FY 1993

Comparison of T-phase spectra and tsunami amplitudes for tsunamigenic and other earthquakes

Walker, D.A., and E.N. Bernard

J. Geophys. Res., 98(C7), 12,557–12,565, doi: 10.1029/93JC00675 (1993)

T-phase spectral strengths and seismic moments from earlier studies for tsunamigenic and nontsunamigenic earthquakes off Alaska, the Aleutians, northern Honshu, and central Honshu are compared to tsunami height recordings from coastal tide gauges and deep-ocean pressure recorders. Tsunamigenic earthquakes have larger seismic moments and T-phase spectral strengths than nontsunamigenic earthquakes. Pacific-wide tsunamigenic earthquakes had well-recorded water waves on the deep-ocean pressure gauges, while water waves for the regional tsunamis could be found only on coastal tide gauges in close proximity to the earthquake epicenters. Thresholds of T-phase spectral strengths required for tsunamigenesis are estimated for each of the areas investigated. On comparing tsunami heights, seismic moments, and spectral strengths for two Pacific-wide tsunamis generated by earthquakes with similar source locations, we note that the earthquake with the larger tsunami has the larger T-phase spectral strength but smaller seismic moment. We conclude that T-phase spectral strengths may be useful in estimating tsunami energy.