150 research outputs found
Special Issue on “Mapping and Monitoring of Geohazards”
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Assessment of landslide susceptibility in Structurally Complex Formations by integration of different A-DInSAR techniques
Get PDFInstability events are recurring phenomena in Southern Italy due to its geological history and tectonic-geomorphological evolution leading to the occurrence of several formations identified as Structurally Complex Formations (SCFs; Esu, 1977) in a territory mainly composed of densely populated areas also in mountainous and hilly regions. SCFs are clay-dominant terrains that, usually, give origin from very-slow to extremely-slow phenomena (Cruden and Varnes, 1996) with a long evolutionary history made up of multiple reactivations that makes difficult their identification, monitoring and susceptibility evaluation.
The study has been carried out from point-wise (Bisaccia, Costa della Gaveta and Nerano cases) to wide areas (Palermo province case) where crops out SCFs as the Termini sandstones Formation (CARG, 2011), the Varicoloured Clays of Calaggio Formation (Ciaranfi et al., 1973), the Varicoloured Clays Unit (Mattioni et al., 2006) the Sicilide Unit (Vitale and Ciarcia, 2013 and references therein), the Numidian Flysch (Johansson et al., 1998) and the Corleone Calcarenites (Catalano R. et al., 2002).
The aim of this thesis is to produce updated Landslide Inventory Maps and, whenever possible, Landslide Susceptibility Maps following a new approach during the landslide mapping and landslide monitoring stages.
The Landslide Inventory Maps have taken into account the combination of geological, geomorphological, and stereoscopic surveys, as well as engineering geological investigations, namely conventional techniques. In addition innovative Advanced-Differential Interferometry Synthetic Aperture Radar (A-DInSAR) techniques have been used: the Coherent Pixels Technique – CPT (Mora et al., 2003; Blanco et al., 2008), the Intermittent Small BAseline Subset – ISBAS (Sowter et al., 2013) and the Ground-Based Synthetic Aperture Radar.
Finally, the Weight of Evidence method (van Westen, 1993) has been chosen to generate the Landslide Susceptibility Maps only for the point-wise studies.
In the case of Nerano (Province of Naples), the ISBAS analysis on ENVISAT images (for the period 2003-2010) has been carried out and compared with inclinometric and rainfall data. These have revealed several reactivations of a rotational slide + earth flow (Cruden and Varnes, 1996) that involves reworked clay olistostromes and limestone olistoliths inside the Termini sandstones Formation; even in recent years the landslide, despite many engineering works, has given evidence of a continuing activity. The results highlight a very slow movement in the detachment zone (<1 mm/yr), which assumes slightly higher values in the accumulation area (5 mm/yr). The Landslide Susceptibility Map confirms the high levels in the flow track and the accumulation area.
In Bisaccia (Province of Avellino), a conglomeratic slab undergoes a Deep Seated Gravitational Slope Deformation (DSGSD; Pasuto and Soldati, 2013 and references therein) due to the bedrock consolidation, made of the Varicoloured Clays of Calaggio Formation. Here the CPT processing on ENVISAT images (covering the period between 2002 and 2010), displays a vertical displacement for the town center, suffering a progressively increasing velocity from the southern (4.2 mm/yr) to the northern (15.5 mm/yr) portion of the slab that localizes four different sectors. The pattern is confirmed from the building damage map. The landslides susceptibility reaches the highest values in the adjacent valleys and at the edges of each sector.
Multiple datasets have been employed for the Costa della Gaveta case-study (Province of Potenza), these encompass: ENVISAT, TerraSAR-X and COSMO-SkyMed constellations together with Ground Based Synthetic Aperture Radar (GBSAR). The A-DInSAR data have been compared with stereoscopic analysis and the available rainfall and inclinometric data. The analysis allows for the identification of 16 landslides (complexes and earth flows; Cruden and Varnes, 1996) developed in the Varicoloured Clays Unit that show, according to all the existing instruments, velocities between 1.5 and 30 mm/yr. The western side of Costa della Gaveta slope is the portion which suffers the highest landslides susceptibility levels.
In the Province of Palermo (northwestern Sicily) information deriving from A-DInSAR processing, specifically the ISBAS technique, have been focused on three subareas (Piana degli Albanesi, Marineo and Ventimiglia di Sicilia) for a total extension of 182 Km2 where standard A-DInSAR algorithms showed limitations due to the widespread presence of densely vegetated areas. The radar-detected landslides have been validated through field geomorphological mapping and stereoscopic analysis proving to be highly consistent especially with slow phenomena. The outcome has allowed to confirm 152 preexisting landslides, to detect 81 new events and to change 133 previously mapped landslides, modifying their typology, boundary and/or state of activity.
