Holistic analysis of liquefaction risks and land subsidence for building areas located in active fault zones

In active fault zones, land subsidence and surface liquefaction are potential hazards that can seriously threaten urban infrastructure and, consequently, human life. Following the devastating 1999 Marmara Earthquake, newly established organized industrial zones led to a rapid increase in population, construction, and building density in the eastern Marmara region, particularly centered around the İzmit district of Kocaeli Province, Türkiye. The rapid urbanization observed along the North Anatolian Fault Zone and in alluvial areas with low soil stability has exposed urban areas to compounded geohazard risks such as earthquakes, liquefaction, and land subsidence. In this study, spatio-temporal vertical surface deformations along the eastern Marmara segment of the North Anatolian Fault were detected using the advanced Small Baseline Subset (SBAS) InSAR technique, based on both ascending and descending mode Sentinel-1A SAR data between 2014 and 2020. In liquefaction studies, geophysical measurements were analyzed to assess liquefaction potential. Within the scope of the study, surface deformation and liquefaction risks were evaluated holistically using geospatial information technologies. As a final product, a multi-risk index was generated for the buildings in the region. This index is highly significant in terms of predicting potential future threats and supporting proactive mitigation measures.