Alternative Approach for Tsunami Early Warning Indicated by Gravity Wave Effects on Ionosphere

The rapid displacement of the ocean floor during large earthquakes or volcanic eruptions causes propagation tsunami waves on surface ocean, and consequently internal gravity (IGWs) in atmosphere. IGWs pierce through troposphere into ionospheric layer. In addition to transferring energy ionosphere, they cause significant variations parameters, so have considerable effects radio this dispersive medium. study, double-frequency measurements Global Positioning System (GPS) ionosonde data were used determine disturbances irregularities response induced by 2011 Tohoku earthquake. critical frequency F2 layer (foF2) obtained from also showed clear that consistent with GPS observations. similar properties, detected about 25 min faster than ground stations at United States west coast, located 7900 km away tsunami’s epicenter. As a high vertical velocity, propagate obliquely atmosphere, can be for early warning. To further investigate spatial variation electron density (IED), profiles FORMOSAT-3/COSMIC (F3/C) satellites investigated both reference observation periods. During tsunami, reduction IED started 200 continued up 272 altitude. minimum observed was 2.68 × 105 el/cm3, which has happened 222 increased 767 altitude continuously, such maximum increase 3.77 el/cm3 355