Ionospheric anomalies detected by GPS TEC measurements during the 15 August 2007 Peru earthquake

A strong earthquake of magnitude 8 occurred near the coast of Peru at 23:40:58 UT on 15 August 2007. Its epicenter was located at geographic latitude 13.386°S and longitude 76.603°W with depth of about 39 km. In this paper the seismogenic variations in the equatorial and low-latitude ionosphere have been examined during July-August 2007 around the time of the Peru earthquake. The Global Ionospheric Maps (GIMs) of total electron content (TEC) provided by the International GNSS Service (IGS) network have been utilized. The upper and lower bound of inter-quartile range (IQR) are constructed to monitor the abnormal variations in TEC other than the diurnal and day-to-day pattern. Anomalous TEC variations at the low-latitude regions in the vicinity of the epicenter were observed 35 days before and 8 days after the main shock. Usually the zone of the anomaly maximum manifestation had spatial scale of more than 1000 km in longitude and latitude. The solar activity and geomagnetic conditions were quiet during the period under investigation. Therefore, the observed anomalous ionospheric variations are likely to be associated with the Peru earthquake.