Dynamics of Vulcano Island investigated by long-term (40 years) geophysical data

Vulcano island is a composite volcanic edifice located in the south-central sector of the Aeolian Archipelago (Tyrrhenian Sea, Italy) and it is an important tourist destination. Historic activity has been characterized by frequent transitions from phereatomagmatic to minor magmatic activity. The last eruption in 1888-90 was characterized by energetic explosive pulses and defines the “vulcanian” type of activity. Since then, volcanic activity has taken the form of fumarolic emanations of variable intensity and temperature, mainly concentrated at “La Fossa” crater, with maximum temperatures ranging between 200° and 300° C; temperature increases and changes in the gas chemistry, were often observed. The most recent episode began in the 80’s when fumarole temperature progressively increased to 690°C in May 1993. Vulcano is active and this favoured monitoring and research studies, in particular focussed on the most recent structures. In the frame of DPC-INGV “V3” project, we investigate the Vulcano dynamics through ca. 40 years of ground deformation and seismicity data collected by the discrete and continuous INGV monitoring networks. We considered levelling, GPS, EDM, seismic and tilt data. EDM and levelling measurements began in the middle 1970s and since the late 1990s the EDM benchmarks have been measurered using GPS. We observed three scales of ground deformation: the first one seems to be linked to the regional tectonics, with a general transpressive kinematics; the second one affects the northern half of the island and could be related to the caldera dynamics; the third one affects only the cone of La Fossa. Regional tectonic stress seems to play an important role in the transition of the volcanic system from a phase of stability to a phase of unrest, inducing the heating and the expansion of shallow hydrothermal fluids. Ground deformation at Vulcano may be linked to the geothermal system rather than magmatic sources

Heat flux-based strategies for the thermal monitoring of sub-fumarolic areas: Examples from Vulcano and La Soufrière de Guadeloupe

Although it is relatively easy to set-up, the monitoring of soil temperature in sub-fumarolic areas is quite rarely used to monitor the evolution of hydrothermal systems. Indeed, measurements are highly sensitive to environmental conditions, in particular daily and seasonal variations of atmospheric temperatures and rainfalls, which can be only partially filtered by the established statistical analysis. In this paper, we develop two innovative processingmethods, both based on the computation of the heat flux in the soil. The upward heat flux method (UHF), designed for dry environments, consists in computing both the conductive and convective components of the heat flux between two thermocouples placed vertically. In the cases of wet environments, the excess of total heat method (ETH) allows the integration of rain gauges data in order to correct the heat balance fromthe superficial cooling effect of the precipitations. The performances of both processing techniques are faced to established methods (temperature gradient and coefficient of determination) on soil temperature time series from two test volcanoes. At La Fossa di Vulcano (Italy), the UHF method undoubtedly detects three thermal crises between 2009 and 2012, enabling to quantify not only the intensity but also the precise timing of the heat flux increase with respect to corresponding geochemical and seismic crises. At La Soufrière de Guadeloupe (French Lesser Antilles), despite large rainfalls dramatically influencing the thermal behavior of the soil, a constant geothermal heat flux is retrieved by the ETH method, confirming the absence of fumarolic crisis during the observation period (February–August 2010). Being quantitative, robust, and usable in almost any context of sub-fumarolic zones, our two heat flux-based methods increase the potential of soil temperature for the monitoring, but also the general interpretation of fumarolic crises together with geochemical and seismological observations. A spreadsheet allowing direct computation of UHF and ETH is provided as supplemental material.Published122-1342V. Struttura e sistema di alimentazione dei vulcaniJCR Journa

Genesis and mechanisms controlling tornillo seismo-volcanic events in volcanic areas

Volcanic activity is often preceded or accompanied by different types of seismo-volcanic signals. Among these signals, the so-called tornillo (Spanish for "screw") events are considered to belong to a unique class of volcano-seismicity characterised by a long-duration coda, amplitude modulation and high-quality factor. These data constitute important evidence for the gas fraction inside magmatic fluids. However, the mechanism behind this unique signal remains not fully understood. Here we report new laboratory evidence showing that two different processes have either scale-invariant or scale-dependent effects in generating tornillo-like events. These processes are respectively the gas pressure gradient, which triggers the event and regulates the slow decaying coda, and the fluid resonance into small scale structures which, in turn, control the frequency content of the signal. Considering that the gas pressure gradient is proportional to the fluid flow, these new findings, as applied to volcanoes, provide new information to better quantify both gas rate and volume, and the dimension of the resonator.Publishedid 73385V. Processi eruttivi e post-eruttiviJCR Journa

