On the effects of 3-D mechanical heterogeneities at Campi Flegrei caldera, southern Italy

Campi Flegrei caldera, located near the highly populated city of Naples, southern Italy, is characterized by long-term subsidence punctuated by fast uplift phases. Most of the interpretations of the ground deformation are still based on standard models that assume the lithosphere to behave as a homogeneous half-space. However, several geophysical investigations show the presence of vertical and lateral heterogeneities, especially in the shallow subsurface, which might have an effect on the interpretation of the surface displacements. Our 3-D finite element models, constrained by seismic tomography to take into account the realistic distribution of mechanical heterogeneities, demonstrate that at Campi Flegrei the assessment of the source location is independent of the consideration of 3-D heterogeneities, while the evaluation of its strength is overestimated. Thus, we propose an approach that still allows use of standard homogeneous half-space models but accounts for 3-D heterogeneity effects. This procedure, applied to the deformation field revealed by Differential Synthetic Aperture Radar Interferometry (DInSAR) over the past 16 years, provides new insights for the understanding of the ground displacements observed at Campi Flegrei caldera. This work provides an approach for a quantitative evaluation of the effects of mechanical heterogeneities on surface deformation. Analogous procedures can be also applied in other volcanic areas where, similar to Campi Flegrei caldera, a priori information on the mechanical heterogeneities distribution is available.