An amalgamated meter-thick sedimentary package enabled by the 2011 Tohoku tsunami in El Garrapatero,Galapagos Islands |
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| Authors: | Maria Elizabeth Martin Arcos Breanyn Tiel MacInnes Patricia Arreaga Frances Rivera-Hernandez Robert Weiss Patrick Lynett |
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| Institution: | 1. AMEC, 2101 Webster Street, Oakland, CA 94612, USA;2. Dept. of Geological Sciences, Central Washington University, 400 E. University Way (7418), Ellensburg, WA 98926, USA;3. Instituto Oceanográfico de la Armada de Ecuador, Av. 25 de Julio-km 3 1/2 vía Pto. Marítimo Base Naval Sur, Guayaquil, Ecuador;4. Department of Earth and Space Sciences, University of Washington, Box 351310, Seattle, WA 98195-1310, USA;5. Department of Geosciences, Virginia Tech, 4044 Derring Hall (0420), Blacksburg, VA 24061, USA;6. Department of Civil and Environmental Engineering, University of Southern California, Los Angeles, CA 90089-2531, USA |
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| Abstract: | Tsunamis and storms instigate sedimentological and geomorphological changes to the coastal system, both long-term and ephemeral. To accurately predict future coastal hazards, one must identify the records that are generated by the processes associated with these hazards and recognize what will be preserved. Using eyewitness accounts, photographs, and sedimentology, this study documents pre- and post-tsunami conditions and constrains the timing and process of depositional events during and following the 11 March 2011 Tohoku tsunami in the coastal system at El Garrapatero, Galapagos Islands. While the tsunami acted as both an erosional and depositional agent, the thick, fan-like sand sheet in El Garrapatero was primarily emplaced by overwash deposition during high tide from swell waves occurring between 19–25 March and 17–22 April 2011. The swell waves were only able to access the terrestrial coastal system via a channel carved by the 2011 Tohoku tsunami through the barrier sand dune. This combined deposit could result in an overestimation of the hazard if interpreted to be the result of only one event (either tsunami or wind-generated waves). An analogous sand layer, younger than 1390–1530 cal yr BP, may record a similar, prior event. |
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| Keywords: | Tsunami deposits Coastal morphology Natural hazards |
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