Impact of geohazards on cadastral data: an assessment after the 6 February 2023 Kahramanmaras earthquakes (Türkiye)

Humans set boundaries on land for thousands of years. Cadastre emerged as a system for registering them, whether they are marked on the ground (visible) or unmarked (invisible). Parcel boundary data stored in geospatial databases and supported with registration documents are legally binding in many countries. They are however subject to change physically due to anthropogenic activities and natural processes. Seismic activities inducing surface rupture, lateral spread, landslide, liquefaction, and rockfall are among the main natural causes yielding physical boundary alterations. Spatial pattern and magnitude of alterations depend on the geohazard type and geological characteristics of the area. If a cadastral database is not updated, the physical and registered boundary begins to diverge, leading to uncertainty that needs to be understood by both people and authorities. As a prominent example, the 6 February 2023 Kahramanmaras (Turkiye) earthquakes (Mw7.7 and Mw7.6), which affected a very large region covering approximately 100,000 km2, caused enormous alterations on the physical boundaries of approximately 5 million land parcels. In this study, we analyzed different boundary changes caused by this major event and proposed a conceptual framework based on physical, documentary, and spatial boundary definitions of cadastral parcels with examples from the Kahramanmaras earthquakes. Considering the size of the area and the immense cost of cadastral renovation projects, we analyzed the deformation patterns and possible magnitudes from an interdisciplinary perspective and presented an overview. The study findings provide insights for addressing boundary discrepancies, although additional research is required for comprehensive quantitative assessments across the entire area.