Simone Fiaschi

We live in a constantly changing environment, characterized by climate changes, extreme weather events and the occurrence of more frequent geological hazards that have a strong negative impact on the territory and society, interrupting services, damaging buildings and infrastructure and jeopardizing the life of millions of people worldwide. For this reason, there is the need to build a society resilient to natural-hazards, which can understand how the natural system behaves and responds to natural and human-induced modifications and can adapt to these changes. The monitoring of the territory is necessary to comprehend the triggering factors and the mechanisms of geological hazards and to plan the most suitable actions to prevent and mitigate the risk. The monitoring of geological hazards with conventional ground-based techniques such as Global Positioning System (GPS) and levelling is usually expensive and time consuming, which limits the number of measured points and the overall du...

ABSTRACT Geophysical Research Abstracts Vol. 16, EGU2014-3963, 2014 EGU General Assembly 2014 © Author(s) 2014. CC Attribution 3.0 License. Characterization of seepage surfaces from Space-borne radar interferometry stacking techniques, Southern Dead Sea area, Jordan Giulia Tessari (1), Damien Closson (2), Najib Abou Karaki (3), Simone Atzori (4), Simone Fiaschi (1), Mario Floris (1), Paolo Pasquali (5), and Paolo Riccardi (5) (1) Geosciences Department, University of Padua, Padua, Italy (giulia.tessari@studenti.unipd.it), (2) Department of communication, information, systems and sensors, Royal Military Academy, Brussels, Belgium (damien.closson@yahoo.fr), (3) Environmental & Applied Geology Department, University of Jordan, Amman, Jordan (eqamm@yahoo.com), (4) Istituto Nazionale di Geofisica e Vulcanologia, Centro Nazionale Terremoti, Roma, Italy (simone.atzori@ingv.it), (5) Sarmap S.A., Purasca, Switzerland (ppasquali@sarmap.ch) The Dead Sea is a terminal lake located in a pull-apart basin of the Dead Sea Transform fault zone. It is the lowest emerged place on Earth at about -428 m bsl. Since the 1960s, the over-pumping of its tributaries leads to a decrease in the water level. Eventually, it became more pronounced decades after decades. In 2014, it is more than 1m/year. The overall drop is around 33 m. With salinity ten times greater than the ocean water one, the lake body and its underground lateral extensions act as a high density layer over which the fresh ground waters are in hydrostatic equilibrium. The slope of the interface between saline and fresh waters is ten times shallower than normally expected near the ocean. According to a number of wells along the Jordanian Dead Sea coast, the water table level does not drop at the same speed than the Dead Sea. An increasingly important gradient is constantly being created along the coastal zone. In many places, the fresh ground waters move very rapidly towards the base level to compensate for the imbalance. This statement is supported by a body of observations: a) appearance of vegetation (Tamarisk) in arid areas (precipitation: 50 to 70 mm/year) dominated by salt deposits such as the Lisan peninsula; b) presence of submarine circular collapses visible along the coast. Their diameters decreasing with distance from the shore line; c) appearances of springs and recurring landslides along the coast. With the exception of the submarine features, all these elements are located in the land strip that emerged progressively from the 1960s, 33 m in elevation, ranging from a few decameters up to several kilometers wide. In many places, the surface is characterized by superficial seepages causing subtle to very pronounced subsidence, and sinkholes. In this contribution, we show that advanced differential radar interferometry techniques applied to ERS, ENVISAT and COSMO-SkyMed images stacks are able to underscore the most affected places. The mapping of these areas and their monitoring is essential to set up susceptibility maps in relation with geotechnical issues to existing and future infrastructures such as hotels and dikes.

Is it possible to develop sustainable tourism infrastructures in karst regions where the hydro-geological system is highly perturbed due to the over-exploitation of the water resources? The new resorts area located north-east of the Dead Sea coast in Jordan, is the test-bed used to answer this question. The analysis of Sentinel optical and SAR images, in-situ observations and geological data, has been carried out to produce displacement, vulnerability and thematic maps at cadastral parcel scale. This research demonstrates that without costly remediation work the sustainability is doubtful: the Dead Sea hydro-geological system is more and more unbalanced; an increasing number of hotels and resorts are affected by sinkholes, landslides and subsidence with significant damage to the buildings and the infrastructure. Remote sensing techniques complemented by in-situ and geological data can provide most of the actionable knowledge needed for efficient remediation solutions and for the dev...

In this work, the subsidence in the Ravenna area is estimated by means of the integration between the classical geometric leveling techniques with the more recent SAR (Synthetic Aperture Radar) methodology: Small Baseline Subset (SBAS). This is an interesting area due to the presence of methane reservoirs the exploitation of which has caused in the past an intense subsidence phenomena: at present, the lowering velocities caused by the extraction activity, even if significantly reduced, are still major than the natural ones. The combination of the subsidence and the sea level rise phenomena increases the hydraulic risk of the coastal area. Introduzione Il rilievo della subsidenza nelle aree soggette a deformazione può essere effettuato utilizzando diverse metodologie geomatiche: dalla classica livellazione geometrica al GPS, alla fotogrammetria e all’utilizzo dell’interferometria radar. Le differenti metodologie sono caratterizzate da tempi di esecuzione delle misure, costi, risoluzi...

The Emilia Romagna Region (N-E Italy) and in particular the Adriatic Sea coastline of Ravenna, is affected by a noticeable subsidence that started in the 1950s, when the exploitation of on and off-shore methane reservoirs began, along with the pumping of groundwater for industrial uses. In such area the current subsidence rate, even if lower than in the past, reaches the -2 cm/y. Over the years, local Authorities have monitored this phenomenon with different techniques: spirit levelling, GPS surveys and, more recently, Differential Interferometric Synthetic Aperture Radar (DInSAR) techniques, confirming the critical situation of land subsidence risk. In this work, we present the comparison between the results obtained with DInSAR and GPS techniques applied to the study of the land subsidence in the Ravenna territory. With regard to the DInSAR, the Small Baseline Subset (SBAS) and the Coherent Pixel Technique (CPT) techniques have been used. Different SAR datasets have been exploited...