The study demonstrates how a better knowledge of landslide development and their cause-effect mechanisms provided by new Earth Observation techniques is useful for Landslide Inventory and Susceptibility Maps.
The research project has been carried out at the University of Naples "Federico II", including nine months (September 2013 – May 2014) spent in the United Kingdom, at the British Geological Survey under the supervision of Dr. Francesca Cigna and Dr. Jordan Colm and at the University of Nottingham (Department of Civil Engineering), under the supervision of Dr. Andrew Sowter where the ISBAS technique has been recently developed
Environmental baseline monitoring for shale-gas development: insights for monitoring ground motion using InSAR analysis
Get PDFShale gas operations can be contentious, with a degree of uncertainty regarding the effects that they may, or may not, have on the environment. Several countries have moratoria on hydraulic fracturing until its potential effects can be understood better. One area of debate is whether operations could cause ground motion at the surface. This research monitored ground motion prior to operations and compared that baseline to the situation during and after shale gas operations. The test sites are the Vale of Pickering (North Yorkshire) and the Fylde (Lancashire) in the UK. Planning permission was granted in May 2016 to undertake hydraulic fracturing near Kirby Misperton (Vale of Pickering) and in August 2018 at Preston New Road in Lancashire. Hydraulic fracturing has only taken place at Lancashire as it was the only site to also get the hydraulic fracturing plan approved. Complementary Interferometric Synthetic Aperture Radar (InSAR) techniques were used to process archive and current satellite images to detect relative ground motion with millimetric accuracy in rural and semi-urban landcover. The SBAS, ISBAS and RapidSAR processing for the period from 1992 to 2019 (extending 24 years prior to hydraulic fracturing) identified broad regions with little or no surface motion, along with discrete zones of uplift or subsidence. Analysis of the average velocities and time-series data revealed that the motion, where it occurred, related to factors including compressible ground, groundwater abstraction and underground coal mining. This research concluded that the shale gas operations in Lancashire did not alter the baseline ground motion dynamics to date, as detected by InSAR. The successful application of InSAR for detecting and monitoring ground motion at shale gas sites in rural landcover in the UK, where radar coherence has traditionally been a major challenge, serves as a precedent for other regions where baseline monitoring is required
Sovranità e teoria dello Stato in Hobbes e Locke = Sovereignty and State Theory in Hobbes and Locke
Get PDFThis article preliminarily identifies the fundamental characteristics of political power, attributes, and limits of modern State sovereignty. These elements qualify political obligation as a legal relationship aimed at governance and rationalizing collective coexistence. The article then traces the development of the theory of the State by the two main English contractualists of the seventeenth century, Thomas Hobbes and John Locke, and elucidates aspects concerning authority, freedom, rights, and their interrelations as outlined by the systems developed by both philosophers
Sovranità, cittadinanza e diritti umani: il caso colombiano della limpieza social = Sovereignty, Citizenship and Human Rights: The Colombian Case of Limpieza Social
Get PDFDefinite le caratteristiche fondamentali della limpieza social, l’uccisione sistematica in
Colombia di soggetti marginali, lo studio analizza il ruolo svolto dallo Stato nella predisposizione
di condizioni favorevoli allo sviluppo, alla legittimazione e al mantenimento della pratica e le
particolari forme di violenza che in essa si esprimono. L’analisi del fenomeno è poi lo spunto per
una riflessione sul rapporto fra sovranità, pratiche e dispositivi di delimitazione dello spazio
politico, diritti umani e cittadinanza
Filosofia della pena e teoria della società nel pensiero anarchico classico
Get PDFThe article traces the theoretical lines along which anarchist thought has developed concerning the criminal question and punishment. Every libertarian model of social organization faces the challenges of deviance, responding to crime as an offense againstfundamental goods, and conflict. Starting from Stirner, who envisions an informal system of collective defense within the association of the egoists, the author examines arguments at the intersection of criminal philosophy and the theory of the State and society as expressed by Bakunin, Kropotkin, Malatesta,Molinari, Proudhon, Guyau e Godwin
Monitoring land motion due to natural gas extraction: validation of the intermittent SBAS (ISBAS) DInSAR algorithm over gas fields of North Holland, the Netherlands
