Positive and negative ionospheric disturbances prior to the 2016 christmas earthquake in Chile

Abstract

Global ionospheric maps (GIMs) provided by the Center for Orbit Determination in Europe (CODE) served to analyze ionospheric disturbances prior to the December 25, 2016 earthquake in Chile. Generating global two-dimensional differential vertical total electron content (VTEC) maps it was possible to detect three ionospheric disturbances. Eleven days (December 14, 2016) before the seismic event a positive ionospheric anomaly was detected. On the other hand, 8, 7 and 6 days prior to the earthquake, two negative ionospheric anomalies were also observed. All three anomalies were seen to fall inside the earthquake preparation region. Because during the days in which all three anomalies were observed, the geomagnetic and solar conditions were rather quiet and also the anomalies were localized, it can be suggested that they are seismo-ionospheric signatures due to the Chiloé earthquake. Moreover, it could be also indicated that the possible physical mechanism that originates these three anomalies is air ionization due to the emanation of radon from the Earth’s crust. It is very likely that for the negative ionospheric anomaly observed between December 18 and December 19, 2016, the fountain effect of the Equatorial Ionization Anomaly (EIA) plays a role as well in its generation.

Keywords

• ionospheric anomalies
• earthquakes
• vertical total electron content
• global ionospheric maps
• differential vertical total electron content maps