A Hidden Eruption: The 21 May 2023 Paroxysm of the Etna Volcano (Italy)

On 21 May 2023, a hidden eruption occurred at the Southeast Crater (SEC) of Etna (Italy); indeed, bad weather prevented its direct and remote observation. Tephra fell toward the southwest, and two lava flows propagated along the SEC’s southern and eastern flanks. The monitoring system of the Istituto Nazionale di Geofisica e Vulcanologia testified to its occurrence. We analyzed the seismic and infrasound signals to constrain the temporal evolution of the fountain, which lasted about 5 h. We finally reached Etna’s summit two weeks later and found an unexpected pyroclastic density current (PDC) deposit covering the southern lava flow at its middle portion. We performed unoccupied aerial system and field surveys to reconstruct in 3D the SEC, lava flows, and PDC deposits and to collect some samples. The data allowed for detailed mapping, quantification, and characterization of the products. The resulting lava flows and PDC deposit volumes were (1.54 ± 0.47) × 106 m3 and (1.30 ± 0.26) × 105 m3, respectively. We also analyzed ground-radar and satellite data to evaluate that the plume height ranges between 10 and 15 km. This work is a comprehensive analysis of the fieldwork, UAS, volcanic tremor, infrasound, radar, and satellite data. Our results increase awareness of the volcanic activity and potential dangers for visitors to Etna’s summit area

Geophysical monitoring of Stromboli volcano: insight into recent volcanic activity

Stromboli is an open conduit strato-volcano of the Aeolian archipelago (Italy), characterized by typical Strom-bolian explosive activity, lasting for several centuries, and by the emission of huge amounts of gas. The normalactivity of Stromboli is characterized by some hundreds of moderate explosions per day. Major explosions, whichlaunch scoria up to hundreds of meters from the craters, lava flows and paroxysmal explosions, which producelarge ballistic blocks, sometimes take place. During the effusive eruption in 2002 - 2003, which caused a tsunamiwith waves of about 10 meters high along the coasts of the Island, the monitoring system was enhanced. In 2006INGV has added two Sacks-Evertson borehole volumetric dilatometers to the surveillance system, in order to mon-itor changes in the local strain field by measuring areal strain. Today we have a large amount of geophysical dataand observations that allow us to better understand how this volcano works. After a period of low explosive activitystarted in mid-2014, Stromboli has shown a more intense explosive activity in the last few months. During the re-cent phase of increased activity, the geophysical monitoring system detected four major explosions occurred on 26July, 23 October, 1 November and 1 December 2017, respectively. The current phase of reawakening of Strombolivolcano has led the Italian civil protection authorities to decree the "attention" alert level (yellow) on the Island.PublishedVienna, Austria1IT. Reti di monitoraggio e sorveglianz

Characterization of an Active Fault through a Multiparametric Investigation: The Trecastagni Fault and Its Relationship with the Dynamics of Mt. Etna Volcano (Sicily, Italy)

The Trecastagni Fault (TF) is an important tectonic structure in the middle-lower southern flank of Mt. Etna volcano. It is characterised by evident morphological slopes with normal dip-slip ruptures that directly affect roads and buildings. The TF plays a key role in the complex framework of the volcano dynamics since it represents part of the southern boundary of the unstable sector. Seismic surveys have been performed on three different areas of the fault to gain insights into the seismic stratigraphic structure of the subsoil. We considered the seismic activity of a sector of the territory affecting the surface evidence of the Trecastagni Fault in the period between 1980 and 2021 in order to highlight the main seismic release and define the space–time distribution of seismicity. Most of the seismicity is located in the north-western portion, while the central and southern sectors are characterised by low seismic activity. The strongest earthquakes occur mainly within the first 5 km of depth in the form of swarms and/or isolated shocks. Ground deformation techniques (levelling, In-SAR and two continuous extensometers) evidence a continuous aseismic slip of the TF that is interrupted by short accelerations accompanied by shallow seismicity. The Trecastagni Fault dynamics are strictly linked to magma pressurisation and intrusive episodes of Mt. Etna that induce additional stress and promote its slip along the fault plane. Multidisciplinary data analysed in this work, evidenced the dual behaviour of the fault, from aseismic creep to stick-slip, and the relation with magmatic activity, also suggesting the time delay in the response of the fault after the intense stress induced by dyke intrusion

