HR: 0800h
AN: V31D-0645    [Abstracts]
TI: A new high-performance 3D multiphase flow code to simulate volcanic blasts and pyroclastic density currents: example from the Boxing Day event, Montserrat
AU: Ongaro, T E
EM: ongaro@pi.ingv.it
AF: Istituto Nazionale di Geofisica e Vulcanologia Centro per la Modellistica Fisica e Pericolosita' dei Processi Vulcanici, Via della Faggiola 32, Pisa, I-56126 Italy
AU: Clarke, A
EM: amanda.clarke@asu.edu
AF: Department of Geological Sciences, Arizona State University, Box 871404, Tempe, AZ 85287-1404 United States
AU: Neri, A
EM: neri@pi.ingv.it
AF: Istituto Nazionale di Geofisica e Vulcanologia Centro per la Modellistica Fisica e Pericolosita' dei Processi Vulcanici, Via della Faggiola 32, Pisa, I-56126 Italy
AU: * Voight, B
EM: voight@ems.psu.edu
AF: Geosciences, Penn State University, 334 Deike Bldg., University Park, PA 16802 United States
AU: Widiwijayanti, C
EM: cwidiwij@geosc.psu.edu
AF: Geosciences, Penn State University, 334 Deike Bldg., University Park, PA 16802 United States
AB: For the first time the dynamics of directed blasts from explosive lava-dome decompression have been investigated by means of transient, multiphase flow simulations in 2D and 3D. Multiphase flow models developed for the analysis of pyroclastic dispersal from explosive eruptions have been so far limited to 2D axisymmetric or Cartesian formulations which cannot properly account for important 3D features of the volcanic system such as complex morphology and fluid turbulence. Here we use a new parallel multiphase flow code, named PDAC (Pyroclastic Dispersal Analysis Code) (Esposti Ongaro et al., 2005), able to simulate the transient and 3D thermofluid-dynamics of pyroclastic dispersal produced by collapsing columns and volcanic blasts. The code solves the equations of the multiparticle flow model of Neri et al. (2003) on 3D domains extending up to several kilometres in 3D and includes a new description of the boundary conditions over topography which is automatically acquired from a DEM. The initial conditions are represented by a compact volume of gas and pyroclasts, with clasts of different sizes and densities, at high temperature and pressure. Different dome porosities and pressurization models were tested in 2D to assess the sensitivity of the results to the distribution of initial gas pressure, and to the total mass and energy stored in the dome, prior to 3D modeling. The simulations have used topographies appropriate for the 1997 Boxing Day directed blast on Montserrat, which eradicated the village of St. Patricks. Some simulations tested the runout of pyroclastic density currents over the ocean surface, corresponding to observations of over-water surges to several km distances at both locations. The PDAC code was used to perform 3D simulations of the explosive event on the actual volcano topography. The results highlight the strong topographic control on the propagation of the dense pyroclastic flows, the triggering of thermal instabilities, and the elutriation of finest particles, and demonstrated the formation of dense pyroclastic flows by drainage of clasts sedimented from dilute flows. Fundamental and accurate hazard information can be obtained from the simulations, and the 3D displays are readily comprehended by officials and the public, making them very effective tools for risk mitigation.
DE: 8414 Eruption mechanisms and flow emplacement
DE: 8428 Explosive volcanism
DE: 8488 Volcanic hazards and risks
SC: Volcanology, Geochemistry, Petrology [V]
MN: Fall Meeting 2005