Detection of Atmospheric Gravity Wave Activity during several Earthquakes

摘要

The coupling between seismic hazards and ionosphere is an important topic in research field. The perturbation in ionosphere due to earthquake is an example of seismo-ionospheric coupling. The perturbation can be analyzed through the various channels of a mechanism called Lithosphere-Atmosphere-Ionosphere Coupling (LAIC). The three channels are thermal, electromagnetic and acoustic channel. Atmospheric Gravity wave (AGW) is lie in the acoustic channel. AGW is the most reliable parameter to predict the ionospheric perturbation due to Earthquake. In this study, we compute the potential energy (Ep) associated with the gravity waves. The Ep is derived from using temperature profiles retrieved from observations of Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument on board the Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED)satellite for Tohoku Earthquake (Japan) (11 March 2011, MW - 9.0), Nepal Earthquake (25 April 2015 and 12 May 2015, MW - 7.8, MW - 7.3), Kumamoto Earthquake (15 April 2016, MW - 7.0) and Pakisan Earthquake (24 September 2019, MW - 5.6). There is a significant increment in AGW activity just before all the earthqukes. the abnormal AGW activity in the stratosphere is detected before the earthquake, and the coincidence of stratospheric AGW activity with VLF sub-ionospheric perturbations provides further support to the AGW hypothesis of the LAIC process.