Area-Specific Seismic Noise Reference Curves in an Urban Volcanic Environment: The Campi Flegrei Case

The study investigates the seismic ambient noise within the Campi Flegrei caldera (Na-ples, Italy) to improve the detection capability and reliability of the local earthquake moni-toring system managed by the INGV, Osservatorio Vesuviano. It focuses on the spectral characteristics and spatial variability of the ambient noise field, aiming to identify the dominant frequency bands that control signal detectability and to provide key information for the optimization of the monitoring network. Due to the dense urban environment sur-rounding the caldera, seismic recordings are often contaminated by high anthropogenic noise, which can mask low-magnitude volcanic or seismic signals. Power Spectral Density (PSD) analysis was applied to evaluate background noise levels at several broadband sta-tions belonging to both the permanent and temporary seismic networks over the period January 2022 to January 2023. The resulting PSD estimates were compared with the global Peterson noise models to assess station performance and environmental conditions. Re-sults show significant variability among stations, related to local human activity, proxim-ity to infrastructure and different installation settings (buried vs. surface). The study em-phasizes the importance of continuous noise monitoring to ensure high-quality seismic data, support optimal station siting, and refine monitoring strategies in densely populated volcanic regions such as Campi Flegrei, where the reliable detection of low-amplitude seismic and volcanic signals is essential.