Preseismic ionospheric anomalies detected before the 2016 Kumamoto earthquake

Abstract

AbstractOn 15 April 2016, the Kumamoto earthquake (Mw 7.3) occurred in Japan with no warning signals. Global Navigation Satellite System (GNSS) receivers provide useful information on disturbances in the ionosphere by calculating the changes in total electron content (TEC), which is the number of electrons in the ionosphere. Here we show our recently proposed correlation analysis of TEC data which can detect the preseismic ionospheric anomalies from the public GNSS data. Our method detected the ionospheric anomaly several tens of minutes before the 2016 Kumamoto earthquake near its epicenter. Furthermore, we gave an indicator to distinguish between the preseismic TEC anomalies and the medium‐scale traveling ionospheric disturbances (MSTIDs) by calculating the anomalous area rates. These results support the hypothesis for existence of the preceding phenomena before large earthquakes.