Volcanoes undergoing unrest often produce displacements at the ground surface,
providing an important window to interpret the dynamics of the underlying magmatic system. The
thermomechanical properties of the surrounding host rock are expected to be highly heterogeneous,
with key physical parameters having a strong dependence on ...
Volcanoes undergoing unrest often produce displacements at the ground surface,
providing an important window to interpret the dynamics of the underlying magmatic system. The
thermomechanical properties of the surrounding host rock are expected to be highly heterogeneous,
with key physical parameters having a strong dependence on temperature. Deformation models that
incorporate nonelastic rheological behaviors are therefore heavily reliant on the assumed thermal
conditions, and so it is critical to understand how the thermomechanical crustal structure affects the
observed deformation field. Here, we use a series of thermo-viscoelastic Finite Element models to explore
how variations in thermal constraints (i.e., reservoir temperature and background geothermal gradient)
affect surface displacement patterns when using the Maxwell and Standard Linear Solid (SLS) viscoelastic
configurations. Our results demonstrate a strong variability in the viscoelastic deformation response when
changing the imposed thermal constraints, caused by the partitioning of deformation and the dissipation
of induced stresses. When using the SLS rheology, we identify that cumulative long-term displacements
can vary by over 20%, relative to a reference model with a reservoir temperature of 900°C and background
geothermal gradient of 30 K km−1. The relative change increases to a maximum of 35% when thermal
weakening of the Young's modulus is also considered. Contrastingly, the deformation patterns of the
Maxwell rheology are governed by unbounded displacements and complete stress relaxation. Ultimately,
we outline that uncertainties in the thermal constraints can have a significant impact on best-fit source
parameters (e.g., size and depth) and overpressure/volume-change loading histories inferred from thermoviscoelastic models.