Geosciences, Vol. 15, Pages 245: Efficiency of Multi-Terminators Method to Reveal Seismic Precursors in Sub-Ionospheric VLF Transmitter Signals: Case Study of Turkey–Syria Earthquakes Mw7.8 of 6 February 2023

Geosciences doi: 10.3390/geosciences15070245

Authors:
Mohammed Y. Boudjada
Patrick H. M. Galopeau
Sami Sawas
Giovanni Nico
Hans U. Eichelberger
Pier F. Biagi
Michael Contadakis
Werner Magnes
Helmut Lammer
Wolfgang Voller

This work presents an analysis of the sub-ionospheric VLF transmitter signal disturbances which were detected more than one week before the Turkey–Syria EQ occurrence. We have applied the multi-terminator method when considering amplitude and phase variations of the TBB transmitter signal (Turkey), selected because of a good signal to noise ratio for the amplitude, a stable phase variation, and a ray-path propagation crossing the pre-seismic sensitive region, estimated from the combination of the Dobrovolsky area and the Fresnel zone. New spectral features, i.e., inflexions and jumps, are considered in this study, besides the minima and maxima investigated in. The spectral occurrence probabilities are derived at three specific locations: Graz facility, TBB station and EQ epicenter. We show that two main precursors occurred from 27 to 30 January, and from 31 January to 3 February. More important are the prior precursors detected from 23 January to 25/26 January, where anomaly fluctuations were found to be similar to those at the EQ epicenter area, approximately. A forecasting model is proposed, in which the main steps can provide, in the presence of spectral anomalies, first hints regarding the longitudinal locations of the seismic preparation zone.

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Mohammed Y. Boudjada www.mdpi.com