The TsuSedMod inversion model applied to the deposits of the 2004 Sumatra and 2006 Java tsunami and implications for estimating flow parameters of palaeo-tsunami

Spiske M, Weiss R, Bahlburg H, Roskosch J, Amijaya H

Abstract

Flow depth and speed are crucial but sensitive parameters describing a tsunami's overland flow. Both parameters can be measured in post-tsunami field surveys for recent events, but are difficult to infer for ancient ones. TsuSedMod, an inverse model produced by Jaffe and Gelfenbaum (2007), can be applied to estimate both the minimum flow depth and speed by using the thickness and grain size distribution of a tsunami deposit. For given estimates of flow speeds or flow depths, the application of this code can help to evaluate the magnitude of a tsunami. In this study, we compare flow depths and flow speeds calculated with TsuSedMod to field data obtained in the aftermath of the 2004 Sumatra and 2006 Java tsunami. This study shows that the model gives a reasonable estimation of local tsunami flow depths and speeds for the analyzed tsunami runup sections. These data give information on the tsunami's onshore flow characteristics, such as the number of waves and flow deceleration due to obstacles. Sediment layers from different locations within the runup section can be correlated and assigned to the same wave. The testing of TsuSedMod on recent examples shows it to be a valuable tool for calculating flow depths and speeds of ancient tsunami. Together with the dating of respective tsunami deposits, information on magnitude and frequency of events along a particular coastline can be gained. (C) 2009 Elsevier B.V. All rights reserved.