Investigation of the impact of a potential istanbul earthquake on the interceptor sewers of the küçüksu wastewater basin

Wastewater interceptor sewers, defined as the main wastewater collection systems within urban infrastructure, are large-diameter underground pipe networks that convey domestic, industrial, and similar wastewater generated in residential areas to treatment facilities. These systems generally operate based on gravity flow and are regarded as indispensable components of urban safety and environmental health. Earthquakes are ground motions caused by the sudden release of energy within the Earth's crust and represent one of the most destructive natural hazards affecting both the natural environment and human life. Particularly in metropolitan areas, earthquakes not only result in loss of life and property but also threaten the continuity of critical infrastructure systems, leading to severe disruptions in urban functionality. This situation necessitates a comprehensive evaluation of the vulnerability of infrastructure components to seismic hazards. Seismic effects such as ground displacements and deformations pose significant threats to the structural integrity of wastewater interceptor sewers, potentially causing joint separations, pipe cracking, and localized collapses. Such damages may lead to the uncontrolled leakage of wastewater into the environment and impair the operation of treatment facilities, thereby creating serious environmental and public health risks in the post-earthquake period. Within the scope of this study, the effects of a potential major earthquake in Istanbul on wastewater interceptor sewers were investigated. The Küçüksu Wastewater Basin, located on the Anatolian side of Istanbul, was selected as the study area, and eight international damage estimation methods were employed. These methods are PAHO/WHO, JICA, EIDINGER, O'ROURKE–DEYOE, YOO–KANG–KIM, ISOYAMA–ISHIDA–YUNE–SHIROZU, HAZUS, and ALA. The performance of these methods under seismic conditions was evaluated, and differences among the predicted damage levels and structural risks were comparatively analyzed. As a result of a scenario earthquake with a magnitude of approximately 7.5 affecting 17 wastewater interceptor sewers in the Küçüksu Wastewater Basin, the Ördekçi Interceptor was identified as the structure expected to experience the highest average damage ratio, with a value of 15.07%. In addition, damage ratios for the remaining 16 interceptors were estimated, providing results that may serve as a basis for planning strengthening and rehabilitation measures