HR: 0800h
AN: V11D-0818    [Abstracts]
TI: Rapid Objective Rapid Delineation of Areas At Risk From Block-and-Ash Pyroclastic Flows
AU: Widiwijayanti, C
EM: cwidiwij@geosc.psu.edu
AF: Pennsylvania State University, 503 Deike Building, University Park, PA 16802, United States
AU: * Voight, B
EM: voight@ems.psu.edu
AF: Pennsylvania State University, 503 Deike Building, University Park, PA 16802, United States
AU: Hidayat, D
EM: Hidayat@geosc.psu.edu
AF: Pennsylvania State University, 503 Deike Building, University Park, PA 16802, United States
AU: Schilling, S
EM: voight@ems.psu.edu
AF: USGS, Cascades Volcano Observatory 1300 SE Cardinal Court, Building 10, Suite 100, Vancouver, WA 98683, United States
AB: Assessments of pyroclastic flow (PF) hazards are often based on mapping of PF and surge deposits and estimation of inundation limits, and/or computer models of varying degrees of sophistication. These methods are often limited, due to poor exposures and large uncertainties on dynamic parameters. In volcanic crises a hazard map is sorely needed, but limited time, exposures, or safety aspects may preclude field work, and insufficient time or baseline data are available for reliable dynamic simulations. We have developed a statistically constrained simulation model for PFs calibrated with data from many volcanoes to estimate potential areas of inundation from PFs, following Iverson, Schilling and Vallance (1998). The predictive equations for block-and-ash PF inundation are given by A = (0.05-0.1)V 2/3 , B = (35-40)V 2/3, where A is cross-sectional area of inundation and B is planimetric area. The proportionality coefficients were obtained from statistical analysis, and comparison of simulations to mapped deposits. The method embeds predictive equations in a GIS program coupled with DEM topography, using the LAHARZ program of Schilling (1998). Although the method is objective and reproducible, any PF hazard zone so computed should be considered as an approximate guide only, due to uncertainties on average coefficients with respect to individual PFs, DEM details, and release volumes. The gradational nested hazard maps reflect in a sense these types of uncertainty. The model does not explicitly consider dynamics aspects, which can be important. Surge impacts must be extended beyond PF hazard zones and we have explored several approaches to do this. The method has been used to quickly supply PF hazard maps in two crises, Merapi 2006, Montserrat 2006-2007. We have also compared our PFz maps (using the term coined by C. Newhall) to actual recent PF deposits, and to maps generated by several other model techniques. NSF support.
DE: 8404 Volcanoclastic deposits
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2007 Fall Meeting