Abstract
In this paper, we analyze the TEC data for April 2013 observed at Agra station, India (geogr. lat. 27.2° N, long. 78° E) to examine the effect of earthquake of magnitude M = 7.8 which occurred on 16 April 2013 at Pakistan–Iran border region. We process the TEC data using the s statistical criterion to find out anomalous variation in TEC data. We also study the VLF propagation signal from NPM, Hawaii (21.42° N, 158° W), which is monitored at the same station (Agra station) in the light of this earthquake as well as solar flares. The nighttime fluctuation method is used to analyze the VLF data for the period of ±5 days from the day of earthquake (11–21 April 2013). The anomalous enhancements and depletions are found in TEC data on 1–9 days before the occurrence of event.
Highlights
Various techniques for possible earthquake prediction have been found and used, in which the one based on ionospheric measurements has found widespread attention and importance
Liu et al (2001) have carried out both the foF2 measurements using Chug-Li ground based ionosonde and global positioning satellites (GPS) based total electron content (GPS-TEC) measurements corresponding to Chi-Chi earthquake (M = 7.7) in Taiwan and found 1-4 days of ionospheric precursors
We need to explain the exact reason of anomalous variation using the coupling mechanisms between the lithosphere, atmosphere, and ionosphere, involving atmospheric gravity waves, and the vertical electric fields generated during the earthquake preparation periods, as suggested by earlier workers (Hayakawa and Fujinawa 1994, Hayakawa 1999, Hayakawa and Molchanov 2002, Pulinets 2004, 2009)
Summary
Various techniques for possible earthquake prediction have been found and used, in which the one based on ionospheric measurements has found widespread attention and importance. Liu et al (2001) have carried out both the foF2 measurements using Chug-Li ground based ionosonde and GPS based total electron content (GPS-TEC) measurements corresponding to Chi-Chi earthquake (M = 7.7) in Taiwan and found 1-4 days of ionospheric precursors. Liu et al (2004a) have examined the effect of 20 earthquakes (M 6.0) occurred in Taiwan area between 1999 to 2002 on the variation of TEC and found 1-5 day precursory period. Recent studies based on consideration of large number of earthquakes over extended period of time and their influence on the variation of GPS-TEC have been carried out by Liu et al (2009) and Akhoondzadeh et al (2012). Pundhir et al (2014) have studied the effect of multiple earthquakes on GPS-TEC data and found the precursors on 1-9 days before the occurrence of main shock
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