[SEM21-P08] Electromagnetic field fluctuations recorded in MT data during the eruption of Kirishima Shinmoe-dake in 2018
Keywords:electromagnetic signal, explosive eruption, infrasound, seismic motions, Shinmoe-dake
Twenty eruptions during March to June 2018 were selected for an analysis. We use the MT data recorded at two sites ((1) 5.1 km NW of the Shinmoe-dake crater, and (2) 3.2 km WSW of the Shinmoe-dake crater) and a seismic and infrasound observations data recorded at 30 m away from (1) MT site. We obtained MT time series data with physical unit (mV/km, nT) by applying a Fourier transform, incorporating the frequency responses of instruments and inverse Fourier transform. We also got time series data of physical units (μm/s, Pa) from seismic and infrasound data.
At (1) MT sites, the electromagnetic signals of explosive eruptions well synchronized with the seismic vertical motions and infrasound data. The shape of the impulsive compression phase of infrasound data looks very similar to the shape of EM variation at that time. We also concludes that the EM signals are not occurred in the crater but occurred at the area very close to the MT observation sites.
We will carefully investigate the relationship between electromagnetic signals and seismic and infrasound data close to the Shinmoe-dake volcano and discuss why the seismic and infrasound generates electromagnetic variations.