Investigating the role of topography and attenuation in volcanic areas by testing different structural models of the Campi Flegrei

The Campi Flegrei caldera, with its complex volcanic structure, represents an intriguing challenge for understanding seismic wave propagation. This study presents forward simulations of seismic wave propagation in the caldera area performed by using the spectral element method software SPECFEM3D (Peter et al., 2011). Moment tensor solutions for three seismic events that occurred between May and June 2024, including the Md 4.4 Solfatara earthquake, were considered. Simulations were performed using five different wavespeed models: (1) a 1D model without topography; (2) the same model incorporating the regional topography; (3) the local tomographic model from Giacomuzzi et al. (2024); (4) a 3D model including local attenuation from Calò & Tramelli (2018); and (5) the Italian 3D tomographic model Im25 by Magnoni et al. (2022).

Our approach aims to compare these models for the same seismic sources, in order to highlight the key factors influencing waveform fit between observed and synthetic data. Implementing high-resolution surface topography —characterized by volcanic structures, depressions, and abrupt variations—is crucial to improve waveform fit and reproduce seismogram behavior. Moreover, the results highlight the importance of adopting tomographic models with tailored attenuation and 3D velocity structures that effectively capture the lateral heterogeneities of such a complex area. This is especially crucial when modeling the Campi Flegrei caldera characterized by solidified intrusions and partially melted regions in order to achieve more accurate regional predictions.

Given the coastal setting of the considered area, we also investigate whether the presence of a water layer (i.e., acoustic elements), absent in current simulations, might influence the quality of the fit between observed and synthetic data. To this aim, we explore a simplified scenario that would be representative of the studied region.