Self-Fluidization of Fastly-Moving Granular Gravity Currents with Implication on Pyroclastic Flows

The fast motion of gravity currents of group A granular solids is studied with a focus on the dynamical structure of the frontal zone. The frontal zone of the current is “immobilized” and observed in a fixed frame of reference by letting the current flow inside a rotary drum, big enough to make curvature effects negligible. The establishment of a variety of flow regimes, including intermittent avalanching, periodic “plunging breaking” and permanent fluidization of the granular solids in the frontal zone, can be related to flow conditions and to the nature of the granular solids

A multi-methodological approach to record dynamics and timescales of the plumbing system of Zaro (Ischia Island, Italy)

Determining the time spans of processes related to the assembly of eruptible magma at active volcanoes is fundamental to understand magma chamber dynamics and assess volcanic hazard. This information can be recorded in the chemical zoning of crystals. Nevertheless, this kind of study is still poorly employed for the active volcanoes of the Neapolitan area (Southern Italy), in particular, for Ischia island where the risk is extremely high and this information can provide the basis for probabilistic volcanic hazard assessment. For these reasons, we acquired chemical composition on clinopyroxene crystals erupted at Ischia during the Zaro eruption (6.6 ± 2.2 ka) and performed numerical simulations of the input of mafic magma into a trachytic reservoir, in order to investigate various aspects of pre-eruptive dynamics occurring at different timescales. This event emplaced a ~ 0.1 km3 lava complex, in which the main trachytic lava flows host abundant mafic to felsic enclaves. Previous petrological investigation suggested that mafic magma(s) mixed/mingled with a trachytic one, before the eruption. In this work, the clinopyroxene zoning patterns depict the growth of crystals in different magmatic environments, recording sequential changes occurred in the plumbing system before the eruption. The evolution of the plumbing system involved a hierarchy of timescales: a few hours for magma mingling caused by mafic recharge(s) and likely occurred multiple times over a decade during which a dominant magmatic environment was sustained before the eruption. Such timescales must be considered in volcanic hazard assessment at Ischia and similar active volcanoes in densely populated areas

Array and spectral ratio techniques applied to seismic noise to investigate the Campi Flegrei (Italy) subsoil structure at different scales

Abstract. The purpose of this work is to study the subsoil structure of the Campi Flegrei area using both spectral ratios and array techniques applied to seismic noise. We have estimated the dispersion curves of Rayleigh waves by applying the Frequency–Wavenumber (f–k hereinafter) and Modified Spatial Autocorrelation (MSPAC) techniques to the seismic noise recorded by the underground short period seismic Array "ARF", by the broadband stations of the UNREST experiment and by the broadband stations of the seismic monitoring network of INGV – Osservatorio Vesuviano. We have performed the inversion of a dispersion curve (obtained averaging the f–k and MSPAC dispersion curves of seismic noise and single phase velocity values of coherent transient signals) jointly with the H∕V spectral ratio of the broadband station CELG, to obtain a shear wave velocity model up to 2000 m depth. The best-fit model obtained is in a good agreement with the stratigraphic information available in the area coming from shallow boreholes and deep wells drilled for geothermal exploration. In active volcanic areas, such as Campi Flegrei, the definition of the velocity model is a crucial issue to characterize the physical parameters of the medium. Generally, a high quality characterization of the medium properties helps to separate the contributions of the volcanic source, path and site in the geophysical observables. Therefore, monitoring possible variations in time of such properties in general can help to recognize anomalies due to the volcano dynamics, i.e. fluid migration connected to the volcanic activity

Experimental study for evaluation of a suitable ground displacement monitoring system: Pilot hole Campi Flegrei Deep Drilling Project case

The paper presents an experimental study carried out in 2012 during the drilling activity for a pilot hole performed in the framework of the Campi Flegrei Deep Drilling Project. A monitoring network has been installed to test and choose a suitable ground deformation system for the subsequent deep drilling of about 3.5 km in the Campi Flegrei Caldera (Italy). We describe the seismic network installed to characterize the structure of the pilot hole area and the ground deformation monitoring system chosen for the small drilling area. Data analysis and results obtained indicate that Total Station is a suitable tool for this case.Published4V. Dinamica dei processi pre-eruttiviN/A or not JC

Climate fluctuations and human impact during the late Holocene in a multi-proxy marine record from the Gulf of Gaeta (Tyrrhenian Sea, central Italy)

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Deltaic and Coastal Sediments as Recorders of Mediterranean Regional Climate and Human Impact Over the Past Three Millennia

This work was financially supported by the MISTRALS/PaleoMex program and by the Project of Strategic Interest NextData PNR 2011–2013 (www. nextdataproject.it). Lionel Savignan is thanked for his participation in the biomarker analysis. Radiocarbon datings for core KESC9-14 have been funded by Institut Carnot Ifremer-EDROME (grant A0811101). We also thank the Holocene North-Atlantic Gyres and Mediterranean Overturning dynamic through Climate Changes (HAMOC) project for financial support. The biomarker data presented here are available in the supporting information.Peer reviewedPublisher PD

Preliminary analysis of site effects in the Ischia island: new insights from md 4.0 earthquake of 21 august 2017 and seismic noise data

