Analysis of ionospheric disturbances due to earthquakes using 3D tomography models to test the height maximum of CID correlation in various regions

Ionospheric disturbances caused by acoustic waves emitted during earthquakes were studied using the Global Navigation Satellite System (GNSS) to analyze the changes in total electron content (TEC) values. GNSS signals normally propagate from satellites to receivers through the ionosphere layer. The delayed signals can be used to obtain TEC values by passing through the layer. Therefore, this study aims to analyze Coseismic Ionospheric Disturbances (CIDs) in six earthquakes, including 2016 M 7.8 New Zealand (about 0.49 TECU), 2018 M 7.9 Alaska (about 0.20 TECU), 2005 M 7.2 California (about 0.29 TECU), 2023 M 7.5 Turkey (about 0.49 TECU), 2012 M 8.6 Sumatra (about 2.98 TECU), and 2012 M 8.2 Sumatra (about 1.49 TECU) earthquakes. The propagation speed of the wave from the earthquake epicenter, identified as an acoustic wave, was estimated to be between 0.6 and 1.0 km/s. The 3D tomography modeling was performed to analyze the TEC height variations in the ionosphere to obtain a more accurate spatial analysis of TEC due to earthquakes. Moreover, checkerboard accuracy tests were applied to test the resolution of the 3D tomography model. The maximum ionization correlation test was also conducted for the six earthquakes to determine variations in the maximum ionization height of the ionosphere. The correlation test results between magnitude and maximum CID height produced a moderate correlation. The greater the earthquake magnitude, the higher the maximum CID detected. This is because greater earthquake produces compressed energy, which reduces the ionospheric density and reaches the maximum height. In addition, the maximum CID height is higher at night than in the afternoon because the E layer disappears at night.