Oscillation modes of Hawaiʻi waters from the 2006 Kuril Islands tsunami

Abstract

The 2006 Kuril tsunami, while not destructive to coastal properties, resulted in prolonged oscillations in Hawai'i waters. This study reconstructs the tsunami from the seismic source parameters using a nonlinear shallow-water model and uses spectral analysis to examine the oscillation patterns and amplifications around the Hawaiian Islands. The Fast Fourier Transform of the computed sea surface elevation reveals the frequency contents of the tsunami at each grid point Contour plots of the amplitudes of the Fourier coefficients identify the energy levels and areas where strong amplification occurs. A wavelet filter extracts the free surface time histories of around the high energy periods for examination of the oscillation patterns. On a regional scale, the oscillations consist of resonance in open bays and standing waves across the island chain. Large-scale standing waves appear to be generated by the oscillations of over Penguin Bank. Around O'ahu, the time-distance diagram separates the wave traveling along the coast from the standing and progressive wave. For periods smaller than 10 minutes, the oscillation patterns are dominated by edge waves capable of traveling long distances. Energetic edge waves of longer periods are also observed. Coastal trapped waves or edge waves appear to be an efficient mechanism in transferring energy and feeding adjacent oscillation patterns.