T-phase data and regional tsunamigenesis in Japan

Good correlations are found between T-phase spectral strengths and seismic moments for large earthquakes off the coasts of northern and central Honshu, Japan. Also, earthquakes from these areas which generated regional tsunamis in Japan have larger seismic moments and T-phase spectral strengths over the frequency range of 10 to 35 Hz than nontsunamigenic earthquakes with similar source locations. These findings are consistent with earlier observations of T phases from tsunamigenic and nontsunamigenic earthquakes near Alaska and the Aleutian Islands (Walker et al., 1992) and suggest that T-phase data may be useful in improving the reliability of tsunami warning systems.