Soil deformation analysis through fluid-dynamic modelling and DInSAR measurements: a focus on groundwater withdrawal in the Ravenna area (Italy)

This study aims at assessing the deformation processes affecting an area NW of the city of Ravenna (northern Italy), caused by groundwater withdrawal activities. In situ data, geologic and structural maps, piezometric measurements, underground water withdrawal volumes, and satellite C-band SAR data were used to jointly exploit two different techniques: 1) fluid-dynamic and geomechanical modelling (by RSE S.p.A), and 2) Differential Synthetic Aperture Radar Interferometry (DInSAR) analysis (by CNR - IREA). The results of the comparative analysis presented in this work brought new evidence about the contribution of groundwater withdrawal to the total subsidence affecting the area during the 2000-2017 time interval. In particular, they show an increase of the subsidence from year 2000 to 2010 and a decrease from year 2010 to 2017. These results are generally in line with groundwater withdrawal data that report a reduction of the extracted water volumes during the considered temporal interval. Meantime, they show a delay effect in the subsidence process, partially recovered during the 2010-2017 thanks to a stabilisation of the extracted groundwater volumes. The presented results shade new light on the groundwater withdrawal contribution to the subsidence of the analysed zone, although further investigations are foreseen to better clarify the ongoing scenario

Ground deformation and associated hazards in NW peloponnese (Greece)

In the last decades, ground deformations were investigated, analysed and monitored using several methods. As a consequence of a spreading urbanization, several phenomena, e.g. landslide and subsidence, were emphasized or triggered causing not only socio-economic damages, but, in some cases, also casualties. The investigation and mapping of these phenomena are important for both local authorities and civil protection in order to promote a higher conscientious urban planning and to highlight the more hazardous areas. Furthermore, the information are a key point for social development connected to the awareness of the environment and the related risk. The Achaia prefecture, in the north-eastern Peloponnese (Greece), close to the Gulf of Patras, is an area strongly affected by subsidence and landslides. Furthermore, this is an earthquake-prone area, a factor that can trigger some mass movements. For this region, a landslide inventory was realized with the help of the interpretation of Persistent Scatterers data, for the period 1992–2008, and high-resolution optical satellite images, available until 2016, in addition to the investigation of the landslide State of Activity. Moreover, for the coastal area, a section was investigated to evidence subsidence

Integrating seismological data, DInSAR measurements and numerical modelling to analyse seismic events: the Mw 6.5 Norcia earthquake case-study

