Relationship between tremor and volcanic activity during the Southeast Crater eruption on Mount Etna in early 2000

The Southeast Crater of Mount Etna (Italy) was characterized by a violent eruptive activity between 26 January and 24 June 2000. This activity produced 64 lava fountain episodes with repose periods from 3 hours to 10 days. We estimated a volume of about 15–20 106 m3 lava and at least 2–3 106 m3 of tephra. We compared the paroxysmal volcanic activity to its associated seismic signature: The high number of events highlighted a strict correlation between tremor and volcanic activity. Seismic and volcanic characteristics, such as the frequency of occurrence, the duration of lava fountains and the associated tremor energy, suggested the subdivision of the studied period into two stages separated by the 20 February event. Combining volcanic with seismic data, we observed some useful relationships among lava fountain height, sustained column height and Reduced Displacement; in addition, we found that the entire episode was well correlated with the duration of the amplitude increase. Computing the tremor energy linked to each event, the total energy associated with lava fountains episodes results in 76% of the energy released during the whole period. Finally, the different ratios among the overall spectral amplitude of the seismic signals of the stations located at different altitudes suggested to us the elaboration of a simple qualitative model to explain the dynamic behavior of the tremor source during the whole episode

Multispectral pansharpening with radiative transfer-based detail-injection modeling for preserving changes in vegetation cover

Whenever vegetated areas are monitored over time, phenological changes in land cover should be decoupled from changes in acquisition conditions, like atmospheric components, Sun and satellite heights and imaging instrument. This especially holds when the multispectral (MS) bands are sharpened for spatial resolution enhancement by means of a panchromatic (Pan) image of higher resolution, a process referred to as pansharpening. In this paper, we provide evidence that pansharpening of visible/near-infrared (VNIR) bands takes advantage of a correction of the path radiance term introduced by the atmosphere, during the fusion process. This holds whenever the fusion mechanism emulates the radiative transfer model ruling the acquisition of the Earth's surface from space, that is for methods exploiting a multiplicative, or contrast-based, injection model of spatial details extracted from the panchromatic (Pan) image into the interpolated multispectral (MS) bands. The path radiance should be estimated and subtracted from each band before the product by Pan is accomplished. Both empirical and model-based estimation techniques of MS path radiances are compared within the framework of optimized algorithms. Simulations carried out on two GeoEye-1 observations of the same agricultural landscape on different dates highlight that the de-hazing of MS before fusion is beneficial to an accurate detection of seasonal changes in the scene, as measured by the normalized differential vegetation index (NDVI)

Evolution of dwarf galaxies hosting GW150914-like events

Here we present a detailed analysis of the properties and evolution of different dwarf galaxies, candidates to host the coalescence of black hole binary systems generating GW150914-like events. By adopting a novel theoretical framework coupling the binary population synthesis code SEBA with the Galaxy formationmodel GAMESH, we can investigate the detailed evolution of these objects in awell-resolved cosmological volume of 4 cMpc, having aMilkyWay (MW)- like galaxy forming at its centre. We identify three classes of interesting candidate galaxies: MW progenitors, dwarf satellites, and dwarf galaxies evolving in isolation. We find that (i) despite differences in individual histories and specific environments the candidates reduce to only nine representative galaxies; (ii) among them, 3c44 per cent merge into the MW halo progenitors by the redshift of the expected signal, while the remaining dwarfs are found as isolated or as satellites of the MW and their evolution is strongly shaped by both peculiar dynamical history and environmental feedback; (iii) a stringent condition for the environments where GW150914-like binaries can form comes from a combination of the accretion history of their dark matter haloes and the radiative feedback in the high-redshift universe; and (iv) by comparing with the observed catalogues from the DGS and ALLSMOG surveys we find two observed dwarfs respecting the properties predicted by our model. We finally note how the present analysis opens the possibility to build future strategies for host galaxy identification

Guided Deep Decoder: Unsupervised Image Pair Fusion

The fusion of input and guidance images that have a tradeoff in their information (e.g., hyperspectral and RGB image fusion or pansharpening) can be interpreted as one general problem. However, previous studies applied a task-specific handcrafted prior and did not address the problems with a unified approach. To address this limitation, in this study, we propose a guided deep decoder network as a general prior. The proposed network is composed of an encoder-decoder network that exploits multi-scale features of a guidance image and a deep decoder network that generates an output image. The two networks are connected by feature refinement units to embed the multi-scale features of the guidance image into the deep decoder network. The proposed network allows the network parameters to be optimized in an unsupervised way without training data. Our results show that the proposed network can achieve state-of-the-art performance in various image fusion problems.Comment: ECCV 202

