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Experimentation of new technologies for volcano gravimetry at Mt. Etna
No full textAmong the geophysical techniques used to monitor volcanic unrest, only gravimetry can supply direct information on changes in the distribution of underground mass over time and can thus provide unique insight into processes such as magma accumulation in void space or gas segregation at shallow depths. Despite its great potential, time-variable volcano gravimetry is not widely adopted, mainly due to the high cost of instrumentation and the difficulty in assessing the relatively small volcano-related gravity changes against unfavorable environmental conditions.
Several past studies from Mt. Etna have highlighted the value of gravity observation for improving our understanding of how volcanoes work and characterizing volcanic hazards. In the early stages of application at Mt. Etna, time-lapse and continuous gravity measurements were accomplished using spring gravimeters. Successively, gravimeters based on different technologies have been employed, including superconducting and quantum devices. In most cases, these applications were world firsts at an active volcano.
Here, results from different gravimeter types, that have been used to monitor and study Mt. Etna, are presented. Furthermore, the perspectives opened by emerging technologies are highlighted.PublishedBerlin, GermanyOSV3: Sviluppo di nuovi sistemi osservazionali e di analisi ad alta sensibilit
Sentinel-1 Interferometry and UAV Aerial Survey for Mapping Coseismic Ruptures: Mts. Sibillini vs. Mt. Etna Volcano
No full textThe survey and structural analysis of surface coseismic ruptures are essential tools for
characterizing seismogenic structures. In this work, a procedure to survey coseismic ruptures using
satellite interferometric synthetic aperture radar (InSAR) data, directing the survey using
Unmanned Aerial Vehicles (UAV), is proposed together with a field validation of the results. The
Sentinel-1 A/B Interferometric Wide (IW) Swath TOPSAR mode offers the possibility of acquiring
images with a short revisit time. This huge amount of open data is extremely useful for geohazards
monitoring, such as for earthquakes. Interferograms show the deformation field associated with
earthquakes. Phase discontinuities appearing on wrapped interferograms or loss-of-coherence areas
could represent small ground displacements associated with the fault’s ruptures. Low-altitude flight
platforms such as UAV permit the acquisition of high resolution images and generate 3D spatial
geolocalized clouds of data with centimeter-level accuracy. The generated topography maps and
orthomosaic images are the direct products of this technology, allowing the possibility of analyzing
geological structures from many viewpoints. We present two case studies. The first one is relative
to the 2016 central Italian earthquakes, astride which the InSAR outcomes highlighted quite
accurately the field displacement of extensional faults in the Mt. Vettore–M. Bove area. Here, the
geological effect of the earthquake is represented by more than 35 km of ground ruptures with a
complex pattern composed by subparallel and overlapping synthetic and antithetic fault splays. The
second case is relative to the Mt. Etna earthquake of 26 December 2018, following which several
ground ruptures were detected. The analysis of the unwrapped phase and the application of edge
detector filtering and other discontinuity enhancers allowed the identification of a complex pattern
of ground ruptures. In the Pennisi and Fiandaca areas different generation of ruptures can be
distinguished, while previously unknown ruptures pertaining to the Acireale and Ragalna faults
can be identify and analyzed.Published2514OST5 Verso un nuovo MonitoraggioJCR Journa
Ground motion simulations of historical earthquakes: the case study of the Fabriano (1741, Mw = 6.1) and Camerino (1799, Mw = 6.1) earthquakes in central Italy
No full textThe determination of ground motion is crucial to plan the appropriate emergency activities, especially in areas characterised by an intense seismic history like the Italian peninsula. Ground motion assessment is generally based on the seismological parameters reported in the instrumental and parametric seismic catalogues. Therefore, the computation of shaking scenarios of historical earthquakes is very challenging, due to the poorly constrained variables (i.e., magnitudes, epicentral location, seismogenic sources), derived from the macroseismic intensity. In this study, we propose a novel approach to investigate the location and parametrization of the seismogenic sources of historical earthquakes and derive shaking scenarios. To this aim, the ground motion of two historical events, the Fabriano (1741, Mw = 6.1, Imax IX MCS) and Camerino (1799, Mw = 6.1, Imax IX–X MCS) earthquakes is simulated. In order to include the site response, a Vs,30 map of the Umbria and Marche regions is created from near-surface data. Different causative faults solutions are tested, finally discussing the ideal seismogenic source based on the residual analysis between observed and simulated macroseismic intensities. The resultant shaking scenarios of the two events are obtained by integrating observed intensities and simulations.Published5809–5830OST2 Deformazione e Hazard sismico e da maremotoJCR Journa
