Simulation of distant tsunami propagation with a radial loading deformation effect

Abstract

A simple parameterization of the loading deformation of the seafloor is incorporated into a tsunami simulation model in order to realistically calculate tsunami travel time, especially at regions far from the source. The parameterization uses one scalar parameter that is optimized effectively by far-field, deep-sea records of recent giant tsunamis: the 2011 Tohoku and the 2010 Chilean tsunamis. Using this parameterization with the optimal values, the observed tsunamis are realistically simulated in both near and far fields. The optimal values seem equivalent for both giant tsunamis, and are relatively smaller than those previously verified for ocean tide modeling, which is reasonable because of the shorter wavelengths of tsunamis.

Numerical tsunami simulation including elastic loading and seawater density stratification

“…In agreement with previous studies [ Tsai et al , ; Watada , ; Inazu and Saito , ], our results show that the effects of loading and stratification are not negligible, at least for studies in which the precise timing and waveform of the tsunami is a concern. While the effect on near‐field tsunami waveforms (Figures a and e) is small, the arrival time discrepancies between simulations which include and do not include loading/stratification effects is 10–30 min for the far‐field tsunami waveforms in Figures b–e.…”

Traveltime delay and initial phase reversal of distant tsunamis coupled with the self‐gravitating elastic Earth

“…Inazu and Saito [] noted that traveltime delays relative to the long‐wave simulations of the two earthquakes are proportional to the tsunami traveltime and attempted to explain the delay by the static ocean loading effect in a way similar to the tide of the ocean. They adopted a traveltime correction scheme, which is mathematically equivalent to the ocean depth correction by a constant factor, to adjust the traveltime correction to the observed traveltime delay data.…”

Two subevents across the Japan Trench during the 7 December 2012 off Tohoku earthquake (Mw 7.3) inferred from offshore tsunami records

“…In general, the phase velocity of tsunamis is simply modeled by where g is the gravity acceleration and h is the sea depth. The propagation (e.g., ~0.2 km/s at a sea depth of 4 km) is 1 order of magnitude slower than that of seismic waves, and its numerical modeling accurately predicts observed travel times within only 1% error in deep seas even in far fields [e.g., Fujii and Satake , ; Inazu and Saito , ]. Analyzing tsunami records is thus suitable for locating tsunamigenic vertical seafloor displacement and is useful in constraining the results of seismograph analyses.…”