Development of a tsunami-tide interaction model with simulation of tsunami wave propagation to Korea coasts

Abstract

Simulation studies of historic and prognostic tsunamis have been performed with focus on tsunami-tide interaction. For that, a modeling system has been developed which is composed of a global tsunami model and a regional multi-nesting tide and tide-tsunami model covering the Northwest Pacific region. The tsunami generation point can be located at any point inside or outside of the regional model domain. Initially tide propagation is simulated on the regional domain until tidal motion becomes stable enough, specifying open boundary conditions based on NAO’s tidal prediction verification of the model results are made comparing with tidal information around the Korean coasts. In parallel with the tide model simulation, tsunami propagation is then simulated on the global domain. Superposition of tsunami and tide information at the open boundary of the regional tide-tsunami model leads to the simulation of tsunami-tide interaction on the regional domain. Two historic tsunami cases, 2010 Chilean and 2011 Tohoku tsunami, are simulated to estimate the tsunami-tide interaction by calculating the difference of tsunami only and tsunami-tide simulations. The tsunami waves propagated across the Pacific and swept around the main islands of Japan. It has been found that the gravity wave transformed traveling a long distance affected by the phase of tidal currents. The prognostic tsunami propagation caused by the Nankai earthquake was also tested. The most impact scenario on Korean coasts was selected among the scenarios proposed by Central Disaster Management Council, Japan. Calculations show that tsunami waves reach Cheju Island and the southern coast of Korea in approximately 3.5 and 4 hours, respectively. The arrival time lag of tsunami was generated by the tsunami-tide interaction. Also smaller wave height of the first tsunami wave was calculated depending local tidal and current conditions.