tFISH/RAPiD: Rapid improvement of near-field tsunami forecasting based on offshore tsunami data by incorporating onshore GNSS data

We have developed a new algorithm that improves near-field tsunami forecasting based on offshore tsunami data soon after an earthquake by incorporating real-time onshore Global Navigation Satellite System (GNSS) data. In our algorithm, called tFISH/RAPiD (tsunami Forecasting based on Inversion for initial sea-Surface Height/Real-time Automatic detection method for Permanent Displacement), the initial sea surface height distribution estimated from rapidly acquired GNSS data provides robust finite source size information that is incorporated into an offshore tsunami data inversion for reliable tsunami predictions along the near-field coast. Our algorithm can be applicable to arbitrary types of large tsunamigenic earthquakes when the static displacements are substantial enough to be detected at onshore GNSS stations. We retrospectively applied our algorithm to the 2011 M-w 9.0 Tohoku earthquake and demonstrated its ability to provide information about disastrous tsunamis approaching wide areas along the near-field coast. Furthermore, arrival times and wave heights of large-amplitude, short-period tsunamis affecting specific near-field coasts can be predicted at least 5 min before the actual tsunami arrivals.