New and existing settlements built on hillslopes weakened by the 2023 Kahramanmaraş earthquake sequence

After major earthquakes, reconstruction and resettlement decisions are often made without fully accounting for cascading hazards, exposing communities to landslide risk. Strong ground shaking can alter hillslope mechanics, yet regional patterns of post-seismic strength change remain poorly constrained. Here we present a physics-based inversion framework that integrates radar satellite deformation measurements with mechanical models based on the Mohr–Coulomb and Hoek–Brown failure criteria to estimate spatial variations in hillslope strength. Applied across 51,287 km2 affected by the 2023 Kahramanmaraş earthquake sequence in Türkiye, the framework quantifies weakening and strengthening of slopes. The resulting strength maps indicate that approximately 1.6 km2 of settlements lie on weakened hillslopes, while about 2.4 km2 of downslope areas may be exposed to slope failure because of their proximity to weakened slopes. New settlements are also being constructed on weakened terrain. These results provide a basis for assessing post-seismic landslide risk and informing safer resettlement. Hillslope strength maps of southern Türkiye produced using a physics-based inversion framework that integrates mechanical models with remote sensing deformation data suggest a total of 4 km2 of settlement area is on, or at risk from, weakened slopes