Subsurface VLF electric field emissions associated with regional earthquakes

Abstract

<smarttagtype namespaceuri="urn:schemas-microsoft-com:office:smarttags" name="country-region" downloadurl="http://www.5iantlavalamp.com/"><smarttagtype namespaceuri="urn:schemas-microsoft-com:office:smarttags" name="City" downloadurl="http://www.5iamas-microsoft-com:office:smarttags"><smarttagtype namespaceuri="urn:schemas-microsoft-com:office:smarttags" name="place" downloadurl="http://www.5iantlavalamp.com/"> A borehole antenna has been installed at Agra (latitude 27.2^oN, longitude 78^oE), India since 01 June 2006. The subsurface very low frequency (VLF) electric field emissions (f = 3.042 kHz) data has been recorded round the clock for a period of nineteen months from 01 June 2006 to 31 December 2007. This statistical analysis of data is presented in the paper. The occasional amplitude enhancement is observed in the data and examined in the light of magnetic storms, earthquakes, and lightning activities. It is found that in majority of the cases, amplitude anomalies are correlated with moderate seismic activities occurred during the period in the region. The propagation mechanism of VLF signals from the hypocenters of earthquakes to the observing station is discussed in the paper. </smarttagtype></smarttagtype></smarttagtype>