A study of some research work on soil radon concentration and ionospheric total electron content as earthquake precursors

This review discusses some research on two earthquake precursors—soil radon concentration, a geochemical precursor; and Total Electron Content (TEC), an atmospheric one, studied in some earthquake-prone regions in the world. These two precursors were chosen because their generation mechanisms are interlinked. The selected soil radon studies focused on establishing anomalous radon fluctuations as a robust precursory signal for medium to high-magnitude earthquakes, including determination and removal of meteorological effects from soil radon time series, and identification of genuine pre-seismic anomalies. For the seismic precursory property of TEC, studies on detecting seismogenic TEC fluctuations and their formation mechanisms were discussed.