HR: 1340h
AN: G53B-0886    [Abstracts]
TI: Numerical models of fluid flow and poroelastic deformation in calderas
AU: * Christiansen, L B
EM: lchristi@usgs.gov
AF: U.S. Geological Survey, 345 Middlefield Rd., Menlo Park, CA 94025 United States
AU: Hsieh, P
EM: pahsieh@usgs.gov
AF: U.S. Geological Survey, 345 Middlefield Rd., Menlo Park, CA 94025 United States
AU: Hurwitz, S
EM: shaulh@usgs.gov
AF: U.S. Geological Survey, 345 Middlefield Rd., Menlo Park, CA 94025 United States
AU: Ingebritsen, S E
EM: seingebr@usgs.gov
AF: U.S. Geological Survey, 345 Middlefield Rd., Menlo Park, CA 94025 United States
AB: Many observations suggest that hydrothermal fluids may play more of a role than commonly acknowledged in controlling and maintaining surface uplift and subsidence in large calderas such as Long Valley and Yellowstone in western USA. As an alternative to traditional models that invoke volume change of a discrete source embedded either in an elastic or viscoelastic media, we use numerical simulations to quantify the role of aqueous fluids and CO2 to account for ground-surface displacements. We couple the non-isothermal, multi-phase groundwater flow model TOUGH2 (Pruess, 1991) with a thermo-poroelasticity model BIOT2 (Hsieh, 1996) to quantify the relation between groundwater dynamics and ground surface deformation. The model domain consists of a cylinder that is 50 km in diameter and 5 km in height. Hydrothermal fluids are injected at variable rates into the center of the base of the cylinder. A sensitivity analysis is carried out to examine the role of various parameters on groundwater pressure distribution and the resulting rates of vertical and horizontal ground surface displacements. Initial results suggest that small changes in fluid injection rate, rock permeability, and temperature distribution may lead to significant variations in ground surface displacement rates and magnitudes. Some of the simulated uplift rates are similar to those observed in large calderas. The combination of forward numerical modeling and calibration to match relevant geophysical data can help constrain the mode of caldera deformation.
DE: 1207 Transient deformation (6924, 7230, 7240)
DE: 1835 Hydrogeophysics
DE: 8419 Volcano monitoring (7280)
DE: 8424 Hydrothermal systems (0450, 1034, 3017, 3616, 4832, 8135)
DE: 8440 Calderas
SC: Geodesy [G]
MN: Fall Meeting 2005