Land Subsidence Hazard and Building Collapse Risk in the Coastal City of Lagos, West Africa.

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Every year incidents of building collapse claim many lives and cause enormous financial losses around the world, which are often blamed on low-quality materials, non-compliance with standards, lack of oversight, and failure to enforce building codes. Here, we highlight the role of land subsidence in triggering unprecedented collapses in the city of Lagos, Nigeria, which has reported over 200 casualties during 152 building failures since 2005. We used acquisitions from radar satellites for 2018-2021 and provided data that link subsidence to foundation damage and high building failure risk in the region. We estimate that an area of 5-81km2 and 255-4,000 buildings are exposed to a high to very high risk of collapse for short-term (10years) to long-term (75years) periods. Differential land subsidence can trigger building collapse, and the data presented here will enable authorities to create adequate building codes and standards and devise mitigation strategies.