Vector casting for noise reduction

We report a new method for the reduction of noise from spectra. This method is based on casting vectors from one data point to the following data points of the noisy spectrum. The noise‐reduced spectrum is computed from the casted vectors within a margin that is identified by an envelope‐finder algorithm. We compared here the presented method with the Savitzky–Golay and the wavelet transform approaches for noise reduction using simulated Raman spectra of various signal‐to‐noise ratios between 1 and 25 dB and experimentally acquired Raman spectra. The method presented here performs well compared with the Savitzky–Golay and the wavelets‐based denoising method, especially at small signal‐to‐noise ratios and furthermore relies on a minimum of human input requirements

Instrumental seismic catalogue of Mt. Etna earthquakes (Sicily, Italy): ten years (2000-2010) of instrumental recordings

Instrumental seismic catalogues are an essential tool for the zonation of the territory and the production of seismic hazard maps. They are also a valuable instrument for detailed seismological studies regarding active volcanoes and, above all, for interpreting the magma dynamics and the evolution of eruptive phenomena. In this paper, we show the first instrumental earthquake catalogue of Mt. Etna, for the period 2000-2010, with the purpose of producing a homogeneous dataset of 10 years of seismological observations. During this period, 16,845 earthquakes have been recorded by the seismic network run by the Istituto Nazionale di Geofisica and Vulcanologia, Osservatorio Etneo, in Catania. A total of 6,330 events, corresponding to approximately 40% of all earthquakes recorded, were located by using a one-dimensional VP velocity model. The magnitude completeness of the catalogue is equal to about 1.5 for the whole period, except for some short periods in 2001 and 2002-2003 and at the end of 2009. The reliability of the data collected is supported by the good values of the main hypocentral parameters through the time. The spatial distribution of seismicity allowed the highlighting of several seismogenetic areas characterized by different seismic rates and focal depths. This seismic catalogue represents a fundamental tool for several research aiming to a better understanding of the behavior of an active volcano such as Mt. Etna

La sequenza sismica nel versante nord-occidentale dell'Etna del 19-27 Dicembre 2009 : evidenze di ricarica magmatica profonda?

E’ stata analizzata la sequenza sismica che ha interessato il versante nord-occidentale dell’Etna nel periodo 19-27 dicembre 2009 (Fig. 1). Essa è stata caratterizzata da oltre 400 scosse di magnitudo compresa tra 1.0 e 4.8, localizzate ad una profondità tra 20 e 30 km, con un rilevante rilascio energetico, come si osserva dalla distribuzione temporale del numero delle scosse e dell’energia ad esse associata nel tempo (Fig. 2). È interessante notare come l’energia rilasciata durante la sequenza risulti essere quasi il triplo dell’energia del periodo sineruttivo 2008, pur essendo pressoché uguale il numero di scosse registrate. In questo settore dell’area etnea, caratterizzato da sismicità profonda, poco frequente e di modesta energia, la modalità di rilascio sismico della sequenza in oggetto costituisce un elemento di novità. Infatti, più del 50% delle scosse si sono verificate nel corso delle prime 24 ore, come tipicamente osservato nel corso di sciami vulcanici sineruttivi. E’ importante evidenziare che nell’area etnea eventi sismici con profondità focali comprese tra i 10 e i 30 km vengono considerati dei veri e propri “markers” di attività vulcanica (e.g. Puglisi et al., 2001), in quanto si verificano abbastanza regolarmente durante i periodi intra-eruttivi e possono essere messi in relazione con i meccanismi di ricarica magmatica (e.g. Bonaccorso, 2001). Essi sono principalmente localizzati nei settori occidentale e meridionale del vulcano lungo strutture orientate NO-SE e NNO-SSE e, occasionalmente, lungo strutture orientate NE-SO (Patanè et al., 2004). Pertanto è ragionevole ipotizzare che il fenomeno oggetto del presente studio possa essere ricondotto ad una fase di ricarica profonda del sistema magmatico etneo

Surface and deep strain at Mt. Etna volcano (Sicily, Italy) during the 2003-2004 inflation phase

