HR: 1400h
AN: T43B-01    [Abstracts]
TI: Sedimentary Signature of the 26 December 2004 Mega Tsunami on the Eastern Coast of Banda Aceh, Indonesia P. Wassmer, F. Lavigne, J. Sartohadi, Ph. Baumert, R. Paris
AU: * Wassmer, P C
EM: wassmerpat@aol.com
AF: LGP, University of Paris1 Sorbonne, 1, Place Aristide Briand, Meudon, 92195, France
AU: Franck, L
EM: lavigne@univ-paris1.fr
AF: LGP, University of Paris1 Sorbonne, 1, Place Aristide Briand, Meudon, 92195, France
AU: Sartohadi, J
EM: panyidiksiti@yahoo.com
AF: Fakultas Geografi , Universitas Gadjah Mada, Yogjakarta, Indonesia
AU: Baumert, P
EM: philippe_zo@yahoo.com
AF: LGP, University of Paris1 Sorbonne, 1, Place Aristide Briand, Meudon, 92195, France
AU: Paris, R
EM: raparis@univ-bpclermont.fr
AF: GEOLAB University Blaise Pascal 2, 29 Boulevard F. Mitterand, Clermont Ferrand, 63000, France
AB: The eastern part of Banda Aceh was hit by a series of waves with flow depth measured up to 15 meters. In the Kajuh district, at least seven waves were observed by eyewitnesses. They emplaced sand deposits up to 80cm in thickness. We carried out a sedimentological study of these deposits along a 2km long transect oriented according to the main run up flow direction. The sedimentary signature of the tsunami moving landward shows a succession of sequences of normally graded deposit, except for the ungraded basal layer. Close to the shoreline only one or two sequences can be observed. The number of sequences increases progressively landward to reach a maximum of seven up to 2km from the former shoreline. Further inland, the thickness of the deposits is very limited. The sequences are attributed to sediment pulses related to each new wave reaching our investigation sites. Each pulsation corresponds to the arrival of a wave front. The high turbulence led to the deposit of the coarse basal material of each sequence. At the end of each pulse the decreasing of the energy allowed deposition of the finer material. The basal layer, which is undoubtedly related to the first wave, seems to have been truncated by the second and highest wave. This explains the absence of the fine material at the top of the basal layer. Close to the shoreline, the high energy of each new wave, and probably of the backwash, may explain the small amount of sedimentary sequences.The energy decreasing 2km from the shoreline allows each wave to sign his passage, emplacing a new sequence. This sedimentary record is of high interest for its exceptional number of sequences rarely observed so far. Such recording is to be related to several factors: the succession of several high waves progressing far inland, the presence on the shore of a stock of heterometric sediments easily removable, a flat topography which reduced the turbulence of the incoming flows. However, we put in light the key role played by the micro topography on the number of sequences through a spatial analysis of the deposits based on 150 outcrops
DE: 1862 Sediment transport (4558)
DE: 3020 Littoral processes
DE: 4558 Sediment transport (1862)
DE: 4564 Tsunamis and storm surges
DE: 4863 Sedimentation (1861)
SC: Tectonophysics [T]
MN: 2007 Joint Assembly