Evaluating suitability of a tephra dispersal model as part of a risk assessment framework |
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| Authors: | Gordon N Keating Jon D Pelletier Greg A Valentine William Statham |
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| Institution: | 1. Earth and Environmental Sciences Division, MS D452, Los Alamos National Laboratory, Los Alamos, NM 87545 USA;2. Department of Geosciences, The University of Arizona, 1040 E. Fourth St., Tucson, AZ, 85721 USA;3. Department of Geology, 876 Natural Science Complex, University at Buffalo, Buffalo, NY 14260, USA;4. AREVA Federal Services, LLC under contract to Sandia National Laboratories, Yucca Mountain Project, 1180 North Town Center Drive, Las Vegas, NV 89144, USA |
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| Abstract: | In volcanic risk assessment it is necessary to determine the appropriate level of sophistication for a given predictive model within the contexts of multiple sources of uncertainty and coupling between models. A component of volcanic risk assessment for the proposed radioactive waste repository at Yucca Mountain (Nevada, USA) involves prediction of dispersal of contaminated tephra during violent Strombolian eruptions and the subsequent transport of that tephra toward a hypothetical individual via surface processes. We test the suitability of a simplified model for volcanic plume transport and fallout tephra deposition (ASHPLUME) coupled to a surface sediment-transport model (FAR) that calculates the redistribution of tephra, and in light of inherent uncertainties in the system. The study focuses on two simplifying assumptions in the ASHPLUME model: 1) constant eruptive column height and 2) constant wind speed and direction during an eruption. Variations in tephra dispersal resulting from unsteady column height and wind conditions produced variations up to a factor of two in the concentration of tephra in sediment transported to the control population. However, the effects of watershed geometry and terrain, which control local remobilization of tephra, overprint sensitivities to eruption parameters. Because the combination of models used here shows limited sensitivity to the actual details of ash fall, a simple fall model suffices to estimate tephra mass delivered to the hypothetical individual. |
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| Keywords: | tephra dispersal tephra redistribution risk assessment surficial processes numerical modeling uncertainty |
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