Impact of Crustal Rheology on Temperature‐Dependent Viscoelastic Models of Volcano Deformation: Application to Taal Volcano, Philippines

Abstract

We use ALOS-1 interferometric synthetic aperture radar data spanning the period of 2007-2011 to obtain time-dependent ground deformation data over Taal caldera related to the 2010-2011 volcanic unrest, which did not lead to an eruption. We employ finite element models that account for subsurface thermomechanical properties to test for viscoelastic deformation. We also examine the variability of crustal rheological parameters of the temperature-dependent Arrhenius formulation for viscosity, to investigate the effects on surface deformation. Deformation at Taal is observed to be time dependent and explained by a linear rate of pressure increase in a shallow magma reservoir at 5-km depth within a hot and viscoelastic upper crust. The best-fitting rheological properties of the local setting are consistent with either a felsic or hydrothermally altered uppermost crust. We show the significantly different effects that the variation of rheological parameters has on surface deformation, highlighting the importance of incorporation into future studies of deformation at different volcanic settings.Recent viscoelastic models of volcano deformation have used the Arrhenius formulation (see section 3.3.3) to estimate the viscosities of the medium (e.g., Gregg et al., 2012;Hickey et al., 2015), employing commonly used variables within the formulation that are potentially representative of the composition and temperatures of the subsurface, without full exploration of their potential values. Understanding the possible variations within these parameters along with their implications is critical to depict realistic rheological scenarios. It is also crucial for future studies that aim to understand crustal deformation, magma reservoir failure, intrusion propagation, and eruption forecasting.

Ground Deformation After a Caldera Collapse: Contributions of Magma Inflow and Viscoelastic Response to the 2015–2018 Deformation Field Around Bárðarbunga, Iceland

“…Other studies apply spatially varying viscosity models, such as Morales Rivera et al. (2019) used for the 2010–2011 Taal volcano unrest and Del Negro et al. (2009) used for the 1993–1997 Etna volcano inflation.…”

“…Due to elevated crustal temperature in volcano roots, viscoelastic relaxation may be pronounced in relation to large‐volume magma transfer events. Multiple studies have focused on viscoelastic deformation related to rifting events and volcanic eruptions, for example, following dyking events during the 2005–2010 Dabbahu rifting episode at Afar (Hamling et al., 2014), at the Kutcharo caldera, Japan (Yamasaki et al., 2018), at Taal volcano (Morales Rivera et al., 2019) and Laguna del Maule volcano in Chile (Novoa et al., 2019). During the 2005–2010 Dabbahu rifting episode, continuous displacements were observed by Interferometric Synthetic Aperture Radar (InSAR) and Global Navigation Satellite System (GNSS).…”

“…Morales Rivera et al. (2019) explain the 2010–2011 unrest deformation at Taal volcano using a temperature‐dependent spatially varied viscoelastic model. Novoa et al.…”

The Influence of Viscoelastic Crustal Rheologies on Volcanic Ground Deformation: Insights From Models of Pressure and Volume Change

“…With the SLS model, we have demonstrated that the relative weightings of the elastic arm ( μ 0 ) and the Maxwell arm ( μ 1 ) strongly influence both the asymptote magnitude and the timescale of convergence; however, there is little experimental evidence to suggest how these values should be allocated other than on the basis to reduce misfit. As a result, an equal weighting of 0.5 is most common (e.g., Del Negro et al, ; Gottsmann & Odbert, ; Hickey et al, , , ; Le Mével et al, ; Morales Rivera et al, ). However, insight into the weighting of the fractional shear moduli may be gained from the ratio of instantaneous (elastic) to time‐dependent (viscous) deformation (Figure g), and so it may be possible to derive alternative relative contributions from deformation time series, but the use should be carefully considered.…”

Changes in Atmospheric, Meteorological, and Ocean Parameters Associated with the 12 January 2020 Taal Volcanic Eruption

“…During the last 40 years, no eruptive activity was recorded; given the past eruption history, an unusual quiescence period was realized by the scientists. Seismological [54,55], geochemical [56], electromagnetic [55,57], thermal [52,58], and InSAR crustal deformation measurement [59] techniques were used to monitor activities of the Taal volcano. Efforts were made to map the 3-D structure and monitor the volcanic activities and observations of geophysical parameters (magnetic, electric, tilt, resistivity, ground and water temperature).…”