This paper aims to demonstrate that capillary effects and structural collapse can not be ruled out as significant factors in the development of subsidence occurring above gas fields. These phenomena provide sound explanations for continuing surface settlements when reservoir pore pressures stabilize and for additional settlements occurring even after the end of gas production. Conventional subsidence models fail to simulate this settlement behavior. Capillary effects also explain the lower rock compressibilities observed in gas-bearing strata as compared to the values obtained in the laboratory from fully saturated samples. Taking into account these aspects, the observed subsidence above a reservoir in the North Adriatic basin, Italy, is studied in detail.

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This work describes the three-dimensional survey of "Ex Stazione Frigorifera Specializzata": initially used for agricultural storage, during the years it was allocated to different uses until the complete neglect. The historical relevance and the architectural heritage that this building represents has brought the start of a recent renovation project and functional restoration. In this regard it was necessary a global 3-D survey that was based on the application and integration of different geomatic methodologies (mainly terrestrial laser scanner, classical topography, and GNSS). The acquisitions of point clouds was performed using different laser scanners: with time of flight (TOF) and phase shift technologies for the distance measurements. The topographic reference network, needed for scans alignment in the same system, was measured with a total station. For the complete survey of the building, 122 scans were acquired and 346 targets were measured from 79 vertices of the reference network. Moreover, 3 vertices were measured with GNSS methodology in order to georeference the network. For the detail survey of machine room were executed 14 scans with 23 targets. The 3-D global model of the building have less than one centimeter of error in the alignment (for the machine room the error in alignment is not greater than 6 mm) and was used to extract products such as longitudinal and transversal sections, plans, architectural perspectives, virtual scans A complete spatial knowledge of the building is obtained from the processed data, providing basic information for restoration project, structural analysis, industrial and architectural heritage valorization.

Subsidence in a deformation area can be measured in various ways, examples being conventional high-precision leveling, differential InSAR and multi-temporal GPS surveys. Integration of methods can improve results, and is crucial to extract high-precision data. In particular, orthometric and ellipsoid elevations, surveyed at different moments in time, can be compared to yield information on vertical movements when geoid anomalies are known. However, a data checking procedure must be applied if archival orthometric elevations are used, because long-term measurements for many historical benchmarks may have been lost and/or replaced with other points, but at different elevations. This type of checking can be carried out over an area without gravimetric anomalies by modeling geoid undulations and vertical displacements in the time-span used for analysis, excluding points with anomalous values. This procedure was tested and applied in the Po Delta area (northern Italy), historically subject to high subsidence rates: the leveling benchmarks of 1983 were measured with the GPS technique in 2008. After checking of archival data and transformation from ellipsoid to orthometric elevations, comparisons of the same points and interpolations on the study area provided a subsidence map for the 1983-2008 period.

Archival multi-temporal aerial photogrammetry allows to measure displacements of a landslide area when images are co-registered in the same reference system. In this paper we\ud investigated three photogrammetric surveys performed in 1998, 2004 and 2007 in an area of the northern Apennine (Bologna). The study of morphological changes was carried out measuring in stereoscopic vision twelve natural points as roof corner of buildings. Changes were estimated comparing the respective coordinates of the points. Our DEM shows the morphological features and the kinematic of this sliding area with an average grid resolution of 5 m and a maximum elevation error of about 10 cm. Results can improve the geomorphological studies of sliding areas and assist in reducing future hazard

The proposed injection of seawater in a brackish, sandy aquifer\ud lying 600–800 m under the lagoon of Venice to lift Venice itself\ud uniformly up to 30 cm in 10 years raises many problems. We\ud discuss here whether a smooth uplift can be obtained as\ud claimed by the proponents. We first underline the similarities\ud between the Ravenna and Venice case. We then examine the\ud subsidence around Ravenna because of fluid extraction and the\ud measured surface displacements for the period when there is\ud pressure recovery both in the depleted gas reservoir close to\ud Ravenna and in the upper aquifer system. Uniform surface\ud settlements are nowhere observed and strong influence of local\ud heterogeneities cannot be ruled out. The whole picture suggests\ud great caution and the need for much more investigation\ud before undertaking such an injection

Mass movements represent a serious threat to the stability of human structures and infrastructures, and cause loss of lives and severe damages to human properties every year worldwide. Built structures located on potentially unstable slopes are susceptible to deformations due to the displacement of the ground that at worst can lead to total destruction. Synthetic aperture radar (SAR) data acquired by Sentinel-1 satellites and processed by multi-temporal interferometric SAR (MT-InSAR) techniques can measure centimeter to millimeter-level displacement with weekly to monthly updates, characterizing long-term large-scale behavior of the buildings and slopes. However, the spatial resolution and short wavelength weaken the performance of Sentinel-1 in recognizing features (i.e., single buildings) inside image pixels and maintaining the coherence in mountainous vegetated areas. We have proposed and applied a methodology that combines Sentinel-1 interferometry with ground-based geomatics techniques, i.e., global navigation satellite system (GNSS), terrestrial laser scanning (TLS) and terrestrial structure from motion photogrammetry (SfM), for fully assessing building deformations on a slope located in the north-eastern Italian pre-Alps. GNSS allows verifying the ground deformation estimated by MT-InSAR and provides a reference system for the TLS and SfM measurements, while TLS and SfM allow the behavior of buildings located in the investigated slope to be monitored in great detail. The obtained results show that damaged buildings are located in the most unstable sectors of the slope, but there is no direct relationship between the rate of ground deformation of these sectors and the temporal evolution of damages to a single building, indicating that mass movements cause the displacement of blocks of buildings and each of them reacts differently according to its structural properties. This work shows the capability of MT-InSAR, GNSS, TLS and SfM in monitoring both buildings and geological processes that affect their stability, which plays a key role in geohazard analysis and assessment.

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