Modeling of surface deformation in volcanic areas: The 1970–1972 and 1982–1984 crises of Campi Flegrei, Italy

Abstract

Campi Flegrei is a densely inhabited volcanic area within a caldera, 12–14 km in diameter, immediately west of Naples, Italy. In 1970–1972 and in 1982–1984, Campi Flegrei experienced considerable ground surface deformation producing a bulge about 3.5 m high at its peak. In the two inflation episodes the point of maximum uplift did not change, coinciding with the caldera center, about which the displacements exhibited radial symmetry. The 1982–1984 uplift was accompanied by considerable seismic activity. Gravity changes have been interpreted as reflecting the occurrence of a subvertical magmatic intrusion. Volcanological, petrological, and geophysical data point to the existence of a shallow magma chamber just beneath the center of the caldera. We assume that the observed surface displacements are the response of an essentially elastic medium to a pressure increase in the magma chamber. Static deformation is calculated by using a finite‐element method, assuming axial symmetry around a vertical axis through the caldera center. The role played by various components of the model, geometry, boundary conditions, elastic properties, is analyzed. It is shown that models assuming uniform elasticity are inadequate. Therefore the major volcanotectonic features as well as the influence of temperature and pressure on the elastic properties are taken into account. The results of various more complex models are presented. It is suggested that a progressively fractured zone, whose size and shape depend also on the possible occurrence of magmatic intrusions, may explain the observed surface displacements and the other data collected at Campi Flegrei. It is suggested that the 1970–1972 uplift was possibly accompanied by larger‐scale changes in the stress field.

Numerical models for ground deformation and gravity changes during volcanic unrest: simulating the hydrothermal system dynamics of a restless caldera

“…For caldera volcanoes in particular, earlier models focused on explaining ground deformation by magma emplacement (Anderson, 1937;Mogi, 1958;Bonafede et al, 1986;Bianchi et al, 1987;De Natale et al, 1991). Beside this interpretation, more recently models also consider the perturbation of hydrothermal systems (by pore pressure changes, variations in gas saturation and thermal expansions) as a possible (additional) source of spatio-temporal variations in deformation and gravity signals (Casertano, 1976;Gottsmann et al, 2003Gottsmann et al, , 2006aTodesco et al, 2003Todesco et al, , 2010Chiodini et al, 2007;Hurwitz et al, 2007;Hutnak et al, 2009;Ingebritsen et al, 2010;Rinaldi et al, 2010Rinaldi et al, , 2011Troiano et al, 2011).…”

Modeling of recent volcanic episodes at Phlegrean Fields (Italy): geochemical variations and ground deformation

“…Even though early authors already recognized the potential role of hydrothermal fluid circulation in these events (Olivieri del Castillo and Quagliariello, 1969;Casertano et al, 1976), modelling efforts mostly focused on the mechanical aspects at first, describing the bradyseismic phenomenon as the result of a pressure build-up inside a magma chamber (Caputo, 1976;Casertano et al, 1976;Corrado et al, 1976;Berrino et al, 1984;Bonafede et al, 1986;Bianchi et al, 1987). Many of these authors describe the magma chamber as a pressure source embedded in a homogeneous half space, with elastic or visco-elastic properties.…”

Recognizing and tracking volcanic hazards related to non-magmatic unrest: a review

“…The discussion as to whether the unrest at Campi Flegrei since the 1980's is magmatic (Bianchi et al 1987;Bonafede et al 1986;Gottsmann et al 2006), or non-magmatic (Casertano et al 1976;Bonafede 1991;De Natale et al 1991;Gaeta et al 1998) is still ongoing. Recently, the tendency to explain the uplift by the expansion of the underlying hydrothermal system has become more plausible as it is supported by decade-long monitoring time series (geochemistry, geodesy, geophysical surveys) (Chiodini et al 2001Todesco et al 2003), even though the deformation pattern may be explained by alternative models (e.g., Amoruso et al 2014).…”