Technical Papers and Presentations

Multi-parameter monitoring techniques, combined with robust mathematical models, are crucial for effective volcano monitoring and early warning to civil authorities and the public. This work focuses on the modeling of ground deformation, an indispensable component for any volcano monitoring strategy. A key assumption behind geodetic monitoring is that ground deformation of the Earth's surface reflects tectonic and volcanic processes at depth (e.g., fault slip and/or mass transport) transmitted to the surface through the mechanical properties of the crust. Several analytical and numerical mathematical models, available in the literature, can be used to fit ground deformation and infer source location, depth, and volume change. Despite the skepticism regarding the usefulness of analytical models because of the simplifications (e.g., the assumption that the crust is a homogenous, isotropic, elastic medium, flat-half space) that make the set of differential equations describing the problem tractable, they remain valuable. On the other hand, numerical Finite Element Method (FEM) models, because of their ability to implement a more realistic representation of the crust and topography, are perceived to better represent volcanic processes and lead to a more accurate interpretation and understanding of surface deformation in active volcanic areas. Constraining crustal and source complexities, such as the real shape of subsurface layers and their stiffness, as well as the details of the shape of magmatic sources, remains challenging. This limited and uncertain knowledge means that FEM models may require a dedicated study not only for every individual volcano, but also for individual events. In contrast, analytical models have a more universal value and may offer rapid insight into the source of volcano deformation. Volcano observatories need to determine quickly whether deformation sources are active to inform Civil Defense or other authorities in cases of imminent risk to the public. The sources are detected as changes in the parameters of a pressurized magma body model that might imply a magma reservoir that is changing or ascending. In this work, we compare the interpretation of ground deformation measured at Nevado del Ruiz (Colombia) and Augustine volcano (Alaska) using 3D FEM COMSOL Multiphysics models and equivalent analytical models implemented in MATLAB. The FEM models include complexities like topography, and vertical and lateral heterogeneities. To avoid possible numerical and coding errors, the analytical models have been verified against numerical models developed in COMSOL Multiphysics. Preliminary results shows that analytical solutions are far from obsolete, and numerical methods may never entirely replace them. Rather, analytical, and numerical approaches are complementary and define two end members of a wide range of modeling techniques, with the optimal technique depending on the specific purpose.