Post-event Interferometric Synthetic Aperture Radar (InSAR) analysis on a stack of 45 C-band SAR images acquired by the ESA Sentinel-1 satellites from 9 October 2014 to 19 June 2017 allowed the ...identification of a clear precursory deformation signal for the Maoxian landslide (Mao County, Sichuan Province, China). The landslide occurred in the early morning of 24 June 2017 and killed more than 100 people in the village of Xinmo. Sentinel-1 images have been processed through an advanced multi-interferogram analysis capable of maximising the density of measurement points, generating ground deformation maps and displacement time series for an area of 460 km
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straddling the Minjiang River and the Songping Gully. InSAR data clearly show the precursors of the slope failure in the source area of the Maoxian landslide, with a maximum displacement rate detected of 27 mm/year along the line of sight of the satellite. Deformation time series of measurement points identified within the main scarp of the landslide exhibit an acceleration starting from April 2017. A detailed time series analysis leads to the classification of different deformation behaviours. The Fukuzono method for forecasting the time of failure appear to be applicable to the displacement data exhibiting progressive acceleration. Results suggest that satellite radar data, systematically acquired over large areas with short revisiting time, could be used not only as a tool for mapping unstable areas, but also for landslide monitoring, at least for some typologies of sliding phenomena.
Pre- event and event landslide deformations have been detected and measured for the landslide that occurred on 3 December 2013 on the south-western slope of the Montescaglioso village (Basilicata ...Region, southern Italy). In this paper, ground displacements have been mapped through an integrated analysis based on a series of high resolution SAR (Synthetic Aperture Radar) images acquired by the Italian constellation of satellites COSMO-SkyMed. Analysis has been performed by exploiting both phase (through multi-image SAR interferometry) and amplitude information (through speckle tracking techniques) of the satellite images. SAR Interferometry, applied to images taken before the event, revealed a general pre-event movement, in the order of a few mm/yr, in the south-western slope of the Montescaglioso village. Highest pre-event velocities, ranging between 8 and 12 mm/yr, have been recorded in the sector of the slope where the first movement of the landslide took place. Speckle tracking, applied to images acquired before and after the event, allowed the retrieval of the 3D deformation field produced by the landslide. It also showed that ground displacements produced by the landslide have a dominant SSW component, with values exceeding 10 m for large sectors of the landslide area, with local peaks of 20 m in its central and deposit areas. Two minor landslides with a dominant SSE direction, which were detected in the upper parts of the slope, likely also occurred as secondary phenomena as consequence of the SSW movement of the main Montescaglioso landslide.
We present the continuous monitoring of ground deformation at regional scale using ESA (European Space Agency) Sentinel-1constellation of satellites. We discuss this operational monitoring service ...through the case study of the Tuscany Region (Central Italy), selected due to its peculiar geological setting prone to ground instability phenomena. We set up a systematic processing chain of Sentinel-1 acquisitions to create continuously updated ground deformation data to mark the transition from static satellite analysis, based on the analysis of archive images, to dynamic monitoring of ground displacement. Displacement time series, systematically updated with the most recent available Sentinel-1 acquisition, are analysed to identify anomalous points (i.e., points where a change in the dynamic of motion is occurring). The presence of a cluster of persistent anomalies affecting elements at risk determines a significant level of risk, with the necessity of further analysis. Here, we show that the Sentinel-1 constellation can be used for continuous and systematic tracking of ground deformation phenomena at the regional scale. Our results demonstrate how satellite data, acquired with short revisiting times and promptly processed, can contribute to the detection of changes in ground deformation patterns and can act as a key information layer for risk mitigation.