Electronic properties of neuroleptics: ionization energies of benzodiazepines

International audienceVertical ionization energies (VIEs) of medazepam, nordazepam and their molecular subunits have been calculated using the electron propagator method in the P3/CEP-31G* approximation. Vertical electron affinities (VEAs) have been obtained with a ∆SCF procedure at the DFT-B3LYP/6-31+G* level of theory. Excellent correlations have been achieved between IE and IE, allowing reliable assignment of the ionization processes. Our proposed assignment differs in many instances from that previously reported in the literature. The electronic structure of the frontier Dyson orbitals shows that the IE and EA values of the benzodiazepines can be modulated by substitution at the benzene rings. Hardness values, evaluated as (IE − EA)/2, follow the trend of the experimental singlet transition energies. Medazepam is a less hard (i.e., less stable) compound than nordazepam

Buried active faults in the Zafferana Etnea territory (south-eastern flank of Mt. Etna): geometry and kinematics by earthquake relocation and focal mechanisms

We relocated seismicity that occurred from 2000 to 2005 inside a sector of Mt. Etna, comprising the town of Zafferana Etnea, using the double-difference technique. This approach revealed some spatial clusters of events at depths of 3.0 km to 5.5 km b.s.l., which suggested NE-SW-oriented and NNW-SSE-oriented active structures located west and north-west with respect to Zafferana Etnea. We also calculated 64 fault plane solutions, and azimuth and dip distributions of maximum compression P axes. The data include eight events with magnitudes between 3.1 and 3.7 that caused damage to Zafferana Etnea. This approach has allowed the definition of the geometry of structures that show no surface evidence, but are potentially hazardous for this territory. These faults might be linked to the regional tectonics, although they were activated by stress changes related to a general pressurizing of the Mt. Etna magma system between 2000 and 2005

Seismic data of Mt. Etna: the contribution of in situ data to MED-SUV Project

In the context of main objectives of the MED-SUV Project’s “Work Package 3”, one goal of the sub-task 3.2.4 is to provide already available in situ seismic data concerning Mt. Etna volcano. In particular, this sub-task envisages sharing data detected during the period 2005-2011. Three kinds of seismic data have been selected for sharing with MED-SUV users: i) raw continuous signals from broadband digital stations; ii) an earthquake catalogue, concerning local shocks hypocentres calculated by expert personnel at Osservatorio Etneo (INGV-OE) by means of off-line analysis of digital seismograms; iii) the RMS amplitude value of the continuous seismic signal. Regarding the first data type, starting from the original SUDS format seismic records (each 1-min long), stored as compressed files in the INGV-OE repository, we produced files, each 1-h long, in standard SAC format. Several working phases were performed to achieve the objective: copying data from the original repository to a temporary storage, decompressing data files, extracting the records of selected seismic stations, converting data from SUDS to SAC format, and finally moving the obtained SAC files in the MED-SUV repository. Overall, about 3.5E6 SUDS files were processed, obtaining about 2E6 SAC files, that overall amount to about 2.6 TB. If needed, raw continuous signals for sharing can also be provided in standard miniSEED format. The earthquake catalogue reports parametric information (e.g. latitude, longitude, depth, magnitude) on the hypocentres of ca. 800 earthquakes. This catalogue refers to shocks with magnitude greater than or equal to 2.0 and error threshold not greater than particular values (e.g. horizontal and vertical hypocentral errors less than or equal to 2.0 km, RMS travel-time residual less than or equal to 0.35s, etc.). These data are provided in ASCII format. Finally, RMS amplitude values of the continuous seismic signal have been calculated by an automatic tool, processing the on-line seismic signal received from remote stations. Amplitude data are calculated over 10s long time windows, in frequency bands, 1 Hz wide, between 0.5 and 15 Hz, as well as in the unfiltered continuous signal. Data format is ASCII. Appropriate metadata (such as technical specifications, geographical coordinates of sites, etc.) have also been defined for the three data types, enabling users to perform analysis and characterization of data. All data and metadata are shared with subscriber users in the MED-SUV Project portal.PublishedRome (Italy)4IT. Banche dat