Analysis of Ionospheric perturbation and pre-estimation of epicenter of the recent earthquakes using Global Anomaly Map

The total electron content (TEC) of the ionosphere over the epicenter regions for the earthquakes of El Salvador and Peru of 2016 were analyzed for a period of 15 days prior to event using median, upper and lower bounds (defined by standard deviations). The sudden fluctuations leading to negative anomalies of TEC variation before 7–12 days of the events were observed. These anomalies/perturbations were attributed to seismogenic causes as the solar and geomagnetic contributions to TEC variation in ionosphere were negligible during the considered time period. In order to assess the TEC variations in spatial domain during the period prior to earthquake, major plate boundaries were also considered along with TEC gradient and global ionospheric anomaly maps in 2-D along with the epicenters, which showed very promising correlation. Therefore, 2-D anomaly maps, spatial variation of the TEC conjugates, gradients of the TEC and nearest plate boundaries were considered to determine the probable epicenters, which were found to be within 150–160 km from the actual epicenters reported by USGS.