Surface faulting vs built environment: lessons from the 2023 Mw 7.7 and 7.6 Turkey earthquakes

The February 6, 2023, twin earthquakes (Mw 7.7 and 7.6) hit Turkey and Syria regions. These seismic events were linked to the partial reactivation of the Eastern Anatolian Fault, producing surface faulting extending about 500 km. A multidisciplinary international team comprising geologists, engineers, and urban planners, conducted a comprehensive field survey between July 4–10, 2023 to assess the impact of fault proximity on the built environment. During the survey the group collected 334 fault records using both traditional structural geology methods and aerophotogrammetric surveys along with observations of near-fault structural damages and effects on structure crosscut by surface faulting. This study particularly focuses on the effects of surface faulting on structures and infrastructure, documenting damage to buildings, roads, and bridges. By linking damage patterns to fault characteristics, ground motion and structural features, it was possible to highlight vulnerabilities and sources of robustness of different cases observed. The analysis revealed significant variations in damage patterns, primarily influenced by the type of construction rather than the distance from the fault. For example, the interaction between foundation type and ground stiffness on the surface strongly influences the behavior of structural response and the resulting damage. When the strike-slip fault displacement involved the structure, compact shallow foundation showed the capacity to slide on the ground. The insights gained from this survey can enhance the consciousness of correct design choice in structures in seismically active areas, especially in case of possible surface faulting. By integrating geological observations with engineering assessments, this research contributes to a more comprehensive understanding of earthquake impacts and informs future near-fault mitigation strategies.