Distribution of inundation by the great tsunami of the 2011 M_w 9.0 earthquake off the Pacific coast of Tohoku (Japan), as revealed by ALOS imagery data

摘要

The 2011 M_w 9.0 earthquake off the Pacific coast of Tohoku (Japan) generated a great tsunami that inundated a wide area of the east coast of northeast Japan. In this study, we identify the distribution of tsunami inundation along a 340 km-long section of coast in northeast Honshu Island, based mainly on Advanced Land Observing Satellite (ALOS) imagery data and with cross-checking by aerial photographs and Google Earth images acquired before and after the 2011 earthquake. The analyses of remote-sensing imagery data, combined with fieldwork observations, show that (Ⅰ) inundation by the tsunami extended over a wide area with a large inland limit of inundation, up to ～5.5 km from the coast in low-lying areas and up to ～15 km in a narrow bay area at the mouth of a large river; and (Ⅱ) high run-ups of up to ～35 m occurred in areas with a sawtooth coastline close to the epicentre of the 2011 main shock. The results demonstrate that remote-sensing techniques provide a powerful tool for rapidly identifying the distribution of tsunami inundation caused by the 2011 great earthquake, especially in remote and rugged coastal areas, and in areas threatened by nuclear radiation leaking from the nuclear power plant at Fukushima.