COASTAL PROGRADATION IN NORTHERN SUMATRA AFTER THE 2004 SUMATRA-ANDAMAN EARTHQUAKE AND TSUNAMI

The December 2004 Sumatra-Andaman earthquake severely affected the morphology of the northern Sumatran coastline. Widespread coastal subsidence of about 1 m combined with erosion led to a complete destruction of the beach and displaced the coastline up to 300 m inland. The goal of this study is to quantify short-term coastal recovery and long-term shoreline progradation of a marshy beach ridge plain North of Meulaboh, province Aceh, an area that was severely hit by the 2004 tsunami. We carried out an auto level survey and took up to 50 sediment cores to understand the characteristic ridge and swale topography. In addition to radiocarbon dates obtained from peaty marsh deposits, we sampled a number of beach ridges for optically stimulated luminescence (OSL) dating. The obtained field data is compared to satellite images and Dutch colonial maps and yields evidence of coastal progradation over the last ~ 2000 years and the response of the coast to large subduction zone earthquakes like the one in December 2004. Preliminary results show that the coastline is prograding on average at a rate of 1-2 m per year but has grown much more rapidly at a rate of ~50 m per year since 2004.