Investigating ground deformation and SO2 emissions of the November 2020 Ili Lewotolo Eruption (Indonesia) using NSBAS InSAR and Sentinel-5P

Ili Lewotolo Volcano, a stratovolcano in East Nusa Tenggara, Indonesia, erupted on November 27, 2020, following eight years of dormancy, releasing significant ash and sulfur dioxide (SO₂) emissions. This study is the first to combine multi-temporal Interferometric Synthetic Aperture Radar (InSAR) and SO₂ imaging for monitoring volcanic activity, offering a comprehensive pre- and post-eruption analysis approach. The New Small Baseline Subset (NSBAS)-InSAR method, using Sentinel-1 SAR data (from November 2019 to November 2020), detected notable ground deformation, while the Tropospheric Monitoring Instrument (TROPOMI) sensor on Sentinel-5P (from January 2020 to December 2021) captured fluctuations in SO₂ emissions. InSAR time-series analysis revealed significant ground uplift, indicating a magma source around 2000 m depth, confirmed through parametric optimization using the Mogi model. Furthermore, SO₂ levels surged by 512 % during the eruption compared to pre- and post-eruption periods, demonstrating a clear correlation between ground deformation and gas emissions. This combined approach provides deeper insights into volcanic behaviour and underscores the value of combining remote sensing techniques to enhance hazard mitigation strategies, paving the way for an effective early warning system for monitoring volcanic activity. • First study combining NSBAS InSAR & Sentinel-5P for Ili Lewotolo volcano dynamics, showing potential for global application. • NSBAS InSAR shows a 35 mm/ year ground deformation produced by over-pressurized magma at around 2000 m depth. • SO2 emissions peaked at 1.4 DU post-eruption, declining below 0.4 DU by 2021's end.