Investigations of Anomalous Spiky Variations in VLF Electromagnetic Signals Associated with Western Mediterranean Sea Earthquake

Abstract

In the present work electromagnetic signals have been critically examined to delineate their correlation with Western Mediterranean Sea Earthquake occurred on July 07, 2011 (M=5.3). Anomalous variations in electromagnetic signals in VLF range may be considered as most promising tools for short term Earthquake precursor. To investigate the precursors of Earthquake, VLF signal observed by Sudden Ionospheric Disturbances (SID) monitoring station are used and it was found that the amplitude and number of spikes of VLF signals are increased anomalously on June 21 and June 29 before the preceding Earthquake. Another peak was also observed on July 12, 2011 which may be consider as post seismic activity for these signals. The variations in VLF electromagnetic signals prior to seismic activity may be produced by an electromagnetic instability process in the Earth`s atmosphere up to the ionosphere triggered by charged aerosols or electromagnetic waves induced in the preparatory stage of shallow (Depth≤55 km) Earthquakes.