Possible Earthquake Precursors Observed in Geomagnetic Variations in the East Coast of Honshu, Japan

The application of electromagnetic signals in earthquake study has been demonstrated by previous researchers by monitoring the geomagnetic variations. This prospective study sought to enhance the reliability of earthquake forecasting, by extending the study to a non-seismological area since the previous studies were mainly focused more in the seismological area. A case-study approach was conducted in this study by utilizing the diurnal variation range ratio (DVRR) method. Five earthquake events that occurred between January 2005 and December 2016 in the vicinity of the east coast of Honshu, Japan were observed. The anomalies were detected as early as 60 days to 1 day prior to the earthquake events. All geomagnetic N, E, and Z-components showed anomalous behavior during the quiet days but with temporal lags between the components. It can be concluded that the anomalies were not related to global geomagnetic disturbances and might be associated with the respective earthquake events. The diurnal range of geomagnetic variations were also influenced by the focal mechanism since the events with reversed faulting showed increasing geomagnetic variations, meanwhile only one event with normal faulting shows the mixture of increase and decrease of geomagnetic variations diurnal range prior to the earthquakes. Future studies will be conducted to correlate with seismo-ionospheric response and physical ground movement prior to the events.