Landslides threaten more than before the urbanized areas and are a worldwide growing problem for the already affected communities and the local authorities committed to landslide risk management and mitigation. For this reason, it is essential to analyze landslide dynamics and environmental conditioning factors. Various techniques and instruments exist for landslide investigation and monitoring. Out of these, Multi-temporal Synthetic Aperture Radar Interferometry (MT-InSAR) techniques have been widely used in the last decades. Their capabilities are enhanced by the availability of the active Sentinel-1 mission, whose 6-day revisiting time enables near real-time monitoring of landslides. Interferometric results, coupled with ground measurements or other approaches such as numerical modeling, significantly improve the knowledge of the investigated surface processes. In this work, we processed the C-band SAR images of the available European Space Agency (ESA) satellite missions, using ...

<p><span>The morphological variations of unstable areas can be computed using different methodologies that allow performing repeated surveys over time: aerial digital photogrammetry, aerial and terrestrial laser scanning, Synthetic Aperture Radar (SAR) satellites, terrestrial data, and GNSS observations in addition to the classical topographic applications.</span></p><p><span>In this work, the displacements of the Patigno landslide, a deep-seated gravitational slope deformation located in the Northern Apennine (Tuscany, Italy), are evaluated using archival aerial photogrammetry, continuous GNSS observations and multi-temporal SAR satellite data. In particular, the aerial photogrammetric surveys carried out in 1975 (scale 1:13000), 1987 (scale 1:13000), 2004 (scale 1:30000), 2010 (scale 1:10000), and 2013 (scale 1:30000) were analysed. These images have been processed using Socet Set software, in order to estimate the movements of several ground points on the study area. After the extraction of the photogrammetric models, the common reference system was verified by measuring checkpoints in the multi-temporal series located outside the deformation area, choosing well defined artificial points (mainly corners of buildings). Starting from the stereoscopic models, 5 automatic DEMs were extracted with 5 m grid step on the area that included the landslide and its surroundings: from the DEMs it was possible to obtain the corresponding orthophotos; thanks to the good visibility over the whole landslide area in the 1975 model, a DTM was obtained adapting the contour level to the real terrain morphology by means of stereoscopic devices. On the photogrammetric models, the approaches based on the measurements of homologous points in the multi-temporal dataset was adopted: 165 natural points were identified and measured in stereoscopy on each model (mainly corners of buildings); from the comparison of the 3D coordinates, displacement vectors in the four periods 1975-1987, 1987-2004, 2004-2010 and 2010-2013 were obtained. Due to the vegetation cover, the points were measured almost exclusively in the built-up areas of the Patigno, Noce and Val di Termine villages and, to a limited extent, on isolated buildings.</span></p><p><span>The interferometric data acquired by the Sentinel-1A/B satellites from 22-March-2015 to 18-May-2019, and the GNSS data acquired by a continuous station located in the central sector of the landslide (2004/01/01- 2018/12/31) were also analyzed. The GNSS data have been processed with GAMIT/GLOBK and RTKLib software. </span></p><p><span>The results obtained with the three different techniques will be presented along with the estimation of the spatial and temporal evolution of the landslide movement. The area where the continuous GNSS station is located moves with a velocity of about 3 cm/yr, along the direction of maximum slope, in accordance with the displacement rates measured with the photogrammetric and SAR data analysis.</span></p>

<p>Defining land subsidence causes is not an easy task, because ground lowering is a complex phenomenon due to the contribution of different physical processes related to natural contest and to anthropic actions. Indeed, such processes, which are characterized by a specific origin and may act in different spatial and temporal intervals, can overlap giving rise to a single surface land deformation, observable through conventional and innovative monitoring techniques (i.e. high-precision levelling, InSAR and GNSS). Of course, discriminating the individual causes is fundamental for reducing environmental and social harms, especially in deltas and coastal areas, where land sinking, coupled with climatic effects, can induce massive flooding. The present work concerns an application of a multi-component and multi-source approach, recently proposed by some of the authors for studying land subsidence in deltas. Such a methodology is aimed at understanding the processes causing both periodic and permanent components of the vertical land movement and at retrieving more accurate subsidence rates. It consists of three steps, respectively involving: a component recognition phase, based on statistical and spectral analyses of geodetic time series; a source (or physical process) selection phase, based on the comparison with data of different nature; a source validation step, where the selected sources are validated through physically-based models. The proposed procedure has been applied to the permanent component of subsidence in the Po Delta (northern Italy), an area historically affected by land subsidence and influenced by climatic changes, where continuous GNSS data and differential InSAR-derived time series were simultaneously acquired from 2012 to 2017. In particular, the exponential relation found between the mean SAR-derived LOS velocity and the thickness of the Late Holocene prograding deposits, pointed out the key role of the sedimentary compaction process with respect to the spatial distribution of the subsidence rates and confirmed the importance, already highlighted by other authors, of the consolidation of the shallower strata. In order to validate the consolidation process and to quantify also the deeper contributions of tectonics- and isostasy-depending mechanisms, 2D geological models have been constructed along two west-east sections across the central part of the Delta. Finally, the computed subsidence rates have been compared with the geodetic velocities estimated in Taglio di Po and Porto Tolle villages (Rovigo, northern Italy), clarifying the contribution of each geological mechanism to the observed delta subsidence.</p>