Questa tesi di dottorato è incentrata sull’analisi dettagliata di sequenze sismiche e sull’applicazione di un approccio multidisciplinare basato sull’integrazione di diverse tecniche geofisiche e geodetiche. Nel contesto di uno studio più generale delle sequenze sismiche, abbiamo concentrato il lavoro sull’analisi ed il confronto di dieci sequenze sismiche (cinque estensionali e cinque compressive), al fine di comprendere le differenze tra questi due ambienti tettonici in termini di durata degli aftershocks. Infatti, il numero di aftershocks decade nel tempo in funzione di vari parametri che risultano essere peculiari di ogni area sismogenetica; tra questi si possono annoverare la magnitudo del mainshock, la reologia crostale e le variazioni dello stress lungo la faglia. Tuttavia, il ruolo esatto svolto da questi parametri nel controllo della durata delle sequenze di aftershocks non è ancora noto. Utilizzando due diverse metodologie, abbiamo evidenziato che l’ambiente tettonico gioca un ruolo primario nell’influenzare la durata degli aftershocks. In media e per una data magnitudo del mainshock, (i) le sequenze di aftershocks sono più lunghe e (ii) il numero di terremoti è maggiore negli ambienti tettonici estensionali rispetto a quelli compressivi. Una possibile spiegazione consiste nel fatto che questa differenza possa essere correlata al diverso tipo di energia dissipata durante i terremoti; in dettaglio, (i) un effetto congiunto di forza gravitazionale e di energia elastica governerebbe i terremoti estensionali, mentre (ii) il rilascio di pura energia elastica controllerebbe i terremoti compressivi. Infatti, le faglie normali operano a favore della gravità, preservando così l'inerzia per un periodo più lungo, e la sismicità dura fino a quando l'equilibrio gravitazionale non viene nuovamente raggiunto dal sistema. Viceversa, i thrusts agiscono contro la gravità, esauriscono la loro inerzia più velocemente e la dissipazione di energia elastica viene controbilanciata dalla forza gravitazionale. Quindi, per sequenze sismiche con magnitudo e parametri reologici paragonabili, gli aftershocks durano più a lungo negli ambienti estensionali poiché la gravità favorisce il collasso dei volumi di hangingwall. Il verificarsi della sequenza sismica del Centro Italia nel 2016 ha fornito un banco di prova per un'analisi dettagliata di un altro terremoto estensionale. Per questo motivo, abbiamo analizzato il terremoto di Norcia (Mw 6.5; Italia Centrale) per aggiungere un’altra sequenza sismica estensionale ai casi di studio precedentemente esaminati. I risultati di questa analisi mostrano che anche la sequenza sismica di Norcia presenta lo stesso comportamento delle altre sequenze estensionali in termini di evoluzione temporale e spaziale degli aftershocks. Inoltre, abbiamo deciso di prendere in considerazione il terremoto di Norcia come caso di studio per l’applicazione di un approccio multidisciplinare, al fine di cercare di comprendere la possibile cinematica e il ruolo della gravità durante i processi di enucleazione degli eventi estensionali. In particolare, abbiamo investigato il terremoto di Norcia, ricorrendo all’utilizzo di dati sismologici, di misure DInSAR e della modellazione numerica. In particolare, abbiamo prima di tutto preso in considerazione gli ipocentri rilocalizzati con 0.1≤Mw≤ 6.5, verificatisi tra il 24 agosto e il 29 novembre 2016 e registrati dalla rete sismometrica INGV; la proiezione su sezioni e la successiva analisi degli ipocentri considerati hanno consentito di comprendere quali strutture geologiche siano state coinvolte durante il processo di enucleazione del terremoto. In seguito, abbiamo analizzato la componente verticale (sollevamento e subsidenza) dei displacements che hanno interessato i blocchi di hangingwall e di footwall della faglia sismogenetica, precedentemente identificata in profondità mediante l’analisi della distribuzione ipocentrale; per fare ciò, abbiamo utilizzato le misure DInSAR ottenute dalla combinazione delle coppie di dati SAR cosismici acquisite dal sensore ALOS-2 lungo orbite ascendenti e discendenti. La mappa di deformazione verticale ottenuta mostra tre aree di deformazione principali: (i) una maggiore subsidenza che raggiunge il valore massimo di circa 98 cm in prossimità delle zone epicentrali vicine alla città di Norcia; (ii) due piccoli lobi di sollevamento che interessano sia il blocco di hangingwall (dove raggiunge valori massimi di circa 14 cm) sia quello di footwall (dove raggiunge valori massimi di circa 10 cm). Partendo da queste evidenze, abbiamo calcolato i volumi di roccia interessati dai fenomeni di sollevamento e subsidenza, evidenziando che quelli coinvolti dal fenomeno di subsidenza sono caratterizzati da valori di deformazione significativamente più alti di quelli affetti da sollevamento (circa 14 volte). Al fine di fornire una possibile interpretazione di questa asimmetria volumetrica, abbiamo esteso l'analisi elaborando un modello numerico 2D basato sul metodo degli elementi finiti, implementandolo in un quadro strutturale-meccanico e sfruttando i dati geologici e sismologici disponibili. I risultati della modellazione sono stati poi confrontati con le misure della deformazione del suolo ottenute dall'analisi DInSAR. Nel corso della realizzazione del modello numerico, abbiamo collaudato gli effetti di geometrie diverse, considerando in particolare due scenari: il primo si basa su una singola faglia immergente a sud-ovest, il secondo su una faglia principale immergente a sud-ovest e una fascia antitetica. In questo contesto, il modello caratterizzato dalla presenza della fascia antitetica fornisce il miglior fit quando confrontato con il pattern cosismico di deformazione superficiale. Questo risultato consente di