Numerical models of caldera deformation: Effects of multiphase and multicomponent hydrothermal fluid flow

Abstract

[1] Ground surface displacement (GSD) in large calderas is often interpreted as resulting from magma intrusion at depth. Recent advances in geodetic measurements of GSD, notably interferometric synthetic aperture radar, reveal complex and multifaceted deformation patterns that often require complex source models to explain the observed GSD. Although hydrothermal fluids have been discussed as a possible deformation agent, very few quantitative studies addressing the effects of multiphase flow on crustal mechanics have been attempted. Recent increases in the power and availability of computing resources allow robust quantitative assessment of the complex time-variant thermal interplay between aqueous fluid flow and crustal deformation. We carry out numerical simulations of multiphase (liquid-gas), multicomponent (H 2 O-CO 2 ) hydrothermal fluid flow and poroelastic deformation using a range of realistic physical parameters and processes. Hydrothermal fluid injection, circulation, and gas formation can generate complex, temporally and spatially varying patterns of GSD, with deformation rates, magnitudes, and geometries (including subsidence) similar to those observed in several large calderas. The potential for both rapid and gradual deformation resulting from magma-derived fluids suggests that hydrothermal fluid circulation may help explain deformation episodes at calderas that have not culminated in magmatic eruption.

Bottom pressure signals at the TAG deep‐sea hydrothermal field: Evidence for short‐period, flow‐induced ground deformation

“…The deformation displacements we observed ( 13 mm) are modest compared to observations and models for subaerial geothermal fields [e.g., De Natale et al, 2001; Hutnak et al, 2009], and the cycle periods are similar to many geyser eruption intervals, which are typically 10s of minutes up to several hours, and which can be associated with systematic inflation/deflation GSD cycles [Nishimura et al, 2006]. The strict analogy to geysers is probably limited by the fact that the volume expansion associated with phase transitions is $500 times smaller in the deep-sea environment at TAG compared to subaerial geothermal fields [e.g., Driesner, 2007], but the concept of highly-regular pressure cycles associated with the steady flux of fluid and heat into a sub-surface reservoir appears to provide the most likely explanation for our observations.…”

Numerical models for ground deformation and gravity changes during volcanic unrest: simulating the hydrothermal system dynamics of a restless caldera

“…(5). This is known as one-way coupling between hydrological and mechanical models, as used previously by a number of studies (Hurwitz et al, 2007;Hutnak et al, 2009;Rinaldi et al, 2010;Todesco et al, 2010). It is a simplified approach compared with a fully coupled model that also takes into account the influence of stress and strain on permeability and porosity during the simulation (Neuzil, 2003;Rutqvist, 2011).…”

“…For caldera volcanoes in particular, earlier models focused on explaining ground deformation by magma emplacement (Anderson, 1937;Mogi, 1958;Bonafede et al, 1986;Bianchi et al, 1987;De Natale et al, 1991). Beside this interpretation, more recently models also consider the perturbation of hydrothermal systems (by pore pressure changes, variations in gas saturation and thermal expansions) as a possible (additional) source of spatio-temporal variations in deformation and gravity signals (Casertano, 1976;Gottsmann et al, 2003Gottsmann et al, , 2006aTodesco et al, 2003Todesco et al, , 2010Chiodini et al, 2007;Hurwitz et al, 2007;Hutnak et al, 2009;Ingebritsen et al, 2010;Rinaldi et al, 2010Rinaldi et al, , 2011Troiano et al, 2011).…”

“…Todesco and Berrino, 2005;Hurwitz et al, 2007;Hutnak et al, 2009;Todesco et al, 2010;Rouwet et al, 2014) from those related to magma movement towards the surface (e.g. Amoruso et al, 2008Amoruso et al, , 2014bWoo and Kilburn, 2010;Trasatti et al, 2011).…”

Poroelastic responses of confined aquifers to subsurface strain and their use for volcano monitoring

“…Numerical modelling of pressure changes in hydrological systems has focused on pressure and temperature transients in hydrothermal systems and resulting ground deformation due to the injection of hot magmatic fluids, using one-way coupling of solid deformation and porous flow (e.g. Todesco et al, 2004;Hurwitz et al, 2007;Hutnak et al, 2009;Rinaldi et al, 2010;Fournier and Chardot, 2012). Rutqvist et al (2002) have developed a two-way coupled code and applied it to problems related to carbon dioxide injection in aquifers and the disposal of nuclear waste in porous media.…”