ON THE DETECTION OF ANOMALIES IN TIME SERIES OF VLF SIGNALS RELATED TO SEISMIC ACTIVITY

In this work we present an application of the Perceptually Important Points (PIP) technique for the analysis of time series of VLF signals collected during some earthquakes (Mw = 5.0–6.0) occurred in the European area. The aim of the analysis is to detect “anomalies” of VLF signals with respect to the normal variations of the data trends; these anomalies could reveal possible radio precursors of the earthquakes. Since 2009, several radio receivers have been installed throughout Europe in order to realize the INFREP European radio network for studying the VLF (10–60 kHz) and LF (150–300 kHz) radio precursors of earthquakes (Biagi et al., 2011), (Righetti et al., 2012). The analysis has been applied to earthquakes with Mw ≥ 5.0 located inside the 5th Fresnel zone defined by each receiver and transmitter or inside a circle with a 300km radius around each receiver or transmitter. The time series which have been analyzed are referring to earthquakes that occurred on 2009-09-06 (Mw = 5.6), 2010-02-06 (Mw = 5.0), 2010-03-08 (Mw = 6.0), and 2020-01-30 (Mw = 5.6)