Signals from the Campi Flegrei hydrothermal system: Role of a ‘‘magmatic’’ source of fluids

This is a parametric study that was carried out to investigate the signals generated by a
hydrothermal system fed by a pulsating source of magmatic fluids. This study focuses on
the effects that selected properties of the source have on the evolution of hydrothermal
activity at Campi Flegrei, Italy. Numerical simulations are carried out to describe a
multiphase and multicomponent hydrothermal system. Each simulation describes a short
unrest phase, followed by a prolonged quiet period. During the unrest, specific properties
of the fluid source (flow rate, fluid composition, source size, and unrest duration) are
modified with respect to selected baseline values. The evolution of the system is tracked
by looking at two parameters that can be monitored in active volcanic areas: the
composition of fumarolic gases and gravity changes. The results describe the temporal
evolution of these two observables and allow comparisons of the effects of different source
properties. All of the simulated unrest events cause measurable changes in gas
composition and gravity. For the geometry and system properties considered, these
changes always last beyond the end of the unrest period, and can often persist for
decades. Fluid flow rate is the source property that mostly affects the observable
evolution. Gravity is more sensitive to source properties than gas composition, and it
undergoes the largest and quickest changes. The results also highlight the major role that
rock properties and initial conditions have in the evolution of these observable signals.

Department of Civil Protection

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