Characteristics of Erosional Morphology Formed by Tsunami Waves along the Sanriku Coast, Northeastern Japan: Analysis Using Terrestrial Laser Scanning

This study examines the characteristics of landforms affected by the 2011 tsunami along the rocky coasts of the Sanriku area in northeastern Japan. We use terrestrial laser scanning to take detailed topographic measurements of slopes near the coast. As unique topographic characteristics, small cliffs in bedrocks frequently found near the height of the maximum tsunami surface along the coastal slopes are ascribed to cumulative erosion by repeated tsunamis in the mid to late Holocene. Shallow landslides whose scarps are located near the tsunami surface also suggest that they were triggered by water saturation and/or stripping by the tsunami flow. Such characteristic landforms require further careful analysis, not only on the Sanriku coast but also in other areas with rocky coasts, to estimate the effects of repeated tsunamis on bedrock morphology.