dMODELS. A free software package to model volcanic deformation

Shallow magma accumulation in the crust often results in slight movements of the ground surface that can be measured using standard land-surveying techniques or satellite geodesy. Volcano geodesy uses measurements of crustal deformation to investigate volcano unrest and to search for magma reservoirs beneath active volcanic areas. 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. Measurements and modeling of ground deformation are an indispensable component for any volcano monitoring strategy. The critical questions that emerge when monitoring volcanoes are how to (a) constrain the source of unrest, (b) improve the assessment of hazards associated with the unrest and (c) refine our ability to forecast volcanic activity. A number of analytical and numerical mathematical models are available in the literature that can be used to fit ground deformation to infer source location, geometry, depth and volume change. Analytical models offer a closed-form description of the volcanic source. This allows us, in principle, to readily infer the relative importance of any of the source parameters. The careful use of analytical models, together with high quality data sets can provide valuable insights into the nature of the deformation source (e.g., Battaglia and Hill, 2009). The simplifications that make analytical models tractable, however, may result in misleading interpretations. Sources are approximated by pressurized cavities in homogenous, elastic half-spaces filled with fluids. Although actual magmatic sources are certainly more complex, this approach can mimic the stress or potential field of the magma or other fluid sources beneath a volcano. The use of numerical models (e.g., finite element models) allows for evaluation of more realistic source characteristics and crustal properties (e.g., vertical and lateral mechanical discontinuities, complex source geometries, topography) but may require expensive proprietary software and powerful computers.