EFFECTS OF TOPOGRAPHIC OBSTACLES ON TSUNAMI PROPAGATION OVER A CONTINENTAL SHELF

At the 2011 Tohoku tsunami, the southern limit where people were victimized extended to Asahi city, Chiba Prefecture. At Iioka coast of the city, the maximum tsunamirun-up height 7.6m was recorded around 3 hours after the occurrence of the earthquake. Judging from the far propagation and long duration of the tsunami fluctuations,edge-wave mechanism could governed the event. A distinct continental shelf topography is observed in front of the coastal area which may facilitate the edge wave generation. There are, however, several protuberance geometries like capes, which may affect the edge wave propagations. Both the width and slope of the continental shelf in this site are not constant, therefore, the hypothesis that the edge wave would contribute the generation of far field disaster should be carefully examined.This study investigates the influence of the topographic obstacles on the propagation/generation of edge waves.