Some ionospheric responses to earthquakes

Since 2010 long term observations by ionosonde in Kazan with 1-min intervals is made. Such operating mode allows rare effects occurring in ionosphere and caused by earthquakes and big explosions would be record in ionogram. In paper the characteristic features (signature) of severe events are detected in ionograms when the epicenter was at a great distance. The revealed signatures are a F1 layering, appearance of a trace focusing and a particular TID in ionograms. The duration of these events is defined and calculations of speed of wave disturbances is made.