Ionospheric perturbations observed due to Indonesian Earthquake (Mw=7.4) using GPS and VLF measurements at multi-stations

In the present paper Global Positioning System (GPS) as well as Very Low Frequency (VLF) measurements at multi-stations have been used to analyze ionospheric anomalies related with major earthquake (Mw = 7.4) of South West Banten (Lampung Area), Indonesia. The earthquake occurred on 02 August 2019 at 19:03:21 LT (epicenter at geog. lat = 07.22 degrees S, long. 104.83o E, depth 10 km). Tremors due to the earthquakes were felt in Jakarta, Bandung, and several parts of Java and Sumatra and more than 160,000 people were exposed and estimated release of energy to this earthquake (EQ) was 278 GWh. In this paper statistical analysis of the GPS-TEC data clearly supports the presence of earthquake signature in the form of anomalous perturbations in total electron content (TEC). Analysis found the presence of ionospheric perturbations 0-5 days before and after the main shock of the earthquake. The anomalous perturbations in the TEC were observed from few days to few hours prior to the main shock of the earthquake. Perturbations in TEC have been found to depend on the distance as well as direction of observation point from the epicentre. In general ionospheric perturbations after the EQ at all the stations are found larger than that before the EQ. VLF signal analysis using night-time fluctuation method indicates a significant increase in VLF amplitude before couple of days of EQ. Probable mechanisms behind these perturbations associated with EQ have also been discussed.