A new ULF wave analysis for Seismo-Electromagnetics using CPMN/MAGDAS data

The Space Environment Research Center of Kyushu University has obtained geomagnetic data in the Circum-pan Pacific Magnetometer Network (CPMN) region for over 10 years, and has recently deployed a new real-time Magnetic Data Acquisition System (MAGDAS) in the CPMN region and an FM-CW radar network along the 210° magnetic meridian (MM) for space weather research and applications. This project intends to get the MAGDAS network fully operational and provide data for studies on space and lithosphere weather. In connection with this project, we propose a new ultra-low frequency (ULF) wave analysis method to study ULF anomalies associated with large earthquakes using magnetic data. From a case study of the 1999/05/12 Kushiro earthquake with magnitude M = 6.4, we found a peculiar increase of H-component power ratio AR/AM of Pc 3 magnetic pulsations a few weeks before the earthquake, where AR is the power obtained at Rikubetsu station (r = 61 km) near the epicenter and AM is the power obtained at a remote reference station, Moshiri (r = 205 km). It is also found that the H-component power ratio AD/AY of Pc 3 increased three times just a few weeks before the earthquake and after one week decreased to the normal level, where AD is one-day power at Rikubetsu station and AY is the one-year-average power.