Effectiveness of the Relative δ-Barbier Parameter in the Search for Ionospheric Precursors of Earthquakes

A study of temporal variations of the complex relative δ-Barbier parameter (δ Barbier ) was carried out to evaluate its effectiveness in the search for seismo-ionospheric precursors. For this purpose, its behavior (according to 15-min measurements of ionospheric parameters) was considered before two strong earthquakes for which seismo-ionospheric precursors had already been detected. The first earthquake (with magnitude M = 6.3) occurred on April 6, 2009 (L’Aquila, Italy) at an epicentral distance of ~93 km from the Rome ground-based vertical ionospheric sounding station, and the second earthquake (with magnitude M = 7.2) occurred on January 30, 2016, while its epicenter was ~117 km from the ground-based vertical ionospheric sounding station located on the territory of the Paratunka Kamchatka complex geophysical observatory. In both cases, specific features were identified in the behavior of the δ Barbier parameter that coincided in time with the previously detected ionospheric precursors of these earthquakes. This allows us to conclude that the effectiveness of using the δ Barbier parameter in the search for seismo-ionospheric precursors has been successfully verified.