ADCP observations of edge waves off Oahu in the wake of the November 2006 Kuril Islands tsunami

Abstract

During the 2006 Kuril Islands tsunami, edge waves propagating along Oahu's south shore were observed via depth‐averaged ADCP velocity and pressure data acquired in real‐time by a coastal observatory at 12 m depth and 400 m offshore. Time‐varying rotary‐component velocity spectra obtained via wavelet analysis agree with the phase lag observed between pressure and each Cartesian velocity component, in indicating the directions of rotation and travel of progressive edge waves. Furthermore, the theoretical ratios between power in the free surface elevation and in each velocity component of edge waves, agree with those observed, and a nonlinear shallow‐water model shows edge waves of various modes propagating along the shore near our observation location. Importantly, the maximum surge in sea level occurred at a time when edge waves of all constituent frequencies were superposed.