The 26 December 2004 Indian Ocean Tsunami: Initial Findings from Sumatra

Tsunami Sand Deposits

The researchers surveyed beach profiles to document erosion (common near the coast) and deposition (common inland) by the tsunami. Sand eroded from beaches probably provided much of the sand that was deposited inland. The survey team dug trenches in the tsunami deposits to measure their thickness and to examine other characteristics that can shed light on how high the waves were and how fast the water was flowing. Data from the sediment deposits will not only tell scientists about the recent tsunami but also help them recognize and interpret the deposits of ancient tsunamis, which, in turn, will help them better understand an area’s tsunami history and its likely tsunami risk.

See also:

• "USGS Scientists Study Sediment Deposited by 2004 Indian Ocean Tsunami" in Sound Waves, February 2005; and
• "The 26 December 2004 Indian Ocean Tsunami: Initial Findings on Tsunami Sand Deposits, Damage, and Inundation in Sri Lanka."
   

sampling a trench to study the tsunami sand deposit [larger version]

Satellite image shows location of the topographic and sediment deposit profile at Seaside Resort Hotel, illustrated below. [larger version]

Photos were taken of cross-sectional views of tsunami deposits at the village of Lampuuk. The larger photo shows that 73 cm of sand was deposited over soil (dark material in bottom center), in beds indicating multiple pulses of sand deposition. The lowermost bed, 45 cm of sand grading upward from coarse to fine, settled from suspension in a single wave and can be used to characterize the wave's height and velocity. [larger version]

The topographic and sediment deposit profile at Seaside Resort Hotel was 410 meters long and consisted of 15 trenches. [larger version]

Subsidence