Ionospheric perturbations caused by some major earthquakes in India

• Published in: Physics and chemistry of the earth. Parts A/B/C 2004, Vol.29 (4), p.537-550
• Main Authors: Singh, Birbal, Kushwah, Vinod, Singh, O.P., Lakshmi, D.R., Reddy, B.M.
• Format: Article
• Language: English
• ISSN: 1474-7065; 1873-5193
• DOI: 10.1016/j.pce.2003.12.007

The effects of six major earthquakes that occurred in India during the last 13 years between 1988 and 2001 at locations of Bihar-Nepal border, Uttarkashi, Latur, Jabalpur, Chamoli, and Bhuj are examined on the nighttime (18.00–06.00 h LT) ionospheric parameter f 0 F 2 by employing the digital ionosonde data obtained from Ahmedabad (Geographic latitude 23.01°N, longitude 72.36°E). The percent deviations of f 0 F 2 from monthly median are determined for pre-midnight (18.00–00.00 h LT) and post-midnight (00.00–06.00 h LT) sectors and then three days running mean for the peak reduction in percent deviation in the two time sectors are examined critically. The results show that f 0 F 2 are reduced in both the time sectors prior to the occurrence of main shocks. In pre-midnight sector the reduction is between 24% and 35%, 0–4 days before the main shocks and in the post-midnight sector it is between 18% and 30%, 1–15 days before the main shocks. The statistical analysis carried out by using mean and standard deviations from 10 years of data for 24 h periods shows morning, evening, and late evening reductions in all but one case. The effects of magnetic storms in reducing the f 0 F 2 are identified clearly and they do not vitiate the effects of earthquakes.