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GPS Observations of Ionospheric TEC Variations during 2015 Mw 7.8 Nepal Earthquake
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  • Monika Karki,
  • Ashok Silwal,
  • Narayan P. Chapagain,
  • Prakash Poudel,
  • Sujan Prasad Gautam,
  • Roshan Kumar Mishra,
  • Binod Adhikari,
  • Yenca Olivia Migoya Orue
Monika Karki
Amrit Campus, Tribhuvan University
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Ashok Silwal
Patan Multiple Campus, Tribhuvan University
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Narayan P. Chapagain
University of Illinois at Urbana Champaign
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Prakash Poudel
Patan Multiple Campus, Tribhuvan University
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Sujan Prasad Gautam
Central Department of Physics, Tribhuvan University
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Roshan Kumar Mishra
St. Xavier's College
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Binod Adhikari
St.Xavier's College, ,Maitighar

Corresponding Author:binod.adhi@gmail.com

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Yenca Olivia Migoya Orue
International Centre for Theoretical Physics
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Ionospheric total electron content (TEC) variations prior and after to the great Gorkha Earthquake in Nepal (Mw = 7.8) on April 25, 2015, were analysed using measurements from widely distributed Global Positioning System (GPS) network. This study has been performed to understand the relationship between ionospheric TEC anomalies and earthquake occurrences. The analysis of vertical TEC (VTEC) time series from different GPS stations shows that the abnormal TEC variations appeared few days up to a few hours before the events. The results indicate that deviation in VTEC observed on the distant GPS station from the epicentre was found less relative to that of the stations near the epicentre, inferring that the variation in ionospheric VTEC nearly inversely relies upon the distance of GPS stations from the epicentre. Moreover, the pre-earthquake ionospheric anomalies were also observed in the geomagnetically conjugated region. In view of the solar-terrestrial environment, the pre-earthquake ionospheric anomalies could be associated with the Nepal earthquake. The VTEC anomaly was identified when it crosses the upper bound or lower bound. The outcomes additionally show that TEC variation was dominant in the vicinity of the earthquake epicentre. We also describe contrast in TEC throughout the globe using global ionospheric maps at regular 2-hour UT intervals, the day before, during and after the earthquake. In addition, we observed that areas heavily influenced by TEC were found to be transposed from eastern sectors to western sectors through the equatorial plane.