Evaluation of Total Electron Content before Large Earthquake

Earthquake is one of the bitterest and most destructive events that human life is endangered. Therefore, this natural disaster has preoccupied the minds of researchers and scientists in order to find clues before the earthquake and try to predict it. According to research performed one of the precursors of earthquakes, unusual changes in electron density before the occurrence of large earthquakes (greater than 6). Since Global Positioning System (GPS) data can be used to measure the ionospheric Total Electron Content (TEC), the technique has received attention as a potential tool to detect ionospheric perturbations related to earthquakes. Here, we analyze 2 data set from the Iran Permanent GPS Network (IPGN), a dense network of 122 continuous GPS stations on the Iran basin. This paper results show a TEC time series, majorly changes a few hours before the earthquake Ahar-Varzeqhan and a day before Saravan earthquake, which change is perceptible and may be useful for earthquakes forecasting. So TEC signals detect anomalous preceding earthquakes.