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A 1000-yr-old tsunami in the Indian Ocean points to greater risk for East Africa

Vittorio Maselli, Davide Oppo, Andrew L. Moore, Aditya Riadi Gusman, Cassy Mtelela, David Iacopini, Marco Taviani, Elinaza Mjema, Ernest Mulaya, Melody Che, Ai Lena Tomioka, Elisante Mshiu and Joseph D. Ortiz
A 1000-yr-old tsunami in the Indian Ocean points to greater risk for East Africa
Geology (Boulder) (May 2020) Pre-Issue Publication: 808-813


The December 2004 Sumatra-Andaman tsunami prompted an unprecedented research effort to find ancient precursors and quantify the recurrence time of such a deadly natural disaster. This effort, however, has focused primarily along the northern and eastern Indian Ocean coastlines, in proximal areas hardest hit by the tsunami. No studies have been made to quantify the recurrence of tsunamis along the coastlines of the western Indian Ocean, leading to an underestimation of the tsunami risk in East Africa. Here, we document a 1000-yr-old sand layer hosting archaeological remains of an ancient coastal Swahili settlement in Tanzania. The sedimentary facies, grain-size distribution, and faunal assemblages indicate a tsunami wave as the most likely cause for the deposition of this sand layer. The tsunami in Tanzania is coeval with analogous deposits discovered at eastern Indian Ocean coastal sites. Numerical simulations of tsunami wave propagation indicate a megathrust earthquake generated by a large rupture of the Sumatra-Andaman subduction zone as the likely tsunami source. Our findings provide evidence that teletsunamis represent a serious threat to coastal societies along the western Indian Ocean, with implications for future tsunami hazard and risk assessments in East Africa.

ISSN: 0091-7613
EISSN: 1943-2682
Serial Title: Geology (Boulder)
Serial Volume: Pre-Issue Publication
Title: A 1000-yr-old tsunami in the Indian Ocean points to greater risk for East Africa
Affiliation: Dalhousie University, Department of Earth and Environmental Sciences, Halifax, NS, Canada
Pages: 808-813
Published: 20200512
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 34
Accession Number: 2020-064838
Categories: Environmental geologyGeochronology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. sects., strat. cols., sketch maps
S05°24'00" - S05°24'00", W38°58'60" - W38°58'60"
Secondary Affiliation: University of Louisiana at Lafayette, USA, United StatesEarlham College, USA, United StatesGNS Science, NZL, New ZealandUniversity of Dar es Salaam, TZA, TanzaniaUniversita di Napoli Federico II, ITA, ItalyCNR, Institute of Marine Sciences, ITA, ItalyKent State University, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2020, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 2020
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