Identification of earthquake epicenter from measurements of electromagnetic pulses in the Earth

We have developed a system for finding arrival directions of electromagnetic (EM) pulses detected in the earth. The system detected an intense EM pulse just when an earthquake (M5.5) occurred. In the analysis of the detected EM pulse, we first derived its frequency dispersion characteristics. Using the data of the dispersion characteristics, we obtained frequency‐dependent arrival directions of the EM pulse. Among them, an exact direction pointing toward the EM pulse source was determined. Finally, we could find the source location of the EM pulse from the estimation of its propagation distance of a waveguide mode, which has shown that the EM pulse source location was on the earthquake epicenter.