On 6 February 2023, near Kahramanmaraş in south-central Türkiye, an event underscored the vulnerability of cities to seismic activity, revealing a lack of preparedness for substantial shocks. The contributing factors are manifold, yet fundamentally, the collapse of buildings and infrastructure can be attributed to an underestimated capacity for meticulous settlement planning (location) and the adoption of advanced techniques for resilient construction (structure). Regrettably, as has been investigated by many research works, ordinary urban planning in Türkiye hardly finds ways to integrate the vulnerability analysis for settlement expansion, which includes the full integration of geological characteristics with the analysis of building sensitivity. With this work, we wanted to build a composite risk index based on earthquake vulnerability, hazard amplification map, and exposure. We designed the composite index in Izmir’s basin, Türkiye’s third most populated city, to answer the question: What if a destructive earthquake strikes this densely settled area? The results illustrates how the coupled integration of digital data on geology with settlements and infrastructure in a Geographic Information System environment can be used to produce risk maps and plan the anthropic system’s adaptation carefully. Findings demonstrate the city is highly vulnerable to earthquakes and identify priority areas for planning intervention, relocation, and renovation of buildings.