Ionospheric disturbances (infrasound waves) over the Czech Republic excited by the 2011 Tohoku earthquake

0379768 - ÚFA 2013 RIV US eng J - Journal Article
Chum, Jaroslav - Hruška, František - Zedník, Jan - Laštovička, Jan
Ionospheric disturbances (infrasound waves) over the Czech Republic excited by the 2011 Tohoku earthquake.
Journal of Geophysical Research. Roč. 117, A8 (2012), A08319/1-A08319/13. ISSN 0148-0227
R&D Projects: GA ČR GA205/09/1253; GA ČR(CZ) GAP209/12/2440; GA MŠMT LM2010008
Institutional support: RVO:68378289 ; RVO:67985530
Keywords : Infrasound excited by seismic waves is observed in the ionosphere * Observation is about 9000 km from the epicenter * High cross-correlation, and Doppler shift measurements are presented
Subject RIV: BL - Plasma and Gas Discharge Physics; DE - Earth Magnetism, Geodesy, Geography (GFU-E)
Impact factor: 3.174, year: 2012
http://onlinelibrary.wiley.com/doi/10.1029/2012JA017767/abstract

A train of large amplitude infrasound wave packets was observed by multipoint Continuous Doppler sounding system in the ionosphere over the Czech Republic on 11 March 2011. It is shown that these infrasound wave packets originated from vertical motion of the ground surface that was caused by arrival of seismic waves generated by the strong Tohoku earthquake. The infrasound wave packets were observed in the ionosphere at heights of ~210–220 km about 9 min after the detection of corresponding wave packets on the ground, which is consistent with the calculated time for vertically propagating infrasound waves. Absolute values of cross-correlation coefficients between ionospheric and ground measurements are typically higher than 0.9 (for two wave packets ~0.98). The individual wave packets recorded on the ground have different observed horizontal velocities and correspond to different types of seismic waves. A comparison of vertical velocities of ground motion with oscillation velocities of air particles in the ionosphere indicates that almost 1/10 of the infrasound energy flux excited at the ground reached the altitudes of ~210–220 km for wave periods longer than ~30 s. Estimates of sound attenuation are performed. It is also shown that it is necessary to consider the value of electron density gradient at the reflection height of the sounding radio wave, and air (plasma) compression owing to the infrasound wave to get reasonable estimates of oscillation velocities of air particles from Doppler shift frequencies.
Permanent Link: http://hdl.handle.net/11104/0210650