The oldest tide gauge observations date back to the 18th century. Although, globally, they are available in limited number, these centuries-old sea level time series are the only data records ...providing information on the long-period rates of change of the mean ocean surface. Knowledge of the past sea level behavior can contribute key insights to the understanding of climate change impacts. We highlight the greatest importance of monitoring sea-level changes at all spatial scales, from global to local, using terrestrial and space techniques and outline the physical processes, natural and man-induced, responsible for such changes. In general, tide gauge data are made available through different archiving facilities serving both international and national developments. Tide gauges measure local sea-level relative to a benchmark on land, hence, correctly interpreting these observations is challenging since it demands, among other requirements, a proper knowledge of vertical land motions at the stations. In general, it is not easy to find well documented historical data; moreover, benchmarks were not frequently leveled. For more than two decades, space geodetic techniques, such as GNSS (Global Navigation Satellite System) and InSAR (Interferometric Synthetic Aperture Radar), have provided the opportunity to accurately position points in the surroundings of tide gauge sites, potentially giving rise to a large amount of information. However, despite the availability of these techniques, the evolution of the international efforts aiming at realizing consistent observational infrastructures for sea level networks is undergoing only a slow development. In the Mediterranean area, there are a few centennial tide gauge records. Our study focuses on the time series of Alicante, in Spain, Marseille, in France, Genoa, Marina di Ravenna (formerly Porto Corsini), Venice and Trieste, in Italy. After briefly reviewing the gauge types presently in use for sea level measurements, a comprehensive historical description is given for each time series, which may assist understanding an assessment of the problems these stations have experienced over more than one century of operations. Two Italian stations, Marina di Ravenna and Venice, are affected by both natural and anthropogenic subsidence, the latter was particularly intense during a few decades in the 20th century because of ground fluid withdrawal. For these two stations, we have retrieved leveling data of benchmarks close to the tide gauges from the end of the 19th century and, for the last couple of decades, we have evaluated GPS and InSAR heights in close proximity to the stations. The GPS (Global Positioning System) and SAR results were carefully compared. Modeling of the long-period non-linear behavior of subsidence was successfully accomplished by using an ensemble of leveling, GPS and SAR data. After removing the vertical land motions in Venice and Marina di Ravenna, and the inverted barometer effect at all the sites, the linear long period sea-level rates were estimated. The results are in excellent agreement ranging between +1.2 and +1.3mm/year for the overall period from the last decades of the 19th century till 2012. The associated errors, computed by accounting for serial autocorrelation, are of the order of 0.2–0.3mm/year for all stations, except Alicante, for which the error turns out to be 0.5mm/year.
Our estimated rates for the northern Mediterranean, a relatively small regional sea, are slightly lower than the global mean rate, +1.7±0.2mm/year, recently published in the IPCC AR5 (Intergovernmental Panel on Climate Change 5th Assessment Report) (Church et al., 2013), but close enough, if uncertainties are taken into account. It is known that Mediterranean stations had always had lower trends than the global-average ones. Our regional results, however, are in close agreement with the global mean rate, +1.2mm/year, published by Hay et al. (2015) which is currently being discussed by the oceanographic community (see, for example, Hamlington and Thompson, 2015). The six time series were also analyzed by means of the EOF (Empirical Orthogonal Functions) technique over the 1934–2012 common period. As a result, about 50% of the total variance is explained by the first mode, which is characterized by a coherent behavior of the six stations.
This paper illustrates the results of sedimentologic and stratigraphic analyses of the upper Piacenzian–Gelasian fluvial succession exposed in the Neogene–Quaternary Valdelsa Basin (central Italy). ...The succession shows a cyclothemic stacking of gravelly, sandy and muddy lithofacies organized into four monogenic facies associations (A–D). These record depositional environments ranging from braided to low-sinuosity river channels to flood basins. Associations A–D attest to lowstand (A–B), transgressive and high-stand (C–D) depositions in a full cycle of base-level variations. In each association, internal erosional surfaces separate early transgressive association C from the late lowstand association B. The systematic B/C channel scouring is interpreted as the result of a high water/sediment discharge ratio determined by a decrease of coarse-grained sediment supply to the fluvial systems during rise of base level. This erosive surface is conceptually analogous to the ravinement surface sculpted by wave erosion during the transgressive, landward migration of a shoreface. The late transgressive and highstand mud-dominated association D records the flood basin, a depositional environment indicative of a high base level which transformed a former channel belt in a plain dominated by fine-grained sediment settling, bio- and pedoturbation. The studied succession records rhythmic variations of base level and sediment supply to the fluvial systems, in turn regulated by different-rank relative fluctuations of Piacenzian sea level. In this perspective, concepts of sequence stratigraphy and facies analysis are exploited for producing a reliable fluvial sequence stratigraphic model.
•Facies analysis is applied to Piacenzian–Gelasian fluvial deposits.•Monogenic facies associations define specific fluvial depositional environments.•Hybrid facies associations record full cycles of base-level variations.•Hybrid facies associations are discussed in sequence-stratigraphic terms.
This paper introduces InSAR (Interferometric Synthetic Aperture Radar) as an advanced tool for measuring and monitoring surface ground movements over time, with interest in all phases of a tunnel ...project, both in urban and non‐urban areas. Following a preliminary overview of the technology used to compile radar images of the earth's surface, the multi‐image techniques (Persistent Scatterers Interferometry, PSI) and the InSAR algorithm (SqueeSAR) are briefly outlined. Two examples of InSAR data applied to tunnelling projects are presented. In the first case, the integration of InSAR surface measurements into monitoring by conventional methods is discussed as a tool for providing useful information to study the relationship between tunnelling and surface settlements. In the second case, the temporal evolution of ground displacements provided by SqueeSAR is applied in order to understand the link between tunnel excavation and surface movements, along a slope under passed by two large tunnels.
