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JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 112, B02206, doi:10.1029/2006JB004689, 2007

Hydrothermal fluid flow and deformation in large calderas: Inferences from numerical simulations

Shaul Hurwitz

U.S. Geological Survey, Menlo Park, California, USA


Lizet B. Christiansen

U.S. Geological Survey, Menlo Park, California, USA


Paul A. Hsieh

U.S. Geological Survey, Menlo Park, California, USA


Abstract

Inflation and deflation of large calderas is traditionally interpreted as being induced by volume change of a discrete source embedded in an elastic or viscoelastic half-space, though it has also been suggested that hydrothermal fluids may play a role. To test the latter hypothesis, we carry out numerical simulations of hydrothermal fluid flow and poroelastic deformation in calderas by coupling two numerical codes: (1) TOUGH2 [Pruess et al., 1999], which simulates flow in porous or fractured media, and (2) BIOT2 [Hsieh, 1996], which simulates fluid flow and deformation in a linearly elastic porous medium. In the simulations, high-temperature water (350°C) is injected at variable rates into a cylinder (radius 50 km, height 3–5 km). A sensitivity analysis indicates that small differences in the values of permeability and its anisotropy, the depth and rate of hydrothermal injection, and the values of the shear modulus may lead to significant variations in the magnitude, rate, and geometry of ground surface displacement, or uplift. Some of the simulated uplift rates are similar to observed uplift rates in large calderas, suggesting that the injection of aqueous fluids into the shallow crust may explain some of the deformation observed in calderas.

Received 10 September 2006; accepted 17 October 2006; published 24 February 2007.

Keywords: numerical simulation; caldera; hydrothermal; deformation; ground surface displacement; poroelastic.

Index Terms: 8424 Volcanology: Hydrothermal systems (0450, 1034, 3017, 3616, 4832, 8135); 8440 Volcanology: Calderas; 8045 Structural Geology: Role of fluids; 0560 Computational Geophysics: Numerical solutions (4255); 1829 Hydrology: Groundwater hydrology.

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Citation: Hurwitz, S., L. B. Christiansen, and P. A. Hsieh (2007), Hydrothermal fluid flow and deformation in large calderas: Inferences from numerical simulations, J. Geophys. Res., 112, B02206, doi:10.1029/2006JB004689.