interpretare i fenomeni di subsidenza e sollevamento causati dal terremoto di Norcia come il risultato di un collasso gravitazionale del blocco di hangigwall lungo la faglia principale e della forza frizionale che agisce in direzione opposta, consistentemente con il meccanismo di doppia coppia lungo il piano di faglia.This Ph.D. thesis is focused on the detailed analysis of seismic sequences and on the application of a multidisciplinary approach based on the integration of several geophysical and geodetic techniques. In the context of a more general study of seismic sequences, we focus this work on the analysis and comparison of five extensional and five compressional seismic sequences to understand the differences between these two tectonic settings in terms of aftershocks duration. In fact, aftershocks number decay through time, depending on several parameters peculiar to each seismogenic regions, including mainshock magnitude, crustal rheology, and stress changes along the fault. However, the exact role of these parameters in controlling the duration of the aftershock sequence is still unknown. Here, by using two methodologies, we show that the tectonic setting primarily controls the duration of aftershocks. On average and for a given mainshock magnitude, (i) aftershock sequences are longer and (ii) the number of earthquakes is greater in extensional than in compressional tectonic settings. We suggest as possible explanation that this difference can be related to the different type of energy dissipated during earthquakes; in detail, (i) a joint effect of gravitational forces and pure elastic stress release governs extensional earthquakes, whereas (ii) pure elastic stress release controls compressional earthquakes. Accordingly, normal faults operate in favour of gravity, preserving inertia for a longer period and seismicity lasts until gravitational equilibrium is reached. Vice versa, thrusts act against gravity, exhaust their inertia faster and the elastic energy dissipation is buffered by the gravitational force. Hence, for seismic sequences of comparable magnitude and rheological parameters, aftershocks last longer in extensional settings because gravity favours the collapse of the hangingwall volumes. The occurrence of the 2016 Central Italy seismic sequence furnishes a test-bed for a detailed analysis of a normal fault earthquake. Therefore, we analyse also the Mw 6.5 Norcia (Central Italy) earthquake to add another extensional seismic sequence to the previously examined case-studies. The results of this analysis show that, with respect to the other considered extensional seismic sequences, also the Mw 6.5 Norcia seismic sequence present the same behaviour about the aftershocks temporal and spatial evolution. Moreover, we decide to take into account the Mw 6.5 Norcia mainshock as case-study for the application of a multidisciplinary approach, in order to understand the kinematics and the role of gravity during nucleation processes of extensional events. In particular, we investigate the Mw 6.5 Norcia earthquake by exploiting seismological data, DInSAR measurements and a numerical modelling approach. In particular, we first take into consideration the relocated hypocentres with 0.1≤Mw≤ 6.5 that occurred between August 24th and November 29th, 2016, recorded by the INGV seismometric network; the projection onto sections and the subsequent analysis of the considered hypocentres allow us to identify the geological structures that were involved during earthquake nucleation process. Then, we retrieve the vertical component (uplift and subsidence) of the displacements affecting the hangingwall and the footwall blocks of the seismogenic faults identified, at depth, through the hypocentres distribution analysis; to do this, we combine the DInSAR measurements obtained from coseismic SAR data pairs collected by the ALOS-2 sensor from ascending and descending orbits. The achieved vertical deformation map displays three main deformation patterns: (i) a major subsidence that reaches the maximum value of about 98 cm near the epicentral zones nearby the town of Norcia; (ii) two smaller uplift lobes that affect both the hangingwall (reaching maximum values of about 14 cm) and the footwall blocks (reaching maximum values of about 10 cm). Also GPS measurements were used to compare the displacements recorded next to the epicentral area. Starting from this evidence, we compute the rock volumes affected by uplift and subsidence phenomena, highlighting that those involved by the retrieved subsidence are characterized by significantly higher deformation values than those affected by uplift (about 14 times). In order to provide a possible interpretation of this volumetric asymmetry, we extend the analysis by running a 2D numerical model based on the finite element method, implemented in a structural-mechanic framework and exploiting the available geological and seismological data. Modelling results are compared with the ground deformation measurements retrieved from the multi-orbit ALOS-2 DInSAR analysis. In the modelling approach, we test the effects of different geometries, by considering two different scenarios: the first is based on including only a single SW-dipping fault, the second includes a main SW-dipping fault and an antithetic zone. In this context, the model characterized by the occurrence of an antithetic zone presents the retrieved best fit coseismic surface deformation pattern. This result allows us to interpret the subsidence and uplift phenomena caused by the Mw 6.5 Norcia earthquake as the result of the gravitational sliding of the hangingwall along the main fault plane and of the frictional force acting in the opposite direction, consistently with the double couple fault plane mechanism

