Combined effects of Geomagnetic storm and regional Earthquake on low latitude VLF radio signals: A case Study

Anomalous behavior of Very Low Frequency (VLF) radio signals from the VTX (18.2 kHz) and NWC (19.8 kHz) transmitters during geomagnetic storm, followed by a moderate size earthquake, are analyzed and presented in this paper. There was Geomagnetic storm on 10
^th
and 11
^th
September, 2018 and a moderate size isolated earthquake on 12
^th
September, 2018. Using standard deviation method, night time VLF amplitude of both the propagation path are found to deviate beyond -3sigma level on 10th September coinciding with the occurrence of geomagnetic storm. Pre-seismic and post-seismic signal anomalies are also identified in both propagation paths linked with the earthquake of 12th september 2018.