Tephra fall hazard and exposure analysis at corbetti volcanic system, Ethiopia: implications for risk management

Abstract The Corbetti volcanic system, located in the central part of the Main Ethiopian Rift, has no recorded eruptions in living memory but shows evidence of past activity ranging from highly explosive Plinian eruptions to dominantly effusive events. Approximately 1.1 million people live within 30 km of the volcano and over 12 million within 100 km, alongside critical infrastructure such as highways, Hawassa Airport, and major towns including Hawassa and Shashemene. A geothermal power plant is also under development within the caldera. Despite significant advances in understanding Corbetti through recent fieldwork, hazard assessment remains limited due to challenges in distinguishing deposits, poor lateral continuity, and scarce dateable material. This study combines new and existing field data with expert judgment to develop probabilistic tephra-fall footprints for four plausible eruption scenarios and a worst-case scenario. These are integrated with exposure data to assess potential impacts and eruption frequency. Results indicate an average recurrence interval of 520 years for any explosive eruption, with low-to-moderate volume events ten times more likely than large Plinian eruptions. Modelling shows tephra dispersal predominantly westward, potentially exposing over 750,000 people, ~3,400 km of roads, and ~1,600 km 2 of cropland to tephra loads exceeding 1 kg m − 2 (~1.6 mm) during a Plinian-type event. In the same scenario, more than 37,000 people could experience > 100 kg m − 2 (~16 cm) of tephra within 20 km of the vent. Even smaller eruptions could significantly impact agriculture and infrastructure, underscoring the need for preparedness and risk management in a region with no historical memory of explosive volcanism.