Multi-scale analysis of active landslides using two-pass differential interferometry

Landslides are common features of the landscape of the north-central Apennine mountain range and cause frequent damage to human facilities and infrastructure. Most of these landslides move periodically with moderate velocities and, only after particular rainfall events, some accelerate abruptly. Synthetic aperture radar interferometry (InSAR) provides a particularly convenient method for studying deforming slopes. We use standard two-pass interferometry, taking advantage of the short revisit time of the Sentinel-1 satellites. In this paper we present the results of the InSAR analysis developed on several study areas in central and Northern Italian Apennines. The aims of the work described within the articles contained in this paper, concern: i) the potential of the standard two-pass interferometric technique for the recognition of active landslides; ii) the exploration of the potential related to the displacement time series resulting from a two-pass multiple time-scale InSAR analysis; iii) the evaluation of the possibility of making comparisons with climate forcing for cognitive and risk assessment purposes. Our analysis successfully identified more than 400 InSAR deformation signals (IDS) in the different study areas corresponding to active slope movements. The comparison between IDSs and thematic maps allowed us to identify the main characteristics of the slopes most prone to landslides. The analysis of displacement time series derived from monthly interferometric stacks or single 6-day interferograms allowed the establishment of landslide activity thresholds. This information, combined with the displacement time series, allowed the relationship between ground deformation and climate forcing to be successfully investigated. The InSAR data also gave access to the possibility of validating geographical warning systems and comparing the activity state of landslides with triggering probability thresholds

Monitoring land surface deformation using persistent scatterers interferometric synthetic aperture radar technique

Land subsidence is one of the major hazards occurring globally due to several reasons including natural and human activities. The effect of land subsidence depends on the extent and severity. The consequences of this hazard can be seen in many forms including damaged of infrastructures and loss of human lives. Although land subsidence is a global problem, but it is very common in urban and sub urban areas especially in rapidly developing countries. This problem needs to be monitored effectively. Several techniques such as land surveying, aerial photogrammetry and Global Positioning System (GPS) can be used to monitor or detect the subsidence effectively but these techniques are mostly expensive and time consuming especially for large area. In recent decades, Interferometric Synthetic Aperture Radar (InSAR) technique has been used widely for the monitoring of land subsidence successfully although this technique has several limitations due to temporal decorrelation, atmospheric effects and so on. However, the uncertainties related to InSAR technique have been reduced significantly with the recent Persistent Scatterers Interferometric Synthetic Aperture Radar (PSInSAR) technique which utilized a stack of interferograms generated from several radar images to estimate deformation by finding a bunch of stable points. This study investigates the surface deformation focusing on Kuala Lumpur, a rapidly growing city and Selangor using PSInSAR technique with a set of ALOS PALSAR images from 2007 to 2011. The research methodology consists of several steps of image processing that incudes i) generation of Differential Interferometric Synthetic Aperture Radar (DInSAR), ii) selection of Persistent Scatterers (PS) points, iii) removal of noise, iv) optimization of PS point selection, and v) generation of time series deformation map. However, special consideration was given to optimize the PS selection process using two master images. Results indicate a complete variation of mean line-of-sight (LOS) velocities over the study area. Stable areas (mean LOS=1.1 mm/year) were mostly found in the urban center of Kuala Lumpur, while medium rate of LOS (from 20 mm/year to 30 mm/year) was observed in the south west area in Kuala Langat and Sepang districts. The infrastructures in Kuala Lumpur are mostly stable except in Kuala Lumpur International Airport (KLIA) where a significant subsidence was detected (28.7 mm/year). Meanwhile, other parts of the study area such as Hulu Langat, Petaling Jaya and Klang districts show a very low and non-continuous movement (LOS < 20 mm/year), although comparatively higher subsidence rate (28 mm/year) was detected in the mining area. As conclusion, PSInSAR technique has a potential to monitor subsidence in urban and sub urban areas, but optimization of PS selection processing is necessary in order to reduce the noise and get better estimation accuracy

GROUND DEFORMATION ANALYSIS IN APENNINE AREAS, SEISMICALLY ACTIVE OR ASEISMIC, USING DATA FROM SAR INTERFEROMETRY AND INTEGRATION OF GEOMORPHOLOGICAL AND STRUCTURAL DATA

