Natural hazards, particularly earthquakes, can trigger technological accidents in industrial facilities, known as Natech events, leading to cascading secondary hazards. This paper focuses on Istanbul, a densely populated megacity situated in a high seismic activity zone. Past devastating earthquakes in Türkiye, such as Kocaeli (1999) and Kahramanmaraş (2023), have demonstrated the potential for catastrophic Natech events. This study presents neighborhood-level assessment of potential Natech risks in Istanbul specifically under the scenario of the probable earthquake, analyzing the spatial intersection of structural vulnerability and hazardous industrial/economic activities. The methodology integrates seismic structural damage estimations for 939 neighborhoods using geocoded data on over 500,000 businesses, based on workplace hazard classification. Three indices were introduced: ( i ) Damage Ratio Index to quantify seismic structural risk per neighborhood, ( ii ) Natech Share Index to assess the share of very hazardous business activities, and Integrated Natech-Risk Assessment to combine structural risk and Natech-risk. The analysis identifies 8,785 businesses engaged in activities posing significant Natech risks, 4,843 chemical leakage and 3,942 fire/explosion. Findings indicated that neighborhoods classified with high structural vulnerability combined with a high share of hazardous activities represent critical hotspots, with approximately 17% of Istanbul’s neighborhoods falling into the highest risk category, encompassing 31% of the city’s population, 25% of the total businesses and 24% of the Natech-risky businesses. These findings highlight the critical necessity of integrating seismic hazard assessments with industrial risk management and targeted land-use planning to enhance urban resilience and mitigate potentially devastating consequences from Natech events triggered by the seismic events.

Resilience in the face of crises is crucial for minimizing the impact of disasters and enabling rapid recovery. This study delves into the interlinked consequences of two seismic events that significantly impacted Türkiye in 1999 and 2023. Using an impact chain analysis, the aim is to provide a thorough understanding of the extensive effects on structures, infrastructure, and socio-economic dynamics. The research also examines the evolution of disaster management practices from the 1999 Kocaeli Earthquake to the more recent seismic events in 2023, highlighting advancements in risk management and resilience. Structurally, both seismic events revealed vulnerabilities in building design, emphasizing seismic shortcomings that led to widespread damage. Earthquakes exert a profound impact on critical infrastructure, affecting transportation, communication, and energy systems, with cascading effects that extend to the broader socio-economic landscape. The effectiveness of the methodology, particularly, the Impact Chain analysis, is emphasized as it reveals complex causal relationships. Visual representations support effective communication and collaboration among stakeholders, offering a holistic perspective on systemic risks. In conclusion, this study contributes to understanding disaster resilience and provides a foundation for subsequent research, policy formulation, and pragmatic strategies for disaster preparedness and response.