Point clouds repeatability and fast scale factor estimates in free SfM surveying: terrestrial application and empirical approach
No full textPrevious experiments highlighted the possible existence of a relation between repeatability of point
clouds obtained from Structure-from-Motion photogrammetry (SfM), represented by the standard
deviation (), and the nominal ground sampling distance (GSD). In particular, the empirical relation
3 ∼ 2.5 GSD was found. For this reason, in-situ tests aimed at studying this relation were carried
out. Data from seven surveys carried out in 2018-2022 time span allowed the comparison between 20
pairs of almost contemporary point clouds, generated by means of relative bundle adjustment (BA)
without ground control points (GCPs) and then relatively scaled and aligned. In this way, the
relation 3 = aGSD was found, where a = 2.5 ± 0.4. This result also suggested the use of the reverse
procedure, where the scale factor (SF) is estimated from the standard deviation of non-metric point
clouds, nmu, by using the relation SFa = aGSD/3nmu. Additional checks proved that SFa differs
from SF by 3%. This error is not acceptable error for length, area or volume measurements, but
the estimated SFa is more than adequate for a fast, rough registration of photogrammetric models
aimed at searching patterns or precursors of incipient phenomena in impervious/inaccessible areas
or in emergency conditions.PublishedRS529OST5 Verso un nuovo MonitoraggioJCR Journa
On the ability of dual-polarimetric SAR measurements to observe lava flows under different volcanic environments
No full textIn this study, we discuss the extra-value of polarimetric information in observing the lava flow. Dualpolarimetric
Synthetic Aperture Radar (SAR) measurements are processed using a polarimetric change detector
that, instead of looking at the variation of the backscatter intensity between a pair of images collected before
and after the event, looks at changes in the polarimetric scattering behavior. We demonstrate that the scattering
changes detected by the proposed polarimetric approach well-correlate with the footprint of the lava flow
provided by external sources. In addition, we also compare the performance of the polarimetric change detector
with conventional single-polarization metrics showing that the former one always outperforms the incoherent
single-polarization measurements. To further demonstrate the robustness of the polarimetric change detectors,
we selected two test cases that refer to vulcanic eruptions calling for completely different environments. The
first one, related to the Etna volcano, calls for a lava flow over a vegetation-free environment; the second one
is related to the Nyiragongo volcano and calls for a lava flow in a vegetated environment. Experimental results
show that the polarimetric change detectors automatically adapt to the changing environment outperforming
the single-polarization detectors.Published103471OSV3: Sviluppo di nuovi sistemi osservazionali e di analisi ad alta sensibilitàJCR Journa
Lettera inedita di Nicola Covelli a Teodoro Monticelli con riferimenti al << Prodromo della mineralogia vesuviana>>
No full textLa missiva di Nicola Covelli a Teodoro Monticelli fa parte del materiale raccolto negli anni del prof. Antonio Parascandola in possesso del nipote Pasquale che gentilmente mi ha omaggiato...Published63-77OS: Terza mission
A Review of Selected Applications of GNSS CORS and Related Experiences at the University of Palermo (Italy)
No full textServices from the Continuously Operating Reference Stations (CORS) of the Global Navigation
Satellite System (GNSS) provide data and insights to a range of research areas such as physical
sciences, engineering, earth and planetary sciences, computer science, and environmental science.
Even though these fields are varied, they are all linked through the GNSS operational application.
GNSS CORS have historically been deployed for three-dimensional positioning but also for the
establishment of local and global reference systems and the measurement of ionospheric and tropospheric
errors. In addition to these studies, CORS is uncovering new, emerging scientific applications.
These include real-time monitoring of land subsidence via network real-time kinematics (NRTK) or
precise point positioning (PPP), structural health monitoring (SHM), earthquake and volcanology
monitoring, GNSS reflectometry (GNSS-R) for mapping soil moisture content, precision farming with
affordable receivers, and zenith total delay to aid hydrology and meteorology. The flexibility of CORS
infrastructure and services has paved the way for new research areas. The aim of this study is to
present a curated selection of scientific papers on prevalent topics such as network monitoring, reference
frames, and structure monitoring (like dams), along with an evaluation of CORS performance.
