PSI - Issue 84

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

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1. Introduction The long-term stability of transportation networks depends on the geotechnical integrity of the ground on which they are built. Bridges and viaducts are particularly vulnerable to differential ground movement due to their multiple foundation points (Giannico et al. 2022). Land subsidence, defined as the gradual and often uneven downward movement of the Earth's surface, poses a significant risk to infrastructure, especially in alluvial plains and urban areas where human activity accelerates natural compaction (Galloway and Burbey 2011). Subsidence, mainly driven by groundwater over-extraction, subsurface resource exploitation, and urban loading, can cause uneven settlement beneath bridge piers and abutments, leading to excessive stress, misalignment, and bearing failures (Peduto et al. 2017 and Milillo et al. 2018). Consequently, the need for major repairs or emergency closures results in substantial economic and social impacts, underscoring the importance of proactive monitoring and maintenance strategies. Conventional monitoring techniques, such as leveling and Global Positioning System (GPS) measurements, provide high accuracy but are time-consuming, costly, and limited to discrete locations. In contrast, advanced remote sensing techniques, including Persistent Scatterer Interferometric Synthetic Aperture Radar (PS-InSAR), enable continuous, wide-area monitoring under all weather conditions with millimeter-level precision (Crosetto et al. 2016). Satellite InSAR has proven to be a reliable method for surface displacement monitoring, as multi-temporal SAR processing generates accurate displacement maps and time series. Multi-temporal Interferometric Synthetic Aperture Radar (MT-InSAR), and specifically the Persistent Scatterer InSAR (PS-InSAR) technique, has significantly advanced the field by enabling millimeter-scale displacement measurements over large areas with high point density (Ferretti et al. 2001). However, the application of satellite radar interferometry to structural assessment presents both opportunities and limitations, as critically discussed by Talledo et al. (2022). The European Ground Motion Service (EGMS), a component of the Copernicus Land Monitoring Service, addresses these limitations by providing free, standardized, and quality-controlled deformation data across Europe, derived from systematic Sentinel-1 PS-InSAR processing (De Luca et al. 2022). EGMS supplies validated velocity maps and comprehensive displacement time series, establishing itself as a reliable and accessible tool for monitoring geohazards and infrastructure stability. In this study, EGMS data are employed to assess subsidence-related risk for a network of 250 bridges and viaducts in the Caserta territory, in southern Italy. The study area includes the Caserta plain, which is affected by well documented subsidence associated with the compaction of Quaternary alluvial and marine deposits, primarily induced by intensive groundwater extraction (Vilardo et al. 2009 and Pianese et al. 2021). The main objective of this research is to characterize the spatiotemporal patterns of vertical ground motion in the study area between 2018 and 2023 using EGMS data and to correlate these deformation fields with the precise locations of bridge and viaduct foundations to identify assets at-risk. Additionally detailed kinematic analyses of displacement time series are conducted for the most affected bridges, and a replicable EGMS-GIS workflow is proposed for the systematic risk screening of linear transportation infrastructure. 2. Geological settings The geological setting of Caserta, Italy, is defined by extensional tectonics within the peri-Tyrrhenian Campania Plain, which is part of the Southern Apennines mountain belt. The subsurface comprises folded Mesozoic carbonates overlain by Quaternary volcanic and sedimentary deposits, including the Campania Grey Tuff. The region's geology results from the collision between the African and Eurasian plates and persistent volcanic activity. Key geological features include carbonate platforms, thrust and normal faults that form grabens, bauxite deposits produced by weathering, and pyroclastic layers derived from nearby volcanoes such as Campi Flegrei. Subsidence susceptibility is strongly influenced by the regional geological framework (Fig. 1). The Caserta plain is characterized by a thick Pliocene-Quaternary sedimentary succession composed of alternating alluvial sands and gravels, volcaniclastic deposits, and marine-derived silts and clays (Allocca et al. 2007). The map delineates the contrast between the stable, uplifted Miocene carbonate bedrock of the surrounding Apennine margins and the extensive, subsidence-prone Quaternary alluvial and marine deposits filling the plain. These fine grained, highly compressible strata host confined and semi-confined aquifers that have been subjected to prolonged groundwater extraction for agricultural, industrial, and municipal purposes (Pianese et al. 2021). The resulting reduction in pore-water pressure has induced long-term