Anomalous VLF electric field perturbations associated with Chamoli earthquakes of March/April 1999

Employing borehole and terrestrial antennas, Very Low Frequency (VLF) electric field perturbations associated with Chamoli earthquakes which occurred in the months of March and April 1999 have been monitored at our Agra station (geographic lat. 27.8°N, long. 78°E). The results show that electric fie...

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Bibliographic Details
Published in:Current science (Bangalore) 2001-06, Vol.80 (11), p.1416-1421
Main Authors: Singh, Raj Pal, Mishra, P. K., Singh, Birbal
Format: Article
Language:English
Subjects:
Antennas
Astronomical magnitude
Earthquakes
Electric fields
Electromagnetic noise
Electromagnetism
Lightning
Noise reduction
RESEARCH COMMUNICATIONS
Signal noise
Waveforms
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Summary:Employing borehole and terrestrial antennas, Very Low Frequency (VLF) electric field perturbations associated with Chamoli earthquakes which occurred in the months of March and April 1999 have been monitored at our Agra station (geographic lat. 27.8°N, long. 78°E). The results show that electric field perturbations started appearing in the form of noise bursts 16 days prior to the occurrence of the main shock on 29 March 1999. In majority of the cases of the noise bursts the effect was observed by borehole antenna only, indicating that the signal propagated through crustal region. This result is interpreted in terms of propagation of signals through conductive channels along Delhi–Haridwar ridge and parallel to them between the source and the observing station.
ISSN:0011-3891