Directional Wave Spectra of Open Ocean Tsunamis: Analysis of Recent Tsunamis Based on Records from DART Buoys and Cabled Arrays off the West Coast of Canada and the USA.

We use bottom pressure records from DART buoys and the Ocean Network Canada and Ocean Observatory Initiative (USA) cabled arrays to examine directional longwave spectra for the Haida Gwaii (2012), Chilean (2014 and 2015) and Kodiak Island (2018) tsunamis in the northeast Pacific. Because of the progressive character of the tsunami waves in the open ocean, the angular wave properties of the tsunamis can be derived using techniques developed in the late 20^th century for wind-wave analyses. The angular spectra of the wave are approximated as the product of the frequency spectrum and unimodal angular distribution. Using this method, we show that typical open ocean tsunami records are separable into several temporal stages with different directional spectral properties, specifically, the leading wave stage, the reflected wave stage, and the diffusive regime . The duration and intensity of each stage depend on the region from which the tsunami originated; they are similar for the same source region but differ for different source areas.