We carried out a study of the seismicity and ground deformation occurred on Mount Etna volcano after the end of 2002-2003 eruption and before the onset of 2004-2005 eruption, and recorded by the permanent local seismic network run by Istituto Nazionale di Geofisica e Vulcanologia - Sezione di Catania and by the geodetic surveys carried out in July 2003 and July 2004 on the GPS network. We provided a description of seismicity rate and main seismic swarms which occurred during the investigated period. Mostly of the earthquakes are clustered in two main clusters located on the north-eastern (E-W aligned and above the sea level) and south-eastern (NW-SE aligned and from 3 to 8 Km below the sea level) sectors of the volcano. in order to better understand the kinematic processes of the volcano, the 3D relocation were used to compute fault plane solutions and a selected dataset was inverted to determine stress and strain tensors. The focal solutions on the north-eastern sector show clear left-lateral kinematics along an E-W fault plane, in good agreement with the Pernicana fault kinematics. The focal solutions on the south-eastern sector show a main right-lateral kinematics along a NW-SE fault plane evidencing a roughly E-W oriented compression coupled with a N-S extension. Surface ground deformation affecting Mt Etna and measured by GPS surveys highlights a marked inflation during the same period, mainly visible on the western and upper sectors of the volcano; on the contrary, its eastern side shows an exceptionally strong seawards and downwards motion with displacements ranging from 5 up to 10 cm along the coastline. The 2D geodetic strain tensor distribution was calculated on a 1.5 km spaced grid, in order to detail the strain axes orientation above the entire GPS network. The results of the 2D geodetic strain calculation evidenced the very strong extension (mainly along an- ENE-WSW axis) of the summit area that was already considered as the cause of the 2004-2005 eruption; this main ENE-WSW extension continues throughout the eastern flank, but here coupled with a WNW-ESE contraction, meaning a right-lateral shear along a NW-SE oriented fault plane. The opposite deformation of the eastern sector of the volcano, as measured by seismicity and ground deformation has to be interpreted by considering the different depths of the two signals. Seismic activity along the NW-SE alignment is, in fact, located between 3 and 8 km b.s.l. and it is then affected by the very strong additional EW compression induced by the inflating source located by inverting GPS data just westwards and at the same depth. Ground deformation measured by GPS at the surface, on the contrary, is mainly affected by the shallower dynamics of the eastern flank, fastly moving towards East that produces an opposite (extension) E-W strain. It is also meaningful, confirming the decoupling between the surface and deep strain, that all the seismicity of the south-eastern sector lies beneath the sliding plane already modeled by geodetic data for the same time interval and for the 2004-2006 period and also beneath the deeper one previously modeled during the 1993-1998 period when the eastern flank velocity was much slower

Tornillos at Vulcano: Clues to the dynamics of the hydrothermal system

The number of tornillo events has recently increased at the Vulcano Island, Italy. While only 15 tornillos were recorded during 2004–2006, 584 events occurred in 2007–2008. They were located just below La Fossa Crater at depths ranging between 0.1 and 1 km b.s.l. During two intervals in 2007–2008 increases in the number of tornillos took place at the same time as temperature and geochemical anomalies were observed. The spectral content of the tornillos, generally characterized by one–two dominant spectral peaks near 6 and 10 Hz, varied over time, with changes also noted in the quality factors. The simplest source mechanism proposed for tornillos is the free eigenvibration of a fluid volume within a crack or a conduit. Based on this model, we propose a causal relationship between the temperature and geochemical anomalies and the increases in numbers of tornillos. As the amount of hydrothermal fluids increases during the anomalies, the upward flux of fluids grows. The consequent changes in the pressure, temperature and dynamics of the system of cracks and conduits result in the generation of tornillos. Based on the fluid-filled crack/conduit model, the shallow depths of the sources and the values of the quality factors, the fluid within the resonant crack/conduit was inferred to be an ash–gas or water droplet–gas mixture. Moreover, the observed variations in the wavefield can be caused by small changes in the location of the source, in the source mechanism, or in the medium in between the source and the seismic station. Finally, another peculiar feature of tornillos is the amplitude modulation that can be explained as a result of a beating phenomenon.Published377-3933V. Proprietà chimico-fisiche dei magmi e dei prodotti vulcaniciJCR Journalreserve

Noise estimation in cardiac x-ray imaging: a machine vision approach

YesWe propose a method to automatically parameterize noise in cardiac x-ray image sequences. The aim was to provide context-sensitive imaging information for use in regulating dose control feedback systems that relates to the experience of human observers. The algorithm locates and measures noise contained in areas of approximately equal signal level. A single noise metric is derived from the dominant noise components based on their magnitude and spatial location in relation to clinically relevant structures. The output of the algorithm was compared to noise and clinical acceptability ratings from 28 observers viewing 40 different cardiac x-ray imaging sequences. Results show good agreement and that the algorithm has the potential to augment existing control strategies to deliver x-ray dose to the patient on an individual basis.This work has been performed in the project PANORAMA, funded by grants 335 from Belgium, Italy, France, the Netherlands, United Kingdom, and the ENIAC Joint Undertaking