Coastal wave reflection, directional spread, and seismoacoustic noise sources

Coastal reflection is introduced in a phase-averaged numerical wave model, first with a constant coefficient, and then with a reflection coefficient defined from the shoreface slope and that depends on the incident wave height and mean frequency. This parameterization is used in both regular and unstructured grids. The calibration involves a site-specific shoreface slope that is associated with the local geomorphology of the shoreline. Using wave buoy data off Hawaii and the U.S. West Coast, it is found that coastal reflection is necessary to reproduce observed directional properties of coastal sea states. Errors on the mean directional spread are reduced by up to 30% for the frequency band 0.04 to 0.30 Hz with, at most locations, very little impact on the mean direction and energy levels. The most accurate results are obtained using the parameterization based on the shoreface slope, provided that this slope is estimated accurately. These parameterizations are validated using seismic noise data. Using data from the U. S. West Coast it is shown that the reflection defined from the shoreface slope can improve the correlation between measured and modeled seismic noise.