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The Effect of Conduit Walls Roughness on Volcanic Jets and Their Seismo‐Acoustic Radiation: An Experimental Investigation
No full textTo explore the effect of conduit roughness on volcanic jet dynamics and on the related
seismo-acoustic radiation we performed a series of shock-tube experiments using pipes with variable inner
surface fractal dimension D. Variable starting pressure produced subsonic to supersonic jets visualized using
high-speed shadowgraph and recorded with an array of accelerometers and microphones. At all starting
pressures, increasing D increases the energy transfer from the gas to the conduit walls, decreasing the jet exit
velocity (Mach number) and, for supersonic cases, the related shock-cell spacing, and increasing the seismic
to acoustic radiation amplitude ratio. The roughness-induced changes in jet velocity and turbulence affect
the dominant sources of the jet noise and modulates the spectral properties of the acoustic signals. From our
study we show that conduit wall roughness is an important and yet largely neglected factor in the dynamics of
explosive volcanic eruptions and their monitored geophysical signals.Publishede2023GL104717OSV2: Complessità dei processi vulcanici: approcci multidisciplinari e multiparametriciJCR Journa
Temporal evolution of the Fogo Volcano magma storage system (Cape Verde Archipelago): a fluid inclusions perspective
No full textThe architecture of the magma storage system underneath Fogo Volcano (Cape Verde Archipelago) is characterised using novel fluid inclusion results from fifteen basanites, spanning the last 120 thousand years of volcanic activity, and encompassing a major flank collapse event at ~73 ka. Fluid inclusions, hosted in olivine and clinopyroxene, are made of pure CO2, and based on their textural characteristics, are distinguished in early (Type I) and late (Type II) stage. Inclusions homogenize to a liquid phase in the 2.8 to 30.8 ◦C temperature range.
Densities values, recalculated assuming an original 10% H2O content at the time of trapping, range from 543 to 952 kg⋅m3, and correspond to entrapment or re-equilibration pressure ranges of 500–595 MPa, 700–740 MPa, and 245–610 MPa respectively for pre-collapse, early post-collapse, and Holocene/historical eruptions. These entrapment pressures are interpreted as reflecting the existence of two main magma accumulation zones at ~25 km and ~ 13–21 km depth, and a zone of fluid inclusion re-equilibration at 9–12 km depth. There is evidence of a complex temporal evolution of the magma system. Historical eruptions, and especially the three most recent ones (occurred in 1951, 1995 and 2014–25), bring fluid inclusion evidence for transient, pre-eruptive shallow (9–17 km depth) magma ponding. Early post-collapse (60 ka) volcanics, in contrast, document fast magma transport from ~25 km, and suggest a reconfiguration of the magma system after the Monte Amarelo collapse event.Published1077302V. Struttura e sistema di alimentazione dei vulcaniJCR Journa
Hydrogeochemistry of trace and rare earth elements in the Caviahue-Copahue Volcanic Complex
No full textThe Caviahue-Copahue Volcanic Complex is one of the most studied active volcanic systems in the South
American Andean range, and yet little research has focused on trace and rare-earth elements of waters, especially
during an eruptive cycle. In this study, we sampled and investigated natural waters from 23 sites (involving the
crater lake, hot springs, streams, rivers, and bubbling pools) in two campaigns in 2017 and 2018, using physi cochemical parameters, major, trace and rare-earth elements concentrations. With this novel dataset, it was
possible to identify, characterize and compare three groups of waters with distinctive hydrofacies. Indeed, the
normalization of water compositions against host rock concentrations showed a particular trace element pattern
for each group of waters. Although the absolute concentrations of the elements in each sampling site changed
from 2017 to 2018, the normalized patterns did not. Boron, As, Cd, Tl, Se, and Te, commonly recognized as
volatile, are the main trace elements that magmatic gases supply to the system headwaters, whereas elements
such as Ca, K, and Ba are affected by precipitation of secondary minerals (gypsum, anhydrite, barite, jarosite, and
alunite). Furthermore, the main river draining the summit volcano shows a steep decrease in As, Cr, and V
concentrations correlated to the precipitation of Fe and Al hydroxysulfates (schwertmannite and basaluminite,
respectively). Moreover, it is the first time that a comparison between the different water groups is made using
the patterns of the rare-earth elements, allowing us to identify and separate depletion patterns due to dilution
processes from those due to precipitation processes.Published121602JCR Journa
Random Forest based estimate to assess the damages of future earthquakes: preliminary results
No full textIn this paper we present a case study where the Random Forest (RF) Classifier, has been used to estimate the damage to buildings caused by a (possible) future earthquake, starting from the data of past earthquakes. This prelaminar work is based on the Shakedado dataset, which contains information on buildings and ground shaking parameters for the six major earthquakes that occurred in Italy between 1981 and 2012. We perform the following two conceptual experiments
E1: Assume that the sequence that hit Emilia has just ended and the data relating to the other major earthquakes happened in the past (L’Aquila, Pollino, and Irpinia) are available, then calculate the level of damage for each building in the Emila dataset.
