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Abstract

The 2022 Tonga volcanic eruption at 04:14:45 UT on January 15^th created perturbations in the atmosphere and ionosphere on global scales. The pressure anomalies generated at Tonga almost revolved round the globe multiple times with noticeable amplitudes. Based on the released pressure, it may be understood that the pressure released in the eruption might have accumulated since long before the event. Therefore, in this work we attempt to study the available seismic, geodetic and atmospheric (Pressure, Total Electron Content) observations near Tonga region using data spanning over nearly 5 years to identify the long term and short-term precursory signatures, if any. Interestingly, our analysis indicates changes in the geodetic measurements nearly four years before the event. A clear phase change in the downward dipping GPS vertical displacement noticed near Tonga. In addition, the analysis also indicates some precursory signatures in the pressure variations recorded near Tonga just before the event. The precursory pressure anomalies above the station mean background variation spanning ~12 hours were observed nearly 36 hours before the main eruption. In addition to this, we have also noticed changes in the seismic background noise at the nearby broadband station well before the eruption consistent with the GPS observations. These long terms and short-term changes noticed in the study indicate the changes in the subsurface during the preparation phase of the eruption. Further, we are working to model the observed changes and associated physical mechanism.