The 2011 Japan tsunami current velocity measurements from survivor videos at Kesennuma Bay using LiDAR

TLDR

The March 11, 2011 Tohoku earthquake (M 9.0) triggered a devastating tsunami that caused widespread damage and loss of life. The study aimed to analyze tsunami flow velocities using two survivor videos captured from rooftops in Kesennuma Bay. A terrestrial LiDAR scanner calibrated camera fields of view, rectified the video images with a direct linear transformation, and then applied cross‑correlation particle image velocimetry to derive instantaneous tsunami flow velocity fields. Measured maximum tsunami height of 9 m in the Kesennuma Bay narrows was followed by peak outflow currents of 11 m/s within less than 10 minutes.

Abstract

On March 11, 2011, a magnitude M w 9.0 earthquake occurred off the coast of Japan's Tohoku region causing catastrophic damage and loss of life. The tsunami flow velocity analysis focused on two survivor videos recorded from building rooftops at Kesennuma Bay along Japan's Sanriku coast. A terrestrial laser scanner was deployed at the locations of the tsunami eyewitness video recordings. The tsunami current velocities through the Kesennuma Bay are determined in a four step process. The LiDAR point clouds are used to calibrate the camera fields of view in real world coordinates. The motion of the camera during recordings was determined. The video images were rectified with direct linear transformation. Finally a cross‐correlation based particle image velocimetry analysis was applied to the rectified video images to determine instantaneous tsunami flow velocity fields. The measured maximum tsunami height of 9 m in the Kesennuma Bay narrows were followed by maximum tsunami outflow currents of 11 m/s less than 10 minutes later.