Concurrently, it reports on the scientific endeavours undertaken by the Geomatics Research Group at
the University of Palermo in the realm of GNSS CORS over the past 15 years.Published5343JCR Journa
Kinetic partitioning of trace cations between zoned clinopyroxene and a variably cooled-decompressed alkali basalt: Thermodynamic considerations on lattice strain and electrostatic energies of substitution
No full textWe present kinetic partitioning data for trace cations measured in zoned clinopyroxene crystals obtained from a variably cooled and decompressed olivine basalt erupted at Mt. Etna volcano in Italy. Supersaturation effects and compositional heterogeneities at the interface melt lead to the development of sector zoning, concentric zoning, and patchy zoning in clinopyroxene crystals. Apparent partition coefficients between compositionally different growth layers and adjacent melts (Di) for isovalent groups of trace elements are tested for internal consistency on the thermodynamic basis of lattice strain (ΔGstrain) and electrostatic (ΔGelec) energies of substitutions. The excess energy of partitioning (ΔGpartitioning) for trace cations in zoned crystals accounts for a kinetic incorporation control leading to large enthalpic effects through distortion of the lattice and changes in the electrostatic forces. ΔGpartitioning depends upon the complementary relationship between ΔGstrain and ΔGelec, which is the most appropriate thermodynamic description for the accommodation of rare earth elements and high field strength elements in the lattice site of zoned crystals. Polyhedral sectors, skeletal forms, and overgrowth zones have Di values settled by the number of charge-balanced and -imbalanced configurations taking place in the lattice site as a function of aluminium in tetrahedral coordination, and crystal structural changes produced by heterovalent cation substitutions. In an energetically unstable macroscopic system ruled by cooling and decompression, thermodynamic requirements for the crystallochemical control of Di encompass the attainment of local equilibrium at the crystal-melt interface via the establishment of small-volume reaction kinetics. The requisite of local interface equilibrium is however susceptible to the anisotropic growth velocity of each specific clinopyroxene surface, thereby giving reason to different energetic properties of the crystallographic site. This axiomatic control requires that transition metal cations partition also in consideration of electronic effects related to the crystal field stabilization energy. The overriding implication is that Di values for trace cations having different size, charge, and electronic configuration serve as sensitive probes of the different crystal growth mechanisms, surface incorporation sites, and arrangements of atoms at the lattice-scale. In this perspective, fractional crystallization modeling of 2011–2013 bulk rock data from lava fountains indicates that the compositional evolution of magmas erupted at Mt. Etna cannot be described by a unique equilibrium value of Di for a given clinopyroxene-melt interface. The leverage of interface kinetics is distinctively dominant along the subvolcanic plumbing system, thereby requiring that values of Di differ for structurally and compositionally distinct zones in clinopyroxene phenocrysts. To successfully interpret the trace element signature of Etnean magmas, the archetypal constancy of partition coefficient at bulk thermodynamic equilibrium must be in some measure reappraised in favor of the establishment of a local interface equilibrium upon highly dynamic crystallization and growth conditions.Published40-66OSV2: Complessità dei processi vulcanici: approcci multidisciplinari e multiparametriciJCR Journa
Operational Earthquake Forecasting in Italy: validation after 10 yr of operativity
No full textThis article has been accepted for publication in Geophysical Journal International ©:The Author(s) 2023. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.Uploaded in accordance with the publisher's self-archiving policy.
All rights reserved.In this paper, we gather and take stock of the results produced by the Operational Earthquake Forecasting (OEF) system in Italy, during its first 10 yr of operativity. The system is run in real-time: every midnight and after each ML 3.5 + event, it produces the weekly forecast of earthquakes expected by an ensemble model in each cell of a spatial grid covering the entire Italian territory. To e v aluate the performance skill of the OEF-Italy forecasts, we consider here standard tests of the Collaboratory for the Study of Earthquake Predictability, which have been opportunely adapted to the case of the overlapped weekly OEF forecasts; then we also adopt new performance measures borrowed from other research fields, like meteorology, specific to validate alarm-based systems by a binary criterion (forecast: yes/no; occurrence: yes/no). Our final aim is to: (i) investigate possible weaknesses and room for improvements in the OEF-Italy stochastic modelling, (ii) provide performance measures that could be helpful for stakeholders who act through a boolean logic (making an action or not) and (iii) highlight possible features in the Italian tectonic seismic activity.Published2502–25196T. Studi di pericolosità sismica e da maremotoJCR Journa
High-resolution spatial analysis of temperature influence on the rainfall regime and extreme precipitation events in north-central Italy
No full textIn the last few years, several works have analyzed rainfall regime changes with the increase of temperature as a result of global warming. These changes, documented mainly in northern Europe, still need to be clarified in the Mediterranean area. Many studies have identified sometimes contradictory trends according to the type of data used, the methodology, and the daily or subdaily types of events. Therefore, an in-depth investigation of the Mediterranean area is required for the definition of more certain future scenarios. In this study, we examined a very large database including >1000 raingauges and thermometers in northern and central Italy to analyze the relationship between temperature and rainfall using the relation Clausius-Clapeyron. Furthermore, we analyzed the relationship between temperature and extreme precipitation events (EPEs, defined as the events higher than the 95th percentile) calculating the temperature anomalies occurred during these events. This large database covers a low rainfall accumulation period (RAP) that allowed us to study the relationship between temperature and rainfall and to distinguish rapid from long events related to rainfall intensity. The results show different relationships between rainfall and temperature in relation to seasons, RAPs, rainfall intensity, and geographical factors. The high spatial density of the database made it possible to identify spatial clusters with homogenous characteristics mainly influenced by geographical factors. With an increase in temperature, the wet season is characterized by a general increase in rainfall with a higher surge for intense and fast events. Instead, the dry season shows a general rainfall decrease for less intense and longer events, but an increase in rapid and more intensive rainfall events. This outcome has further implications involving a future decrease in water availability and an increase of the EPEs, causing an extremization of the climate during the dry season for northern and central Italy.Published163368OSA2: Evoluzione climatica: effetti e loro mitigazioneJCR Journa