Tsunami inundation flow characteristics interpreted by survivor videos

The 2011 Tohoku earthquake tsunami totally devastated the communities of Sanriku coast. Because of the destruction of tsunami observation facilities, such as tide gauges, there are difficulties to understand local tsunami characteristics. The author analyzed the videos taken by the survivors to identify the local tsunami inundation characteristics. The video analysis in Onagawa town, Miyagi Prefecture indicates that the tsunami arrived at Onagawa town approximately 30 minutes after the earthquake occurred, and inundated up to more than 20 m in the town within 15 minutes. Also, we found that the tsunami current at the moment of wooden house destruction revealed in the video was 6.3 m/s with the flow depth of 5m. The results may contribute to understand the local tsunami flow characteristics that are not documented by the field survey and numerical models.