Multi-segment earthquakes and tsunami potential of the Aleutian megathrust |
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| Authors: | Ian Shennan Ronald Bruhn George Plafker |
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| Institution: | 1. Instituto Dom Luiz and Departamento de Geologia, Faculdade de Ciências, Universidade de Lisboa, Edifício C6, Campo Grande, 1749-016 Lisboa, Portugal;2. Instituto Hidrográfico - Marinha, Rua das Trinas, 49, 1249-093 Lisboa, Portugal;3. NIOZ Royal Netherlands Institute for Sea Research, Texel, The Netherlands;4. Department of Earth Sciences, Geosciences Faculty, Utrecht University, Utrecht, The Netherlands;1. School of Biological, Earth and Environmental Sciences, UNSW Australia, Sydney, NSW 2052, Australia;2. Institute for Environmental Research, Australian Nuclear and Science Technology Organisation, Locked Bag 2001, Kirrawee DC, NSW 2232, Australia;3. Escuela de Ciencias del Mar, Pontificia Universidad Católica de Valparaíso, Casilla (P.O. Box) 1020, Valparaíso 1, Chile |
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| Abstract: | Large to great earthquakes and related tsunamis generated on the Aleutian megathrust produce major hazards for both the area of rupture and heavily populated coastlines around much of the Pacific Ocean. Here we use paleoseismic records preserved in coastal sediments to investigate whether segment boundaries control the largest ruptures or whether in some seismic cycles segments combine to produce earthquakes greater than any observed since instrumented records began. Virtually the entire megathrust has ruptured since AD1900, with four different segments generating earthquakes >M8.0. The largest was the M9.2 great Alaska earthquake of March 1964 that ruptured ～800 km of the eastern segment of the megathrust. The tsunami generated caused fatalities in Alaska and along the coast as far south as California. East of the 1964 zone of deformation, the Yakutat microplate experienced two >M8.0 earthquakes, separated by a week, in September 1899. For the first time, we present evidence that earthquakes ～900 and ～1500 years ago simultaneously ruptured adjacent segments of the Aleutian megathrust and the Yakutat microplate, with a combined area ～15% greater than 1964, giving an earthquake of greater magnitude and increased tsunamigenic potential. |
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