The core of the study herein has been the analysis of PS-InSAR datasets aimed at providing new constraints to the active tectonics framework, and seismotectonics, of several regions of the Apennines. The analysed Permanent Scatterers datasets result from processing of large amounts of temporally continuous series of radar images acquired with the ERS (1992-2000), ENVISAT (2003-2010) and COSMO SKYMED (2011-2014) satellite missions. Such datasets, which are available in the cartographic website (Geoportale Nazionale) of the Italian Ministry of Environment (MATTM) have been collected through time by the MATTM in the frame of the "Extraordinary Remote Sensing Plan" (Piano Straordinario di Telerilevamento Ambientale, PST-A, law n. 179/2002 - article 27), with the aim of supporting local administrations in the field of environmental policies. The database was realized through three phases: the first one (2008-2009), which involved the interferometric processing of SAR images acquired throughout the country by the ERS1/ERS2 and ENVISAT satellites in both ascending and descending orbits, from 1992 to 2008; the second one (2010-2011) integrated the existing database with the processing of the SAR images acquired by the ENVISAT satellite from 2008 to 2010; the third phase (2013-2015) provided an upgrading and updating of the previously developed database on critical areas, based on StripMap H image acquired with a 16-day recurrence, either in ascending or descending orbit, using the Italian national satellite system, the COSMO SKYMED. With this study, a massive use of Permanent Scatterer datasets is applied for the first time at assessment of ground deformation of large (hundreds of km2 wide) regions of Italy over the last decades, in order to unravelling their current tectonic behaviour. To date in the field of tectonics – in particular, of earthquake geology - the SAR images have been used essentially through the DinSAR technique (comparison between two images, acquired pre- and post-event) in order to constrain the co- and post-seismic deformation (Massonet et al., 1993; Peltzer et al., 1996, 1998; Stramondo et al., 1999; Atzori et al., 2009; Copley and Reynolds, 2014), while the approach that has been used in the case studies that are the object of the research herein is based on analyses of data that (with the exception of the Lunigiana case study) cover an about 20-year long time window. The opportunity of analysing so long, continuous SAR records has allowed detection of both coseismic displacement of moderate earthquakes (i.e., the M 6.3 2009 L’Aquila earthquake, and the M 5 2013 Lunigiana earthquake), and subdued ground displacements - and acceleration – on time scale ranging from yearly to decades. The specific approach used in this study rests on a combination of various techniques of analysis and processing of the PS datasets. In general, as the analyses that have been carried out aimed at identifying motion values with wide areal extent, a statistical filtering has been applied to PSs velocity values in order to discard from the initial, “native”, dataset fast-moving PSs that may be associated with the occurrence of local-scale phenomena (e.g., landslides, sediment compaction, water extraction, etc.). Furthermore, an in depth inspection of time series of PSs from all of the investigated areas has been carried out with the aim of identifying changing (LoS-oriented) motion trends over the analysed time windows. A distinctive feature of this study was the estimation of vertical ground displacements. In fact, while most studies on ground deformation are based on analysis of SAR data recorded along either ascending or descending satellite orbits (thus based on LoS-oriented motions), a specific focus of this study was to obtain - starting from LoS-oriented PS velocity values - displacement values in the vertical plane oriented west-east. In order to evaluate vertical displacements, a geometrical relationship was applied to ascending - descending PSs pairs. As PS from ascending and descending tracks are neither spatially coincident nor synchronous, each image pair was obtained by selecting ascending-descending radar images with a time separation within one month. In the L’Aquila region case study, the combination of data recorded along both the ascending and descending satellite orbits has been crucial to the identification of pre-seismic ground motions, undetected in previous works that – similarly – had addressed assessment of possible pre-seismic satellite-recorded signals. In the various case studies, different kinds of GIS-aided geostatistical analyses were used to extract and synthesise information on ground deformation through the construction of both raster maps of displacement values for the ascending and descending LoS, respectively, and maps of the vertical (z, up - down) component of the “real” displacement vector. In the Campania plain case study, the PS-InSAR data analysis and processing have been integrated by detail scale geomorphological-stratigraphical analysis. Results of analyses of the two independent data sets are consistent, and point to tectonically-controlled ground displacements in a large part of the northern part of the study area (Volturno plain) during the 1992-2010 analysed time span. In particular, the integrated data sets show that the boundaries of the area affected by current subsidence follow fault scarps formed in the 39 ka old Campania Ignimbrite, while the horst blocks of such faults are substantially stable (or slightly uplifting) during the analysed time window. Furthermore, mean rates of current subsidence and long-term (Late Pleistocene to present) mean subsidence rates are comparable, pointing to current vertical displacement assessed through the PS-InSAR data analysis as the expression of the recent tectonics of the analysed sectors of the Campania plain. The Campania plain substantially lacks strong historical seismicity. Such evidence suggests that the detected surface displacements result at least in part