LAUSR

AbstractFollowing the 2010 Mentawai tsunami, observations in Sumatra by Hill et al. (J Geophys Res Solid Earth, 2012. https://doi.org/10.1029/2012jb009159) noted enhanced tsunami runup in coastal areas behind island chains. Many local communities in the region, however, falsely believed that islands provide shelter against tsunami waves. The present study aims to capture when and how island chains are amplifiers of wave energy in the coastal areas they shadow, which is often where coastal communities thrive. Physical modeling was carried out in the Directional Wave Basin at the Oregon State University O.H. Hinsdale Wave Research Laboratory. The experiment included four island configurations and three different waveforms a: solitary wave, error function wave and a leading depression N-wave. Results suggest that island chains can act as wave amplifiers, indicating potential amplification in both shoreline runup and current velocity. The amplification is, however, not consistent with every waveform. Also, in some cases, the impact of the offshore islands led to a reduction in coastal impacts. This result suggests that the offshore waveform plays an important role in the wave dynamics between the islands and on the wave uprush directly behind the islands.