E2: Assume that the sequence that hit Pollino has just ended and the data relating to the other major earthquakes happened in the past (L’Aquila, Emilia) are available, then calculate the level of damage for each building in the Pollino dataset.
Both training and test datasets contain only masonry buildings located within 10 km of the main shock of each sequence. The results show the RF algorithm’s ability to discriminate between buildings with light/no damage from those with medium/severe damage, with a good accuracy, especially for E1.PublishedOST2 Deformazione e Hazard sismico e da maremotoJCR Journa
Efficient SOM’s Application to Seismic Fumarolic Tremor for the Detection of Anomalous Hydrothermal Activity in Campi Flegrei Volcano (Italy)
No full textIn recent decades, the Campi Flegrei caldera (Italy) showed unrest characterized by in-
creases in seismicity, ground uplift, and hydrothermal activity. Currently, the seismic and hydrother-
mal phenomena are mostly concentrated in the Solfatara–Pisciarelli area, which presents a wide
fumarolic field and mud emissions. The main fumarole in Pisciarelli is associated with a boiling mud
pool. Recently, episodes of a sudden increase in hydrothermal activity and expansion of mud and
gas emissions occurred in this area. During these episodes, which occurred in December 2018 and
September 2020, Short Duration Events (SDEs), related to the intensity of mud pool boiling, were
recorded in the fumarolic seismic tremor. We applied a Self-Organizing Map (SOM) neural network to
recognize the occurrence of SDEs in the fumarolic tremor of Campi Flegrei, which provides important
information on the state of activity of the hydrothermal system and about the possible phreatic
activity. Our method, based on an ad hoc feature extraction procedure, effectively clustered the
seismic signals containing SDEs and separated them from those representing the normal fumarolic
tremor. This result is useful for improving the monitoring of the Solfatara–Pisciarelli hydrothermal
area which is a high-risk zone in Campi Flegrei.Published5505OSV2: Complessità dei processi vulcanici: approcci multidisciplinari e multiparametriciJCR Journa
New Insights Into the Relationship Between Mass Eruption Rate and Volcanic Column Height Based On the IVESPA Data Set
No full textRapid and simple estimation of the mass eruption rate (MER) from column height is essential
for real-time volcanic hazard management and reconstruction of past explosive eruptions. Using 134 eruptive
events from the new Independent Volcanic Eruption Source Parameter Archive (IVESPA, v1.0), we explore
empirical MER-height relationships for four measures of column height: spreading level, sulfur dioxide
height, and top height from direct observations and as reconstructed from deposits. These relationships show
significant differences and highlight limitations of empirical models currently used in operational and research
applications. The roles of atmospheric stratification, wind, and humidity remain challenging to detect across
the wide range of eruptive conditions spanned in IVESPA, ultimately resulting in empirical relationships
outperforming analytical models that account for atmospheric conditions. This finding highlights challenges in
constraining the MER-height relation using heterogeneous observations and empirical models, which reinforces
the need for improved eruption source parameter data sets and physics-based models.Publishede2022GL102633OSV2: Complessità dei processi vulcanici: approcci multidisciplinari e multiparametriciJCR Journa
Reply to the comment by Bolognesi
No full textReply to the comment by Luca BolognesiReply to the comment by Luca BolognesiPublished102754OSA5: Energia e georisorseJCR Journa
A numerical model for gas CO2 migration in a fault zone
No full textUnderstanding whether fractures and faults impact the CO2 migration through the overburden is critical in the
evaluation and monitoring of CO2 geological storage sites. We present a numerical model and workflow to describe the hydraulic behaviour of a fault located in the shallow part of the overburden. This helps to evaluate the sealing potential of the system in case of unwanted CO2 migration toward the surface and to design an efficient monitoring plan. The model configuration is representative of several experiments performed at real sites under quite shallow conditions (50–500 m). The model results, applied to a selected fault outcropping in the Apennines (Italy), show that most of the gas migrates through the high permeable footwall damage zone. A significant amount of gas then dissolves into the water, emphasizing the importance of accurate modelling to assess the hazard of CO2 leakage into near-surface aquifers or to the surface. The occurrence of pressure buildup close to the fault core points out that detailed modelling of the migration conditions is required to predict gas path through a fault zone.Publishedpetgeo2022092OSA5: Energia e georisorseJCR Journa
