From Regional Deformation to Critical Coastal Infrastructure-Scale Ground Instability Across the Caspian Port Network: Insights from Multi-Temporal Radar Satellite Earth Observation

The Absheron Peninsula contains a dense network of Caspian ports and industrial terminals where vertical land motion (VLM) may affect infrastructure performance. We analyzed fourteen port-associated coastal analysis zones using ascending and descending Sentinel-1 SBAS-InSAR observations from 2017 to 2024. Two-geometry decomposition was used to derive the vertical-deformation component from the complementary ascending and descending viewing geometries. The two-dimensional solution also provides an east–west component, but the present study is specifically focused on vertical land motion; therefore, east–west deformation is not analyzed or presented as a separate result. The two-geometry decomposition does not provide an independently resolved north–south component. VLM was evaluated from peninsula scale to individual port sectors and compared with supplied cumulative GPS vertical-displacement measurements at two stations. Port-mean velocities range from −2.89 to +1.69 mm/year, while localized port measurements reach approximately −23 mm/year and cumulative displacement about −180 mm. These port-scale extremes are distinct from larger isolated regional map values outside the port-associated analysis zones. Strong inter-port and intra-port variability shows that port-wide means can mask localized deformation. The study provides a network-wide radar screening baseline for prioritizing engineering and geodetic follow-up. Because the InSAR solution is relative to automatically selected reference pixels and the ground comparison is limited to supplied cumulative GPS measurements from two stations with incomplete station metadata, the results are interpreted as relative deformation indicators rather than a geocentric structural-safety assessment.