Hurricanes and tsunamis are responsible for major amounts of sediment redistribution in coastal areas. Differing flow conditions during these two types of events result in different spatial and temporal sediment transport patterns, which form deposits with different features. For example, tsunamis contain few large waves (typically 10 or less) while hurricanes contain thousands of waves. This results in tsunami deposits having few layers while hurricane deposits can be composed of many layers. In addition, wave periods are much longer during tsunamis (typically tens of minutes or longer) than hurricanes (usually about 20 seconds). The longer period tsunami waves have the potential to deposit thicker individual layers because the longer flow duration can transport more sediment and a longer low flow period between waves allows more sediment to settle out of suspension. Wave periods also affect where energy is focused on irregular coastlines. The longer period tsunami waves begin refracting in deeper water and are more strongly refracted as they approach the shore. This can cause strong focusing behind headlands. We take the approach of applying simple sediment transport principles to tsunamis and hurricanes to model features of their deposits. Predictions are made for spatial and stratigraphic signatures of tsunami and hurricane deposits. Model predictions are compared to tsunami deposits from Indonesia and the West Coast of the US and hurricane deposits from Hawaii, Guam, and the East and Gulf Coasts of the US.

AAPG Search and Discovery Article #90937©1998 AAPG Annual Convention and Exhibition, Salt Lake City, Utah