Infrasound in the ionosphere from earthquakes and typhoons

J. Chum, J. Y. Liu, K. Podolská, T. Šindelářová

研究成果: 雜誌貢獻期刊論文同行評審

25 引文 斯高帕斯(Scopus)

摘要

Infrasound waves are observed in the ionosphere relatively rarely, in contrast to atmospheric gravity waves. Infrasound waves excited by two distinguished sources as seismic waves from strong earthquakes (M > 7) and severe tropospheric weather systems (typhoons) are discussed and analyzed. Examples of observation by an international network of continuous Doppler sounders are presented. It is documented that the co-seismic infrasound is generated by vertical movement of the ground surface caused by seismic waves propagating at supersonic speeds. The coseismic infrasound propagates nearly vertically and has usually periods of several tens of seconds far away from the epicenter. However, in the vicinity of the epicenter (up to distance about 1000–1500 km), the large amplitudes might lead to nonlinear formation of N-shaped pulse in the upper atmosphere with much longer dominant period, e.g. around 2 min. The experimental observation is in good agreement with numerical modeling. The spectral content can also be nonlinearly changed at intermediate distances (around 3000–4000 km), though the N-shaped pulse is not obvious. Infrasound waves associated with seven typhoons that passed over Taiwan in 2014–2016 were investigated. The infrasound waves were observed at heights approximately from 200 to 300 km. Their spectra differed during the individual events and event from event and covered roughly the spectral range 3.5–20 mHz. The peak of spectral density was usually around 5 mHz. The observed spectra exhibited fine structures that likely resulted from modal resonances. The infrasound was recorded during several hours for strong events, especially for two typhoons in September 2016.

原文???core.languages.en_GB???
頁(從 - 到)72-82
頁數11
期刊Journal of Atmospheric and Solar-Terrestrial Physics
171
DOIs
出版狀態已出版 - 6月 2018

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