Investigation of geomagnetic data as a precursor of 5 Sep. 2018 Japan earthquake (Mw=6.6)

Magnetic anomalies before an earthquake occurrence have long been discussed as precursors to seismic activity. In this study, by repeatedly over-plotting magnetic data related to each day (24 hours) in the same frame, for different components (Z, Y, X) or (Z, D, H) of three geomagnetic stations in Japan (MMB, KAK, KNY) over a period of one year, the characteristic curve of the geomagnetic stations are extracted. The purpose of this method is to try to reduce the effect of diurnal variations in the magnetic field from geomagnetic records and its use led to a more significant differentiation of the anomalies observed before the earthquake compared to the original data. Although previous studies have shown that geomagnetic data can be used as a precursor of earthquakes, the presence of magnetic storms in the study period led to the conclusion that commenting on the relationship between the observed anomalies and the earthquake requires more data and investigations.