PSI - Issue 84

Mirza Adeel Zeb et al. / Procedia Structural Integrity 84 (2026) 256–263

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consolidation of clay-rich layers, leading to widespread and progressive land subsidence. This geotechnical context heightens the vulnerability of overlying infrastructure to ground displacement.

Fig. 1. Geological map of the study area.

3. Data and methodology The primary dataset used in this analysis was obtained from the EGMS Basic product (Level 2). For each measurement point, including both Persistent and Distributed Scatterers, the dataset provides geographic coordinates, mean line-of-sight (LOS) velocity calibrated to a stable reference frame, and a complete and cumulative displacement time series. Data from both ascending (Track 6) and descending (Track 95) satellite orbits were incorporated into the area of interest, spanning January 2018 to December 2023. This pre-processed and validated service obviates the need for user-conducted SAR processing, atmospheric correction, or reference point optimization (De Luca et al. 2022). 3.1. Data Preparation and Vertical Decomposition EGMS line-of-sight (LOS) velocity and displacement time-series data were imported into the QGIS environment. Ascending and descending datasets were converted into point feature layers using a common projected coordinate system (ETRS89 / UTM zone 33N). LOS velocities from both acquisition geometries were then combined to derive the vertical displacement component relevant for subsidence analysis. Given that horizontal east-west motion is negligible in this geotechnical setting, vertical velocity (v v ) was est imated using the mean incidence angle (θ) of the Sentinel-1 IW mode Fuhrmann and Garthwaite (2019). 3.2. GIS-based infrastructure exposure analysis To evaluate the potential influence of ground deformation on bridge stability, a buffer zone with a radius of 100 m was defined around each structure. This buffer allows the collection of a sufficient number of Persistent Scatterer (PS) points to compute representative average subsidence rates near each bridge and supports rapid, large-scale screening procedures, as proposed by Peduto et al. (2017). The buffer distance is based on recommendation from geotechnical and foundation engineering practice. For most bridges found on competent soils, the primary zone of stress influence typically extends to approximately 1.5 - 2 times the foundation width in strong soils, but it can be much larger in soft soils like the alluvial clays as reported by Das (2022) that represent the Caserta plain. Given the variability and, in some cases, the lack of detailed information on foundation dimensions, the adoption of a uniform 100 m buffer ensures consistency across all analyzed bridges. This approach facilitates the identification of ground deformation patterns that may induce differential settlements or lateral displacements, as highlighted. Furthermore, the European Ground