Ionospheric Precursors to Earthquakes: A Preliminary Analysis of the JoF2 Critical Frequencies at Chung-Li Ground-Based Station for Vertical Sounding of the Ionosphere (Taiwan Island)

Ahstract-A preliminary statistic analysis of the fon critical frequencies measured at Chung-Li (Taiwan Island) ground-based station for vertical sounding of the ionosphere is performed in order to reveal ionospheric precursors to earthquakes. A specific pattern of ionospheric anomalies (possible precursors to earthquakes) is revealed for deep-focus earthquakes of a region where hypocenter is at a depth of 60-300 km.