HR: 16:30h
AN: V14A-04 INVITED     [Abstracts]
TI: Numerical Simulation of Flow and Deformation in Volcanic Area
AU: * Hsieh, P
EM: pahsieh@usgs.gov
AF: U. S. Geological Survey, Mail Stop 496 345 Middlefield Road, Menlo Park, CA 94025 United States
AB: Although the uplift of land surface in volcanic terrains is commonly interpreted to result from the inflation of a magma chamber at depth, an alternative explanation is the pressurization caused by upwelling of deep hydrothermal fluids. To explore the latter mechanism, the nonisothermal, multiphase flow model TOUGH2 is used in combination with a thermo-poroelasticity model BOIT2 to simulate flow and deformation. At this preliminary stage of investigation, the two codes are not fully coupled. Instead, pressures and temperatures computed by the TOUGH2 model are imported to the BIOT2 model to compute displacements. This modeling approach is illustrated by a cylindrical subsurface domain that is 50 km in diameter and 5 km thick. The permeability and porosity are assumed to be 1 x 10^-15 m² and 0.2 respectively. Atmospheric pressure and 15 ^oC are assigned to the top surface, which represents the water table. At all other boundary surfaces, there is no flow of fluid or heat across the surface. Hydrothermal fluids are injected at a rate of 5 x 10⁵ kg (or 500 tons) per day at the center of the base of the cylindrical domain. The simulated land surface uplift after 5 years of continuous injection is of the order of 10 cm. This uplift rate is similar to those observed in volcanic areas such as Long Valley of California.
DE: 1829 Groundwater hydrology
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2005 Joint Assembly