Abstract
On March 11, 2011, a magnitude 9.0 earthquake occurred off the coast of northeast Japan. This earthquake caused a tsunami which attacked mainly Tohoku District. The 2011 Tohoku Earthquake Tsunami Joint Survey Group consisting of the members of several related academic societies was organized immediately after the disaster. From March 26, the first six 6 teams entered the Tohoku district. The present study shows the field survey results across five major bays in the south part of Iwate prefecture performed by a joint team of Yokohama National University and the University of Tokyo. The measured tsunami heights range from 7.7 m to 30.1 m. A large difference of tsunami heights was observed between in Kamaishi Bay and in Ryouishi Bay, which situation may be attributed to the presence or absence of the offshore breakwater. In Ofunato Bay, the damage is considered to be intensified due to the existence of landward low flat grounds. Further, in Ofunato Bay and Kamaishi Bay, where offshore breakwaters existed, it was assumed from the eyewitness testimony that the water flow inside the bays were comparatively small, and the speeds of the water level raise were also reduced.
