1. Department of Geology, Faculty of Science, Chulalongkorn University, Phayathai Road, Phatumwan, Bangkok 10330, Thailand
2. US Geological Survey at Department of Earth and Space Sciences, University of Washington, Seattle, Washington 98195-1310, USA
3. Geological Survey of Japan, National Institute of Advanced Industrial Science and Technology, Site C7 1-1-1 Higashi, Tsukuba 305-8567, Japan
4. Department of Earth and Space Sciences, University of Washington, Box 351310, Seattle, Washington 98195-1310, USA
5. Geoscience Australia, GPO Box 378, Canberra, Australian Capital Territory 2601, Australia

Correspondence to: Kruawun Jankaew¹ Correspondence and requests for materials should be addressed to K.J. (Email: kjankaew@yahoo.co.uk).

Abstract

Recent centuries provide no precedent for the 2004 Indian Ocean tsunami, either on the coasts it devastated or within its source area. The tsunami claimed nearly all of its victims on shores that had gone 200 years or more without a tsunami disaster¹. The associated earthquake of magnitude 9.2 defied a Sumatra–Andaman catalogue that contains no nineteenth-century or twentieth-century earthquake larger than magnitude 7.9 (ref. 2). The tsunami and the earthquake together resulted from a fault rupture 1,500 km long that expended centuries' worth of plate convergence^{2, 3, 4, 5}. Here, using sedimentary evidence for tsunamis⁶, we identify probable precedents for the 2004 tsunami at a grassy beach-ridge plain 125 km north of Phuket. The 2004 tsunami, running 2 km across this plain, coated the ridges and intervening swales with a sheet of sand commonly 5–20 cm thick. The peaty soils of two marshy swales preserve the remains of several earlier sand sheets less than 2,800 years old. If responsible for the youngest of these pre-2004 sand sheets, the most recent full-size predecessor to the 2004 tsunami occurred about 550–700 years ago.

1. Department of Geology, Faculty of Science, Chulalongkorn University, Phayathai Road, Phatumwan, Bangkok 10330, Thailand
2. US Geological Survey at Department of Earth and Space Sciences, University of Washington, Seattle, Washington 98195-1310, USA
3. Geological Survey of Japan, National Institute of Advanced Industrial Science and Technology, Site C7 1-1-1 Higashi, Tsukuba 305-8567, Japan
4. Department of Earth and Space Sciences, University of Washington, Box 351310, Seattle, Washington 98195-1310, USA
5. Geoscience Australia, GPO Box 378, Canberra, Australian Capital Territory 2601, Australia

Correspondence to: Kruawun Jankaew¹ Correspondence and requests for materials should be addressed to K.J. (Email: kjankaew@yahoo.co.uk).

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