Nelle illustrazioni della Walking city, grandi città-insetto camminano sulla terra, mentre la concretizzazione di quello che sarà il concetto di interconnessione è protagonista del progetto per la ...Plug-in-City: una visione dove le megastrutture popolano il mondo, mentre singole unità abitative, trasfigurate in capsule spaziali, vi si agganciano e sganciano. In queste visioni utopistiche, gli Archigram fondono i codici grafici delle copertine Marvel con lo stile della Pop Art e il linguaggio del fumetto di fantascienza. Il medium grafico, con l’immediatezza del segno e la vivacità dei colori, è lo strumento ideale per restituire un’immagine radicale, capace di far emergere concetti più audaci rispetto a quelli tradizionali. La fusione tra architettura e fumetto diviene così propedeutica alla creazione di una visione futuristica, che fonda le sue radici nell’analisi di una realtà vicina. Anche il mondo del fumetto si occupa per natura del disegno di un’ambiente volto a raffigurare città reali, ideali o veri e propri capricci, dove architetture lontane nel tempo e nello spazio si mescolano, talvolta ad elementi di fantasia o progetti mai realizzati, per formare nuovi immaginari verosimili. Il fumetto, oggi più che mai, non si limita a rispecchiare passivamente la società, ma ne offre una critica aprendo riflessioni anche su questioni architettoniche e urbanistiche. La ricerca propone, con l’analisi dei disegni di alcuni fumetti esemplari, di mettere in luce la creazione di mondi visionari capaci di porre l’accento su specifiche architetture, sulla società e sulla città contemporanea.
Uno dei fondamentali problemi tecnici progettuali riguarda la connessione delle parti componenti gli artefatti. In questo senso l’antica arte della tessitura presenta aspetti interessanti e attuali, ...che si applicano al campo del design e dell’architettura e rimarcano la verità delle affermazioni di Gottfried Semper riguardo la classificazione di materiali e tecniche costruttive. Il connubio tra tecnologia digitale e pattern della tessitura, derivazione dello sviluppo della struttura del nodo/bottone nell’intreccio e poi nel merletto, permette di realizzare strutture tessili applicabili in molteplici settori e dotate di proprietà prestazionali ed estetiche derivate dagli archetipi formali propri della costruzione del tessuto. Fin dall’invenzione nel XVII secolo del telaio Jacquard, l’innovazione tecnologica ha dato notevole impulso al settore tessile. Partendo dalla tradizione cinquecentesca del merletto a fuselli milanese, passando per le interpretazioni novecentesche nell’ambito delle scuole legate al Movimento Moderno e arrivando alle interpretazioni odierne, la ricerca ha l’obiettivo di sperimentare l’applicazione di strutture generate da algoritmi digitali per la produzione dei manufatti e per la valorizzazione di un patrimonio di saperi. Definiti gli elementi di base, i movimenti d’intreccio e il ciclo completo da ripetere nella tradizione del merletto, è possibile ricreare la struttura formale mediante il controllo geometrico dei parametri di forma e movimento.
Ground deformation studies based on Differential GPS (DGPS) measurements and Permanent Scatterers (PS) Interferometric analysis have been conducted in the seismically active area of the Cephallonia ...and Ithaca islands. DGPS measurements for the period 2001 to 2010 revealed horizontal component of deformation generally ranging from 3-8 mm/yr with the largest values at the western and southern parts of the island. Considering the vertical deformation, two periods are distinguished on the basis of DGPS and PS Interferometry: The first one (1992 to 2003) is consistent with anticipated motions associated with the main geological and tectonic features of the island. The second one (2003 to 2010) has been tentatively attributed to dilatancy in which relatively small uplift (2-4 mm/yr) occurred along the southern and southeastern parts of the island, while larger magnitudes (>;4 mm/yr) took place at the western part of Cephallonia. These large magnitudes of uplift over an extended area (>;50 km) are consistent with the hypothesis of dilatancy. On the basis of the analysis of 53 differential ASAR interferograms and the PS product, it has been derived that dilatancy effect should have commenced some time in mid-2005. If this interpretation is correct, it may foreshadow the occurrence of very strong earthquake(s) sometime in the near future.
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