Tsunami arrival time characteristics of the 2011 East Japan Tsunami obtained from eyewitness accounts, evidence and numerical simulation

Abstract

Information on the tsunami arrival time for people located along a coastline is crucial for community-based tsunami preparedness activities. It is also important for tsunami source mechanism studies to support other field observation data such as run-up heights, coseismic subsidence and eyewitness accounts. In this study, we reconstructed the tsunami arrival times along the east coast of Japan during the 2011 tsunami. As most of the tide gauges were damaged, first we collected and analyzed the arrival time data from equipment that survived the tsunami. The tsunami waveforms offshore were taken from six GPS buoys covering the Fukushima coastline in the south to Aomori in the north. Next, we utilized the records from stopped clocks found in the tsunami affected areas to briefly view the inundation arrival time. In addition to the observed run-up data, we used the abovementioned arrival time information to propose and validate a new source mechanism for the 2011 Japan tsunami. The well-validated source model was then used to obtain the characteristics of the tsunami arrival time along the east coast of Japan. The results can be used as primary information for designing a community-based evacuation plan and increasing community awareness of tsunamis.