from aseismic fault activity. The Monte Marzano case study has allowed assessment of subdued deformation along both the major structures that were activated with the Irpinia 1980 earthquake, i.e. the NE-dipping Monte Marzano fault and the SW-dipping Conza fault, respectively. Ground deformation associated with such structures appears decreasing from the time window covered by the ERS satellites (1992-2000) to that covered by the ENVISAT (2003-2010). These data suggest that post-seismic slip of the M 6.9 has continued until 20 years after the main shock to become very weak in the following ten years. Furthermore, the PS-InSAR data analysis has shown that wide areas located between the Monte Marzano and Conza faults (i.e., in the one that is recognised as the graben structure bounded by those structures) show uplift in the range of 0-2 mm/yr, more evident in the period surveyed by the ERS satellites (1992-2000) and less evident in the 2003-2010 time span (ENVISAT). Such uplift might be related to the occurrence, at depth, of a fluid reservoir that has been independently identified by seismic tomography (Amoroso et al., 2014). In depth analysis of pre-seismic periods have been carried out in three study areas, i.e. those of the 1997 Colfiorito earthquake, of the 2009 L’Aquila earthquake and of the 2013 Lunigiana earthquake. The Colfiorito case study has not provided any significant information on possible pre-seismic ground deformation, most probably due to the PS spatial distribution in that region too much discontinuous to allow identification of both net signals from inspection of the rare and sparse PS time series, and statistically meaningful surface displacement patterns. Both in the L’Aquila and Lunigiana case studies, ground deformation signals in the pre-seismic period have been detected from inspection of PS time series. Pre-seismic ground deformation signals detected in the Lunigiana area (which was affected by a strike-slip faulting earthquake; Eva et al., 2014, Pezzo et al., 2014, Stramondo et al., 2014) are questionable, as they are quite complex and difficult to be interpreted and framed within the local tectonic scenario. Conversely, very clear and net pre-seismic signals have been identified in the region hit by the L’Aquila normal faulting earthquake. There, in the time span predating of some four years the 6th April 2009 main shock, ground deformation with distinct spatial patterns, and orientations, have been detected. In particular, the PS-InSAR analysis has shown that the hanging wall block of the Paganica fault (the surface expression of the structure activated with the main shock; e.g., Galli et al., 2010) has been subject to slow uplift and eastward horizontal motion from 2005 to September/October 2008, and then (October 2008-March 2009) subject to subsidence and westward oriented horizontal motion. Following coseismic collapse, in the early post-seismic period (April-May 2009), subsidence extended eastwards beyond the Paganica fault trace. The region affected by opposite pre-seismic motions covers the area in which the 6th April main shock and most of both foreshocks and aftershocks (Valoroso et al., 2013) were recorded, while the inversion of the pre-seismic displacements is coeval with onset of the foreshocks (October 2008; Di Luccio et al., 2010). In addition, such a region includes both topographic highs and lows. All of such features point to a correlation of the detected motions with the seismic phenomena, and suggest a deep-seated causative mechanism, such as volume changes in response to vertical/lateral fluids migration and fracturing processes at depth, with all phenomena having been documented in connection with the 2009 earthquake in the study region (e.g., Di Luccio et al., 2010; Lucente et al., 2010; Moro et al., 2017). Pre-seismic ground deformation that has been detected in the L’Aquila region could represent a precursor signal of the 2009, M 6.3 earthquake. Such a hypothesis should be tested, in the future, through the continuous monitoring through SAR satellites, but also high-resolution geodetic techniques, of seismically active regions worldwide aimed at detecting the possible occurrence of pre-seismic signals. However, the results of this study point to the long-term (yearly scale) PS-InSAR technique as a tool crucial to the detection of ground deformation in areas struck by recent earthquakes, and to monitoring active – possibly aseismic - structures. Such knowledge may strongly support strategies addressed at territorial planning and mitigation of seismic hazard, and represent an important sustenance for actions ruled by Civil Protection. On the other hand, the results of this study highlight the importance of the existing PS database, and the importance of continuing implementing such an instrument in the future

Applications of Satellite Earth Observations section - NEODAAS: Providing satellite data for efficient research

The NERC Earth Observation Data Acquisition and Analysis Service (NEODAAS) provides a central point of Earth Observation (EO) satellite data access and expertise for UK researchers. The service is tailored to individual users’ requirements to ensure that researchers can focus effort on their science, rather than struggling with correct use of unfamiliar satellite data

Satellite monitoring of harmful algal blooms (HABs) to protect the aquaculture industry

Harmful algal blooms (HABs) can cause sudden and considerable losses to fish farms, for example 500,000 salmon during one bloom in Shetland, and also present a threat to human health. Early warning allows the industry to take protective measures. PML's satellite monitoring of HABs is now funded by the Scottish aquaculture industry. The service involves processing EO ocean colour data from NASA and ESA in near-real time, and applying novel techniques for discriminating certain harmful blooms from harmless algae. Within the AQUA-USERS project we are extending this capability to further HAB species within several European countries