The 2011 Tohoku earthquake tsunami hit wide stretch of the Pacific coast of Japan and measured tsunami inundation heights showed significant variations even along the coast line within the same bay. Lack of quantitative data of tsunami dynamics around the nearshore and inundating area makes it difficult to fully understand actual behaviors of tsunami. This study focused on the analysis of video imagery taken at Shirahama Beach in Ryori Bay, where locally concentrating tsunami inundation height was also observed. Developed analysis system enabled us to quantify the time-varying surface water fluctuations and surface water velocities. It was found through the analysis that shorter wave fluctuations excited around the nearshore breakwaters appear to have significant impacts on such locally concentrating tsunami dynamics.
