TSUNAMI HEIGHT, OAHU, HAWAII: MODEL AND NATURE

Abstract

A 1:20,000 scale model was built of the island of Oahu and neighboring topography. The model was undistorted and rotatable so that an incoming tsunami from any direction could be easily incorporated by turning the 12' x 12' model to face the wave generator from the desired angle. The wave basin was 30' wide and 40' long; with a I-10 wave absorbing beach situated at the opposite end from the wave generator. The waves were modeled to a vertical scale of I:2000. The model was supplemented by a small-scale (1-247,500) model, also undistorted, in a transparent 6' x 12' ripple tank. This model represented the eight principal islands of the island chain and their surrounding topography. Nature data of runup height for four different tsunamis around Oahu show a strong tooal amplification effect, varying more with respect to fixed positions around the Island (prominent features, points, bays, reefs, etc.) rather than with respect to variations in deep sea direction. A less pronounced local effect was obtained in the model tests and direct point-to-point correlation of model and nature data was not very meaningful beyond a general trend agreement. The orientation effect was similar on the model as in prototype.