 12 July 1993

The Hokkaido-Nansei-Oki earthquake (M _w 7.7) of July 12, 1993, is one of the largest tsunamigenic events in the Sea of Japan. The tsunami magnitude M₁ is determined to be 8.1 from the maximum amplitudes of the tsunami recorded on tide gauges. This value is larger than M _w by 0.4 units. It is suggested that the tsunami potential of the Nansei-Oki earthquake is large for M _w . A number of tsunami runup data are accumulated for a total range of about 1000 km along the coast, and the data are averaged to obtain the local mean heights H _n for 23 segments in intervals of about 40 km each. The geographic variation of H _n is approximately explained in terms of the empirical relationship proposed by Abe (1989, 1993). The height prediction from the available earthquake magnitudes ranges from 5.0–8.4m, which brackets the observed maximum of H _w , 7.7 m, at Okushiri Island.