PSI - Issue 84

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

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Motion Service (EGMS) has a high density of measurement points, exceeding 500 points per square kilometer in urban areas, thereby ensuring robust statistical representation within each buffer. 3.3. Displacement time-series analysis To move beyond a static, velocity-based assessment and quantify the progressive, cumulative deformation, a detailed kinematic analysis was performed on structures covering the full range of observed deformation severity. Cumulative displacement time series from all EGMS measurement points within a 50-meter buffer around each bridge were extracted, averaged, and detrended to remove long-term linear trends. The 50-meter distance focuses on ground deformation in the vicinity of the bridge foundations, where movements are closely linked to the structure and may induce differential settlement and stress as reported by Milillo et al. (2018). This spatial constraint excludes deformation occurring farther from the structure that is unlikely to influence the foundation behaviour. Moreover, limiting the analysis area reduces the superposition of heterogeneous deformation signals, which is critical for accurately identifying ground motion patterns, particularly near the margins of subsidence bowls. The selected buffer size is also consistent with the spatial representativeness of in situ monitoring instruments, such as tiltmeters and piezometers, thereby facilitating future comparisons between satellite-derived and ground-based observations as shown by Qin and Perissin (2015). The resulting time series were analysed to quantify trend magnitude, identify seasonal components potentially associated with hydrological cycles, and detect signs of non-linear acceleration. EGMS time-series data were segmented into annual intervals from 2019 to 2023. Annual cumulative displacement was computed by differencing the time series at yearly epochs. These annual displacement rasters were subsequently used to map the temporal evolution and possible spatial expansion of subsidence bowls affecting critical infrastructure. 4. Results 4.1. Territorial subsidence patterns The vertical velocity field derived from EGMS data reveals a clear subsidence pattern across the Caserta plain. This deformation is obtained through the decomposition of ascending and descending EGMS line-of-sight (LOS) measurement data and is represented in the map using a color ranging from red (subsidence) to green (stable conditions) The map clearly delineates an extensive subsidence bowl coincident with the alluvial plain, providing the territorial context for infrastructure exposure analysis (Fig. 2).

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Fig. 2. Vertical ground motion velocity, ascending (a) and descending (b) (2018-2023) in the study area