Diagnostic Process of an Ancient Colonnade Using 3D High-Resolution Models with Non-Invasive Multi Techniques
No full textHere, an avant-garde study of three ancient Doric columns of the precious, ancient Romanesque
church of Saints Lorenzo and Pancrazio in the historical town center of Cagliari (Italy)
is presented based on the integrated application of different non-destructive testing methods. The
limitations of each methodology are overcome by the synergistic application of these methods,
affording an accurate, complete 3D image of the studied elements. Our procedure begins with a
macroscopic in situ analysis to provide a preliminary diagnosis of the conditions of the building
materials. The next step is laboratory tests, in which the porosity and other textural characteristics of
the carbonate building materials are studied by optical and scanning electron microscopy. After this,
a survey with a terrestrial laser scanner and close-range photogrammetry is planned and executed
to produce accurate high-resolution 3D digital models of the entire church and the ancient columns
inside. This was the main objective of this study. The high-resolution 3D models allowed us to
identify architectural complications occurring in historical buildings. The 3D reconstruction with
the above metric techniques was indispensable for planning and carrying out the 3D ultrasonic
tomography, which played an important role in detecting defects, voids, and flaws within the body
of the studied columns by analyzing the propagation of the ultrasonic waves. The high-resolution
3D multiparametric models allowed us to obtain an extremely accurate picture of the conservation
state of the studied columns in order to locate and characterize both shallow and internal defects in
the building materials. This integrated procedure can aid in the control of the spatial and temporal
variations in the materials’ properties and provides information on the process of deterioration in
order to allow adequate restoration solutions to be developed and the structural health of the artefact
to be monitored.Published30985T. Sismologia, geofisica e geologia per l'ingegneria sismicaJCR Journa
Need for harmonized long-term multi-lake monitoring of African Great Lakes
No full textTo ensure the long-term sustainable use of African Great Lakes (AGL), and to better understand the functioning
of these ecosystems, authorities, managers and scientists need regularly collected scientific data
and information of key environmental indicators over multi-years to make informed decisions.
Monitoring is regularly conducted at some sites across AGL; while at others sites, it is rare or conducted
irregularly in response to sporadic funding or short-term projects/studies. Managers and scientists working
on the AGL thus often lack critical long-term data to evaluate and gauge ongoing changes. Hence, we
propose a multi-lake approach to harmonize data collection modalities for better understanding of regional
and global environmental impacts on AGL. Climate variability has had strong impacts on all AGL in the
recent past. Although these lakes have specific characteristics, their limnological cycles show many similarities.
Because different anthropogenic pressures take place at the different AGL, harmonized multilake
monitoring will provide comparable data to address the main drivers of concern (climate versus
regional anthropogenic impact). To realize harmonized long-term multi-lake monitoring, the approach
will need: (1) support of a wide community of researchers and managers; (2) political goodwill towards
a common goal for such monitoring; and (3) sufficient capacity (e.g., institutional, financial, human and
logistic resources) for its implementation. This paper presents an assessment of the state of monitoring
the AGL and possible approaches to realize a long-term, multi-lake harmonized monitoring strategy. Key
parameters are proposed. The support of national and regional authorities is necessary as each AGL
crosses international boundaries.Published101988JCR Journa