Abstract The assessment of volcanic hazards is crucial to develop effective emergency plans, especially for volcanoes close to urban areas or under air traffic routes. Impact assessment for expected scenarios relies on underlying numerical models that require eruption source parameters as inputs, and forecasts drastically depend on their robust reconstruction during ongoing events. We apply a novel tephra deposit inversion workflow built on ensemble methods and data assimilation techniques to reconstruct the explosive events that occurred at Mt Etna, Italy, between 3 and 5 December 2015. Based on results from previous studies, we reconstruct this eruption using the Gaussian with Non‐negative Constraints data assimilation method. Results agree well with independent observations and highlight the potential for automatized procedures in volcanic hazard assessment.