An efficient method to improve travel time delays of transoceanic tsunamis based on depth-correction scheme

This present study aims to reduce the systematic arrival time discrepancies between observed and modeled waveforms in the deep ocean effectively. We proposed an effective depth-correction method to mimic the secondary physical effects by deriving the effective ocean depth from the rewritten dispersion relation expressions. It follows the reduction in tsunami phase speed due to weakly Boussinesq dispersion, density stratification, and the Earth’s loading elastic effects that were matched by ocean depth reduction. In practice, the implementation of the method simply requires replacing real ocean bathymetry with effective depth without additional calculation cost and parameterization adjustments for individual prediction points. We applied this method to the 2010 Chile and 2011 Tohoku-Oki tsunamis. The results indicate that the depth-correction scheme can greatly reduce the delay discrepancies not only at selected DART stations but also over the entire computational domain with dozens of times less computing cost than direct numerical simulations by coupling secondary physical effects. The improvement of delays amounted to approximately 60 to 85% on average for the two events with combined depth-correction schemes. It also suggests that the ability of depth-correction method to predict far-field tsunamis arrival time with high accuracy has important implications for real-time tsunami warning and waveform inversion.