Investigation of the relation between the earthquake and the ionospheric total electron content

Earth?s ionosphere is a dominant factor in space weather and the variability of the ionosphere is important for the ionospheric physics and radio communications. The characterizing property of the ionosphere is the electron density distribution that shows variation as a function of height, latitude, longitude, geomagnetic activity, solar and seismic activity. An important measurable quantity about the electron density is the Total Electron Content (TEC) which is proportional to the total number of electrons on a line crossing the atmosphere. TEC measurements enable monitoring variations in the space weather. Global Positioning System (GPS) and the network of world-wide receivers provide a cost-effective solution in estimating TEC over a significant proportion of global land mass. In this study, TEC obtained for eight GPS stations located in Japan and China and eleven TUSAGA-Active GPS stations located in Turkey are compared with each other using the Cross Correlation Coefficient (CIK), symmetric Kullback-Leibler Distance (KLD), L2-Norm (L2N), sliding window statistical analysis and Divergence of Distributions (DI) and Difference of Distributions (DF) for quiet days of the ionosphere, during severe geomagnetic storms, and strong earthquakes. It is observed that only KLD and L2N can differentiate the seismic activity from the geomagnetic disturbance and quiet ionosphere if the stations are in a radius of 340 km. When TEC for each station is compared with an average quiet day TEC for all periods using CIK, KLD and L2N, it is observed that, again, only KLD and L2N can distinguish the approaching seismicity for stations that are within 150 km radius to the epicenter. When the TEC of consecutive days for each station and for all periods are compared, it is observed that CIK, KLD and L2N are all successful in distinguishing the geomagnetic disturbances. Using sliding window statistical analysis, moving averages of daily TEC with estimated variance bounds are also obtained for all stations and for all days of interest. When these bounds compared with each other for all periods, it is observed that all CIK, KLD and L2N are successful tools for detecting ionospheric disturbances.