Ionospheric turbulence from TEC variations and VLF/LF transmitter signal observations before and during the destructive seismic activity of August and October 2016 in Central Italy

Abstract

In this paper we investigate the ionospheric turbulence from observations of TEC variations as well as from VLF/LF transmitter signal observations before and during the disastrous seismic activity of August and October 2016 in Central Italy. The Total Electron Content (TEC) data of 8 Global Positioning System (GPS) stations of the EUREF network, which are being provided by IONOLAB (Turkey), were analysed using Discrete Fourier Analysis in order to investigate the TEC variations. The data acquired for VLF/LF signal observations are from the receiver of Thessaloniki (40.59N, 22,78E), Greece, which monitor the VLF/LF transmitters of the International Network for Frontier Research on Earthquake Precursors (INFREP). A method of normalization according to the distance between the receiver and the transmitter is applied on the above data and then they are processed by the Hilbert Huang Transform (HHT) to produce the corresponding spectra for visual analysis. The results of both methods indicate that the High- Frequency limit fo, of the ionospheric turbulence content, increases as the site and the moment of the earthquake occurrence is approaching, pointing to the earthquake locus.

Foreword: Advances in Multi-Parametric, Time-Dependent Assessment of Seismic Hazard and Earthquakes Forecast

“…To the second group of papers belong the papers by Arabelos et al [2020], Contadakis et al [2020], Ouzounov et al [2020, who combine different parameters and/or measuring methods to reduce space-time forecast volumes (from regional/annual to very local/short-term scales) as well as those by Huang et al [2020] mostly devoted to better discriminate among signals possibly related to earthquake occurrence.…”

“…The same ionospheric parameters are investigated by Contadakis et al [2020], in a limited period of time (from 24/07/2016 to 25/09/2016 from 25/10/2016 to 25/11/2016) around the major earthquakes that hit Central Italy (Amatrice sequence) on August 24 th (M W = 6.2, 42.71°N, 13.17°E), October 26 th (M W = 6.1, 42.96°N, 13.07°E) and October 30 th (M W = 6.6, 42.86°N, 13.09°E), emphasizing their potential in contributing to reduce (up to 15 days) the forecast time window.…”