Investigation on the reliability of earthquake prediction based on ionospheric electron content variation

Abstract

Ionosphere region of Earth’s upper atmosphere ranging from 90 km to 1000 km altitude, has a significant effect on military and civilian communications, satellite communications and positioning systems. Solar, geomagnetic, gravitational and seismic activities cause variations in the electron distribution of the atmosphere. The number of electrons within a vertical column of 1 m2 cross section, which is called as Total Electron Content (TEC), is a measurable feature of the ionosphere that provides valuable information about the ionosphere. TEC can be measured fast and accurately by using the phase difference between transmitted satellite positioning signals such as in the Global Positioning System (GPS). To investigate the reliability of earthquake prediction based on detection of local ionospheric anomalies, TEC measurements obtained from a network of GPS receivers over a period of 2 years in 2010 and 2011 are used to generate detection signals. For a day of interest, after selecting a receiver station surrounding GPS stations that are located within 150 km of the chosen station used to estimate TEC measurements at the chosen station. In one of the proposed techniques, detection of ionospheric anomalies is based on distance between measured TEC and its estimate. Detection threshold is obtained based on statistical variation of this distance for the days with insignificant seismic activities. Also, another detection technique based on temporal variation of TEC measurements is proposed. Both individual and fused detection performances of these techniques are investigated for a given level of false alarms. It is observed that the fused detection has superior performance and able to detect 15 out of 23 earthquakes of magnitude larger than 5 in Richter scale while generating 8 false alarms.