OBSERVATION OF THE TSUNAMI RUNUP IN THE HOKKAIDO TOKACHI-RIVER DUE TO THE 2011 OFF THE PACIFIC COAST OF TOHOKU EARTHQUAKE

Abstract

The 2011 Tohoku earthquake triggered a series of devastating tsunamis mainly along the Pacific coast of Japan. The tsunami waves also attacked coastlines of Hokkaido Island, and were propagated to upstream in the Tokachi River. We caught the tsunamis by our video cameras from 2 places between 16:00 and 17:50 on March 11. Based on the recorded images, movies and water levels at some gauge stations, the celerity of tsunami waves was estimated between 4.1 and 5.8 m/s. The maximum wave height was observed around 22:08 (seventh wave). Finally, characteristics of the tsunami waves were also discussed in comparison with the cases of the 2006 Kuril Islands earthquake. Our results would provide physical characteristics of tsunami waves in rivers to prevent future disasters.