Coupled magmatic-hydrothermal processes during ongoing inflation at Askja volcano

Askja volcano's ongoing inflation since August 2021 (+85 cm uplift) presents a unique opportunity to study coupled magmatic-hydrothermal processes during sustained volcanic unrest. Concurrent observations of seismic velocity decrease (dv/v) at ~2 km depth and decreasing surface thermal anomalies (>1 K) suggest that hydrothermal circulation actively responds to magmatic intrusions. In this project, we aim to understand how hydrothermal processes modulate surface deformation and thermal emissions during magmatic injections at depth using coupled thermo-poroelastic, Finite Element Method (FEM), numerical models. Our models (built with COMSOL Multiphysics) integrate solid mechanics, Darcy flow, and heat transfer in porous media, representing a permeable hydrothermal reservoir above a sill intrusion at 2.6 km depth. Sill geometry is constrained by elastic inversions of geodetic data from Parks et al. (2024). Permeability depends on effective stress (exponential reduction under compression), temperature (exponential increase with heating), and volumetric strain (cubic modification of porosity).

Long-term simulations provide initial conditions with background thermal and hydraulic gradients, followed by a 4-year perturbation simulating the magma intrusion through increased heat flux and a prescribed displacement rate (0.21 m/year). Results show that compression at depth creates a low-permeability seal, trapping heat and pressurized fluids below. Beneath the seal, temperature increases, consistent with observed dv/v decreases at 2 km depth; while above the seal, reduced fluid circulation causes surface cooling of less than 1 K, explaining the decrease in thermal anomalies detected in satellite observations.

Our preliminary results suggest that multi-parameter observations at Askja (geodetic, seismic velocity, thermal anomalies) can be explained through coupled thermo-poroelastic processes, showing that hydrothermal system dynamics should be considered to interpret  monitoring data during volcanic unrest.