autores Bezzeghoud, M. Biagi, P.F. Righetti, F. Maggipinto, T. Schiavulli, L. Ligonzo, T. Ermini, A. Moldovan, I.A. Aksoy-Aksel, A.
palavras-chave Precursors of earthquakes Principal component technique Standard deviation trends VLF and LF radio receivers Wavelet spectra analysis