Sedimentary deposits of the 26 December 2004 tsunami on the northwest coast of Aceh, Indonesia

Abstract

The 2004 Sumatra-Andaman tsunami flooded coastal northern Sumatra to a depth of over 20 m, deposited a discontinuous sheet of sand up to 80 cm thick, and left mud up to 5 km inland. In most places the sand sheet is normally graded, and in some it contains complex internal stratigraphy. Structures within the sand sheet may record the passage of up to 3 individual waves. We studied the 2004 tsunami deposits in detail along a flowparallel transect about 400 m long, 16 km southwest of Banda Aceh. Near the shore along this transect, the deposit is thin or absent. Between 50 and 400 m inland it ranges in thickness from 5 to 20 cm. The main trend in thickness is a tendency to thicken by filling low spots, most dramatically at pre-existing stream channels. Deposition generally attended inundation-along the transect, the tsunami deposited sand to within about 40 m of the inundation limit. Although the tsunami deposit contains primarily material indistinguishable from material found on the beach one month after the event, it also contains grain sizes and compositions unavailable on the current beach. Along the transect we studied, these grains become increasingly dominant both landward and upward in the deposit; possibly some landward source of sediment was exposed and exploited by the passage of the waves. The deposit also contains the unabraded shells of subtidal marine organisms, suggesting that at least part of the deposit came from offshore. Grain sizes within the deposit tend to fine upward and landward, although individual units within the deposit appear massive, or show reverse grading. Sorting becomes better landward, although the most landward sites generally become poorly sorted from the inclusion of soil clasts. These sites commonly show interlayering of sandy units and soil clast units. Deposits from the 2004 tsunami in Sumatra demonstrate the complex nature of the deposits of large tsunamis. Unlike the deposits of smaller tsunamis, internal stratigraphy is complex, and will require some effort to understand. The Sumatra deposits also show the contribution of multiple sediment sources, each of which has its own composition and grain size. Such complexity may allow more accurate modeling of flow depth and flow velocity for paleotsunamis, if an understanding of how tsunami hydraulics affect sedimentation can be established.

26 December 2004 tsunami deposits left in areas of various tsunami run up in coastal zone of Thailand

“…For instance, the thickness of the tsunami deposits, in the range of a few mm to approximately 40 cm and being approximately 10 cm on average, is very similar to those reported from the adjacent areas (Hori et al, 2007;Fujino et al, 2010), as well as from the other areas affected by the IOT (e.g., Moore et al, 2006) or other tsunamis (e.g., Gelfenbaum and Jaffe, 2003). This study found common features such as normally graded and massive layers.…”

“…During the last 15 years, much effort has been devoted to documenting the various recent tsunami deposits (Nishimura and Miyaji, 1995;Sato et al, 1995;Shi et al, 1995;Dawson et al, 1996;Minoura et al, 1997;Bourgeois et al, 1999;Gelfenbaum and Jaffe, 2003;Nanayama and Shigeno, 2006;Higman and Bourgeois, 2008;Goto et al, 2011;Moore et al, 2011). The majority of these works focused on documentation of the 2004 Indian Ocean Tsunami (IOT) depositional effects along the coasts of Sumatra (Moore et al, 2006;Razzhigaeva et al, 2006;Richmond et al, 2006;Paris et al, 2007Paris et al, , 2009, Thailand (Hori et al, 2007;Kelletat et al, 2007;Choowong et al, 2008a, b;Matsumoto et al, 2008;Sawai et al, 2009;Fujino et al, 2010;Naruse et al, 2010), Sri Lanka (Morton et al, 2008), India (Bahlburg and Weiss, 2007;Srinivasalu et al, 2007) and Maldives (Kench et al, 2006).…”

Geoarchaeological tsunami deposits at Palaikastro (Crete) and the Late Minoan IA eruption of Santorini

“…Both types of impact were recently reported in relation to the catastrophic Sumatra tsunami in December 2004 (Liu et al, 2005;Synolakis and Kong, 2006;Jaffe et al, 2006;Moore et al, 2006;Goff et al, 2006). The effects of tsunami wave action will be very much influenced by the geomorphology of the coast and the material available for deposition.…”

The 2004 Tsunami in Aceh and Southern Thailand: Coastal Ecosystem Services, Damages and Resilience

“…Moore et al (2006) provided a detailed description of sedimentary deposits along a 450 m transect south of heavily affected Lhok Nga (west of Banda Aceh): while soils were mostly scoured in the first ~50 m of impact along the transect (cf. Fig.…”