Spectral Characterization and Spatiotemporal Variability of the Background Seismic Noise in Italy

Abstract

In this study, we assess the spectral characteristics of seismic noise at the sites of the Italian Seismic Network and its spatio-temporal variability. The evaluation of noise is crucial for the assessment of the detection capability of a seismic network. We selected a set of 233 stations, those equipped with broadband velocimeters (with corner period (Formula presented.) 40 s) and operating continuously for at least four consecutive years. The analysis was carried out in the frequency band from 0.025 to 30 Hz, in accordance with the seismic sensors bandwidth. We estimated the Power Spectral Density (PSD) of the seismic noise for fixed temporal windows and then we calculated the Probability Density Functions (PDF) at each station. Exploiting the large data set available, we have been able to: (a) describe the characteristics of the noise power at each site; (b) investigate both temporal and spatial variations of the background noise, revealing correlations of the noise levels with natural and anthropogenic noise sources; (c) propose an empirical relationship linking the “microseismic” noise (i.e., 0.12–1.2 Hz) with the geographical features of the site hosting the seismic station; (d) establish the baselines of a new seismic noise model that could be considered as a new reference for the Italian territory.