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Since the beginning of the 1960s, the urban area of Bologna has experienced land subsidence due to excessive groundwater withdrawals. Ground deformation reached its peak during the 70s of the last century when maximum displacement rates of about 10 cm/year were documented, and significant damage to structures and infrastructures occurred. This process has been intensively monitored over the years, and extensive ground displacement measurements were collected employing increasingly sophisticated techniques, ranging from topographic levelling to GNSS surveys and, since 1992, satellite interferometry. Satellite data, in particular, has given a substantial contribution to the reconstruction of the subsidence process in more recent times, with a progressively higher spatial and temporal resolution towards the newer surveys. The available interferometric data are the results of four consecutive SAR campaigns undertaken by local authorities: 1992 – 2000 (ERS), 2002 – 2006 (ENVISAT), 2006 – 2011 (RADARSAT), 2011 – 2016 (RADARSAT and COSMO-SkyMed), and a fifth survey performed by the UniBo spin-off “Fragile” from the free SENTINEL1 2014 – 2020 data. As long-term data are essential to comprehensively understand the ongoing subsidence process evolution, within this work, a methodology was developed to integrate ground-based and remotely sensed monitoring data collected over the years, and produce continuous cumulative ground displacement time series and maps, depicting the long-term temporal evolution and spatial distribution of the subsidence process, respectively. The results obtained through the adopted processing chain highlight that the long-term ground displacement field well agrees with the 3D geological model of the area and that the cumulative subsidence and displacement rates temporal evolution nicely matches the pluriannual trend of the piezometric and groundwater pumping time series.

Since the beginning of the 1960s, the urban area of Bologna has experienced land subsidence due to excessive groundwater withdrawals. Sinking reached its peak in the 70s of the last century when the subsidence rate attained the maximum value of about 10 cm/year, and significant damages to structures and infrastructures occurred. This process has been intensively monitored over the years, and extensive ground displacement data were collected employing various increasingly sophisticated techniques, ranging from topographic levelling to GNSS surveys and, since 1992, to satellite interferometry. Satellite data, in particular, allowed an accurate reconstruction of the land subsidence process. The available interferometric data are the results of three different SAR campaigns undertaken by local authorities in which the PSInSAR technique was adopted: 1992 – 2000 (ERS), 2002 – 2006 (ENVISAT) and 2006 – 2011 (RADARSAT). Within this work, a new InSAR survey from the free SENTINEL1 2014 – 2020 ascending and descending orbits data was undertaken by the UniBo spin-off “Fragile”. The software GMTSAR was used to process each interferogram and then a Small Baseline (SBAS) approach was followed to resolve the ground displacements over time. Great attention was paid to the choice of reference pixels on the existing buildings and structures, in order to maximise their density in the study area, and to the definition of the considered time span ranging from 6 to 365 days, allowing to analyse both quicker and slower ground movements. Compared to previous surveys, the displacement map obtained by Sentinel has a much higher spatial and temporal resolution, thus leading to a detailed interpretation of the ongoing subsidence. Results show that the displacement field well agrees with the 3D geological model of the area and that the temporal evolution of the subsidence rate nicely matches the piezometric level and groundwater pumping temporal series.

Despite the growing employment of Remote Sensing (RS) techniques in paleoenvironmental studies, the stratigraphic interpretation of RS-derived paleodrainage traces is still an open issue, as their relation to subsurface is largely unexplored. Here we applied a multi-data analysis approach, including publicly available optical images from different satellites (Landsat, ASTER, Sentinel, Hyperion), LiDAR-derived Digital Terrain Model (DTM), soil reflectance spectra and facies core data, which succeeded in revealing a paleodrainage system buried beneath a 200-sq km wide wetland (the Mezzano Lowland-ML) of the Po coastal plain (northern Adriatic Sea, Italy). Data integration in a GIS environment allowed the 3D mapping of numerous and temporally persistent meandering traces. From distal to proximal locations, the RS-derived traces show a hierarchical organization, in terms of sinuosity and width, and form a dense and dendritic pattern typical of a tidally-influenced system. Surface and subsurface cross-investigation of two meandering traces through soil reflectance spectra and core stratigraphy reveal that these landforms represent the surface expression of buried channels that eroded the underlying lagoonal succession, with lateral transition to intertidal deposits. LiDAR-detected micro-morphologies related to paleomeanders evolution strongly influenced the spatial distribution of mid-late Holocene peat-bearing lithofacies (i.e., salt marsh and swamp), and hence soil moisture distribution, inducing the sharp radiance contrasts (traces) detected by satellite sensors on the surface. On-trace areas invariably lack peat deposits and record the top of 3–4 m-thick channel-fill sands, some 2–4 m below the ground level. In contrast, out-of-trace areas are characterized by organic-rich soils that cap a 2.5–3.5 m-thick succession of intertidal-supratidal peat deposits, accumulated in depressed areas lateral to the channel-levee complex. We conclude that in the early stage of Po Delta construction, between ca. 6000–2500 cal yr BP, two distinct tidal-influenced drainage networks fed the Mezzano Lowland lagoon under a predominantly autogenic control. These findings indicate the suitability of a low-cost RS-stratigraphic approach to improve the reconstruction of past paleogeographic scenarios buried beneath deltaic lowlands, shedding new light on the evolution trends of coastal landforms, environments and sedimentary patterns under highstand conditions.

This paper investigates the role played by geomorphological and tectonic processes affecting a portion of an active mountain belt in causing the occurrence of different types of landslides developed in flysch bedrock. The adopted multidisciplinary approach (geomorphology, geology and geophysics) allowed to recognize in a portion of the Northern Apennines of Italy different types of landslides that developed in response to slope dynamics, in turn dependent on broader regional-scale tectonic processes. Sedimentary bed attitude, local tectonic discontinuities and lithology only partially influenced the type of landslides, which have been deeply affected by the activity of regional-scale antiform that controlled the hillslope geomorphic evolution in different ways. The growth of this structure and the tilting of its forelimb produced gently dipping slopes that approached the threshold angle that can cause the occurrence of (mainly) translational rockslides. Conversely, high-angle normal faulting parallel to the antiform axis (related to a later stage of activity of the antiform itself) strongly controlled the stream network evolution and caused the watercourses to deeply incise portions of their valleys. This incision produced younger steep valley slopes and caused the development of complex landslides (roto-translational slides-earth/debris flow). The results of the integrated study presented in this paper allowed to distinguish two main types of landslides whose development reflects the events that led to the geomorphological and geological evolution of the area. In this perspective, within the study area, landslides can be regarded and used as indicators of broader-scale recent tectonic processes.

International audience; Based on the review of the available stratigraphic, tectonic, morphological, geodetic, and seismological data, along with new structural observations, we present a reappraisal of the potential seismogenic faults and fault systems in the inner northwest Apennines, Italy, which was the site, one century ago, of the devastating Mw ~6.5, 1920 Fivizzano earthquake. Our updated fault catalog provides the fault locations, as well as the description of their architecture, large-scale segmentation, cumulative displacements, evidence for recent to present activity, and long-term slip rates. Our work documents that a dense network of active faults, and thus potential earthquake fault sources, exists in the region. We discuss the seismogenic potential of these faults, and propose a general tectonic scenario that might account for their development.