Abstract by Ryan Hilton
Identifying Tsunamis using Boulder Imbrication
Investigating stacks of imbricated boulders on coast lines throughout Indonesia indicates the work of either high energy storm wave events or tsunamis. By evaluating the current equations used to reconstruct flow velocities and wave heights from boulder size, beach inclination, travel distance and friction we determine that the boulders were emplaced by tsunamis rather than storms. Wave heights calculated for a tsunami to dislodge the boulders from offshore and move them 20 meters up the beach to an elevation of 5 meters is less than the height of observed tsunamis in other regions. Wave heights calculated for storm waves are 4 times greater than observed In the region. This difference is consistent with the lack of cyclones in the Indonesian region. We discuss the progress in the physical equations that describe boulder imbrication, specifically the revisions to Jonathan Nott's original equations. Our hope is that these findings will refine the ability to use imbricated boulder dimensions as a proxy for the size of past tsunamis so those living in coastal regions can prepare accordingly.