Get PDFThe differential interferometric synthetic aperture radar (DInSAR) remote sensing technique has proven to be invaluable in the remote monitoring of earth surface movements associated with the extraction and geostorage (subsurface injection) of natural resources (water, oil, gas). However, a significant limitation of this technique is the low density and uneven coverage that may be achieved over vegetated rural environments. The Intermittent Small Baseline Subset (ISBAS) method, an amended version of the established SBAS algorithm, has been designed to improve coverage over rural, vegetated, land cover classes by allowing for the intermittent coherence that is predominant in such areas. In this paper we perform a validation of the ISBAS method over an area of gas production and geostorage in North Holland, the Netherlands. Fortytwo ERS-2 (SAR) C-band images (1995-2000) and 63 ENVISAT (ASAR) C-band images (2003-2010) were processed using the ISBAS technique and the derived measurements enabled the identification of subsidence patterns in rural and urban areas alike. The dominant feature was an area of subsidence to the west of Alkmaar, attributed to natural gas production from the Bergermeer reservoir, where subsidence rates in the region of 3 mm/year were measured. Displacements derived using linear and non-linear surface deformation models were validated with respect to the first order system of levelling benchmarks which form the Amsterdam Ordnance Datum (NAP). It was established that ISBAS products were accurate to within 1.52 mm/year and 1.12 mm/year for the ERS and ENVISAT data sets respectively. Error budgets were comparable to results using persistent scatterers interferometry (PSI) during a validation activity carried out in the European Space Agency Terrafirma project. These results confirm the capability of the ISBAS method to provide a more regular sampling of land motion measurements over gas fields that may be critically used in future to infer the properties of buried, fluid-filled, porous rock
Assessing the feasibility of a National InSAR Ground Deformation Map of Great Britain with Sentinel-1
Get PDFThis work assesses the feasibility of national ground deformation monitoring of Great Britain using synthetic aperture radar (SAR) imagery acquired by Copernicus’ Sentinel-1 constellation and interferometric SAR (InSAR) analyses. As of December 2016, the assessment reveals that, since May 2015, more than 250 interferometric wide (IW) swath products have been acquired on average every month by the constellation at regular revisit cycles for the entirety of Great Britain. A simulation of radar distortions (layover, foreshortening, and shadow) confirms that topographic constraints have a limited effect on SAR visibility of the landmass and, despite the predominance of rural land cover types, there is potential for over 22,000,000 intermittent small baseline subset (ISBAS) monitoring targets for each acquisition geometry (ascending and descending) using a set of IW image frames covering the entire landmass. Finally, InSAR results derived through ISBAS processing of the Doncaster area with an increasing amount of Sentinel-1 IW scenes reveal a consistent decrease of standard deviation of InSAR velocities from 6 mm/year to ≤2 mm/year. Such results can be integrated with geological and geohazard susceptibility data and provide key information to inform the government, other institutions and the public on the stability of the landmas
A methodology to detect and characterize uplift phenomena in urban areas using Sentinel-1 data
Get PDFThis paper presents a methodology to exploit the Persistent Scatterer Interferometry (PSI) time series acquired by Sentinel-1 sensors for the detection and characterization of uplift phenomena in urban areas. The methodology has been applied to the Tower Hamlets Council area of London (United Kingdom) using Sentinel-1 data covering the period 2015–2017. The test area is a representative high-urbanized site affected by geohazards due to natural processes such as compaction of recent deposits, and also anthropogenic causes due to groundwater management and engineering works. The methodology has allowed the detection and characterization of a 5 km2 area recording average uplift rates of 7 mm/year and a maximum rate of 18 mm/year in the period May 2015–March 2017. Furthermore, the analysis of the Sentinel-1 time series highlights that starting from August 2016 uplift rates began to decrease. A comparison between the uplift rates and urban developments as well as geological, geotechnical, and hydrogeological factors suggests that the ground displacements occur in a particular geological context and are mainly attributed to the swelling of clayey soils. The detected uplift could be attributed to a transient effect of the groundwater rebound after completion of dewatering works for the recent underground constructions
Ground motion baseline analysis of the Cheshire UK GeoEnergy Observatory
Get PDFSubsurface geonergy can induce ground motion and seismicity, however a scarcity of observations usually obscures the mechanisms underpinning such behaviour. Here, we analyse Interferometric Synthetic Aperture Radar (InSAR) data from ERS, ENVISAT and Sentinel-1 satellites for the period 1995–2017 and interpret ground deformation in the area of the planned Cheshire UK GeoEnergy Observatory ahead of facility contruction. Ground motion is dominated by the compaction of tidal flat deposits overlying two paleo-valleys, trending NNW–SSE. The western paleo-valley experienced faster subsidence rates in the period 1995–2007, whereas the eastern paleo-valley subsided faster in the period 2016–2017. The research highlights how baseline assessment can help differentiate natural variation from any anthropogenic effects associated with the growth of new subsurface technologies
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