Title: Study of anomalous VLF perturbations in possible relation to seismic activity.

Abstract

Anomalous perturbations of the ionosphere have been observed either as uctuations in the critical frequency of the F-region ionosphere, foF2, or as uctuations in the nighttime VLF signals that propagate through the Earth Ionosphere Waveguide. All anomalies appear from an earliest of three weeks to one day prior to an earthquake occurrence, hence leading to be used as possible presursors and aid in short term earthquake prediction. Earthquakes of magnitude 5.5 and greater have a signi cant chance of having associated ionospheric anomalies, and anomalies are only detected within a radius of 500km from the epicentre. Solar events, however, greatly a ect the ionosphere and make seismogenic ionospheric signals di cult to isolate. This study concentrates on anomalous VLF signal perturbations observed along the propagation path between the NWC transmitter in Australia and narrowband receivers in Budapest and Tihany, Hungary for July 2007 to February 2008. Comparisons of anomaly appearances and seismic activity occurring within the Dobrovolsky area to the propagation path were carried out, with anomalies being observed predominantly prior to major seismic events.