GNSS ionospheric seismology: Recent observation evidences and characteristics

The detail and nature of earthquakes are still challenging from traditional technique observations, e.g., seismometers and strong motion accelerographs. Nowadays, the ionospheric total electron content (TEC) can be obtained from ground-based global navigation satellite systems (GNSS) and space-borne GNSS Radio Occultation, which can be used to investigate the seismo-ionospheric disturbances and may provide insights on the earthquake. In this paper, GNSS ionospheric seismology is presented and reviewed, including methods, observation results and characteristics. Case studies of the 2008 Wenchuan earthquake and 2011 Japan earthquake are presented using ground-based GNSS observations. Significant co-/post-seismic ionospheric anomalies are found from continuous GNSS observations near the epicenters, showing that the seismic ionospheric total electron content (TEC) disturbances were derived mainly from the main shock. The detailed pattern and evolution of the ionospheric disturbance are revealed by denser GNSS observations. Some simulations explore the nature of the ionospheric perturbation, highlighting that acoustic-gravity waves are generated close to the epicenter, and that surface Rayleigh waves and tsunamis generate in the atmosphere/ionosphere acoustic and gravity waves respectively. These waves are induced by solid-Earth/ocean and atmosphere coupling at the ground or ocean interface with the atmosphere propagating upward until the ionosphere create strong perturbation in plasma density and plasma velocity.