Observation evidences of atmospheric Gravity Waves induced by seismic activity from analysis of subionospheric LF signal spectra

• Published in: Natural Hazards and Earth System Sciences
• Main Authors: Rozhnoi, A., Solovieva, M., Molchanov, O., Biagi, P.-F., Hayakawa, M.
• Format: Text
• Language: English
• Published: 2018
• Subjects: Petropavlovsk; Petropavlovsk-Kamchatsky; Kamchatka
• Online Access: https://doi.org/10.5194/nhess-7-625-2007; https://nhess.copernicus.org/articles/7/625/2007/

We analyze variations of the LF subionospheric signal amplitude and phase from JJY transmitter in Japan (F=40 kHz) received in Petropavlovsk-Kamchatsky station during seismically quiet and active periods including also periods of magnetic storms. After 20 s averaging, the frequency range of the analysis is 0.28–15 mHz that corresponds to the period range from 1 to 60 min. Changes in spectra of the LF signal perturbations are found several days before and after three large earthquakes, which happened in November 2004 (M=7.1), August 2005 (M=7.2) and November 2006 (M=8.2) inside the Fresnel zone of the Japan-Kamchatka wavepath. Comparing the perturbed and background spectra we have found the evident increase in spectral range 10–25 min that is in the compliance with theoretical estimations on lithosphere-ionosphere coupling by the Atmospheric Gravity Waves (T>6 min). Similar changes are not found for the periods of magnetic storms.