Poroelastic Deformation at Soufrière Hills: A New Perspective on Volcano Deformation Dynamics 

Abstract

Volcano deformation studies often neglect the role of the porous, crystal-rich magma reservoirs in modulating surface deformation patterns. Our study examines the current deformation at Soufrière Hills Volcano (SHV) in its ongoing intra-eruptive unrest, with an emphasis on the influence of a mush-dominated, poroelastic magma reservoir. Using 3D finite element models constrained by 14 continuous GPS stations, our findings indicate deformation caused by ongoing melt injection into a low permeability (4.7 x 10-10 m2) reservoir with the injection source located at 16.5 km depth below sea level. Our models show that the melt supply likely decreased linearly from ~1.9 to ~0.3 m3/sec between 2010 and 2022, fitting the recorded decreasing GPS displacement rates. Projective modelling indicates a potential full cessation in melt injection around mid-2024 ± 2 years, but poroelastic melt diffusion will continue, deforming the surface and potentially impacting the stability of the reservoir. Future expansions of this study will incorporate dynamic magma property changes from existing thermodynamic models to represent pressure, temperature and volatile-dependent magma evolution. Our study sheds light on the understanding of deformation patterns at volcanoes, particularly those with crystal-abundant magma reservoirs like SHV.