The 2011 off the Pacific coast of Tohoku-oki earthquake triggered an extremely large tsunami. The authors conducted a field survey in Asahi City, Chiba Prefecture, after the occurrence of the earthquake. Although located farther away from the source region of the earthquake, there was still significant damage in this area. Tsunami-inundated areas in Asahi City were identified from the map developed by disaster relief volunteers and the satellite images captured after the event. Polygons to demonstrate the tsunami-inundated areas were developed in the geographic information system. The authors compared the identified affected areas with the existing tsunami hazard map of Asahi City. The relationship between the tsunami-inundated areas and the locations of seawalls and tide-prevention forests was evaluated. In addition, a numerical simulation of tsunami propagation was performed and the ratio of totally collapsed buildings to the total number of buildings, that is, damage ratio, in terms of the estimated inundation depths was evaluated.
Locality on Tsunami Propagation along the Pacific Coast of the Japan Islands
