Tsunamis are potentially destructive events that occur due to disturbance of the sea floor, such as earthquakes or submarine landslides. Large tsunamis, such as the Japanese 2011 event, occur infrequently, so to establish long term tsunami records the sedimentary record can be used to extend the data and historic record to obtain a long term view. However, little is known about the depositional mechanisms that occur during tsunami waves. Whilst a number of tsunami deposits have been identified around the world, it is not understood how the deposit can be used to understand the wave dynamics. Here, we present a series of flume experiments to examine the depositional mechanisms of bore-type waves with differing antecedent topography. We used photogrammetry to examine the changes to the sedimentary bed pre- and post-wave train, with video used to examine sediment transport as the waves pass. A number of small cores were also examined as a proxy for what might be recovered during field-based studies. Sediment transport is primarily by near-bed or bedload transport, with lofting of sediment into the water column for larger waves. The experiments show deposition in depressions as well as in the onshore areas. The cores show no sedimentary structures that can be related to the wave forms, except for some winnowing of smaller grain sizes in erosive areas. Our results show the potential of performing flume experiments to understand tsunami dynamics which in turn will enable a greater understanding of palaeotsunami deposits.
CORE (COnnecting REpositories)
CORE (COnnecting REpositories)