LINKING THE FLOW DYNAMICS IN MAGMA CHAMBERS AND DYKES TO THE GEOPHYSICAL OBSERVATIONS ON THE SURFACE

One of the most relevant problems in volcanology is the capability to detect and recognize signals diagnostic of deep magma dynamics. Laboratory analyses of volcanic products provide extensive evidence of periodic arrivals of magma inside pre-existing magma chambers, often shortly preceding a volcanic eruption. Early warning at volcanoes requires therefore that such potentially hazardous events be monitored and recognized. With that purpose, we have developed a finite element parallel C++ code (GALES) which solves the mass, momentum and energy equations for multi-component homogeneous mixtures made of gas and liquid, in the compressible and incompressible flow regimes. Magma properties are computed on the basis of local P-T-X conditions. Here we present numerical results showing the time-space-dependent dynamics of magma chamber replenishment for the geometrically complex systems of Campi Flegrei and Etna. Such results reveal discontinuous pulses related to ascent of light and sink of dense magma. While the mass is re-distributed, the pressure in the chamber oscillates with ultra-long-periods of the order of minute(s). Spatial integration of the mass contribution to the local gravimetric field gives the time-dependent gravity changes associated with the simulated dynamics. The normal and deviatoric stress terms computed at the fluid-rock boundaries are then converted to forces representing the source of ground displacement, by assuming one-way fluid-rock coupling. Here we follow two different procedures: i) we directly compute the classical Stoke’s solution to the elastodynamic Green’s functions in homogeneous half-space, or ii) we employ, in cooperation with C. Bean and G. O’Brien (University College Dublin), a numerical code based on discrete elastic lattice method, accounting for free surface, topographic profile, and heterogeneous rock properties. The results show the characteristics of ground deformation and seismicity associated to magma chamber replenishment dynamics, in terms of amplitude, frequency content, and wave forms. The initiated production of numerical results pertaining to a spectrum of conditions at different volcanoes will provide the theoretical basis and the paradigms for physically sound short-term volcanic hazard forecast and early warning evaluation systems.