On August 21, 2017, at 18:57 UTC, an earthquake of MD 4.0 occurred in Casamicciola, district of Ischia island. The damage caused by the earthquake was massive, with two victims and several buildings collapsed, and circumscribed to the areas of uptown Casamicciola, particularly in the Piazza Maio-La Rita area, and in a small area, called Fango, in Lacco Ameno. Medium and minor damages occurred in Piazza Bagni, in the area around the town hall of Casamicciola and in the Sentinella area. Even assuming the poor quality constructions and/or not in compliance with the anti-seismic regulations, such a level of damage has induced the scientific community to analyse the effects of local site amplifications, that usually are not negligible in volcanic areas. As a matter of fact the seismic station IOCA, located very close to the high damage areas, recorded a peak ground acceleration (PGA) of 2.6 m/s2. This paper is aimed to study the possible site amplification in the areas heavily affected by the August 21 earthquake in order to better understand the causes of these macroseismic effects and high damage levels already observed in the past.PublishedCentro Congressi della Stazione Marittima, Trieste, Italy6V. Pericolosità vulcanica e contributi alla stima del rischi

The Borehole Experiment: Investigation of Cortical Structures Through 3D Array Techniques

Over the last few years it is growing the need to monitor the volcanic activity with modern technology in order to mitigate volcanic hazard through the detection of any possible precursor phenomena. The use of high performance seismic stations, such as borehole instruments, may increase the signal to noise ratio (SNR), improving the capability to detect very small signals. Over the past 40 years much attention has been given to the use of seismic arrays to measure the slowness vector of coherent signals. The main advantage of seismic arrays consists in their ability to detect weak or emergent signals, and to allow for an effective noise reduction through multichannel waveform stacking. A reliable prediction of the ray-path back-propagated from the recording site to the source is strongly limited by the poor knowledge of the local shallow velocity structure. Usually in volcanic environments the propagation of seismic signals through the shallow layers is strongly affected by lateral heterogeneity, attenuation, scattering, and interaction with the free surface. Driven by these motivations, on May 2014, in collaboration with the colleagues of Osservatorio Vesuviano (INGV), we deployed a 3D seismic array in the area where the borehole seismic station called Pozzo Pitarrone is installed at a depth of about 130 meters. This will improve our knowledge about: • the structure of the top layer and its relationship with geology; • analysis of the signal to noise ratio (SNR) of volcanic signals as a function of frequency; • study of seismic ray-path deformation caused by the interaction of the seismic waves with the free surface; • evaluation of the attenuation of the seismic signals correlated with the volcanic activity. The results of these analyses will improve the general knowledge of wave propagation in the shallow layers and will give a new contribution to the seismic monitoring of Etna volcano.PublishedNicolosi (Catania), Italy1T. Struttura della Terr

The italian quaternary volcanism

The peninsular and insular Italy are punctuated by Quaternary volcanoes and their rocks constitute an important aliquot of the Italian Quaternary sedimentary successions. Also away from volcanoes themselves, volcanic ash layers are a common and frequent feature of the Quaternary records, which provide us with potential relevant stratigraphic and chronological markers at service of a wide array of the Quaternary science issues. In this paper, a broad representation of the Italian volcano logical community has joined to provide an updated comprehensive state of art of the Italian Quaternary volcanism. The eruptive history, style and dynamics and, in some cases, the hazard assessment of about thirty Quaternary volcanoes, from the north ernmost Mt. Amiata, in Tuscany, to the southernmost Pantelleria and Linosa, in Sicily Channel, are here reviewed in the light of the substantial improving of the methodological approaches and the overall knowledge achieved in the last decades in the vol canological field study. We hope that the present review can represent a useful and agile document summarising the knowledege on the Italian volcanism at the service of the Quaternary community operating in central Mediterranean area

Il monitoraggio sismico dei vulcani attivi della Campania: rete sismica ed analisi dei dati. (Luglio-Dicembre 2001

La Rete Sismica dell’Osservatorio Vesuviano (RSOV) è una rete regionale costituita da stazioni sismiche analogiche a corto periodo e stazioni digitali a larga banda con trasmissione continua dei segnali al Centro di Acquisizione (Fig. 1). La Rete è progettata per il monitoraggio delle aree vulcaniche attive della Campania (Vesuvio, Campi Flegrei, Ischia) e fornisce informazioni relative alla sismicità a scala regionale rilevata dalla Rete Sismica Nazionale Centralizzata (INGV – Centro Nazionale per il Monitoraggio della Sismicità). Il miglioramento e la standardizzazione della Rete iniziato nella prima metà del 2000 è continuato nel 2001 con la ristrutturazione di alcune stazioni (SFT, HR9, OTV, SSB, SMC, SOR) e la conversione a tre componenti di due stazioni dell’area vesuviana (BKE e CPV). Particolare attenzione è stata posta nel miglioramento dell’accoppiamento sismometrobasamento al fine di migliorare il rapporto segnale-rumore, comunque elevato a quasi tutte le stazioni a causa dell’alto grado di urbanizzazione delle aree monitorate. E’ stata completata, inoltre, la ristrutturazione del Ponte Radio Centralizzato posto presso la sede di Via Manzoni. Questa operazione ha comportato la sostituzione di tutti gli apparati radio riceventi, obsoleti o inadeguati, e la ridistribuzione del sistema delle antenne di ricezione. Futuri miglioramenti ed espansioni della Rete sono inseriti nel Piano Triennale delle attività dell’I.N.G.V. e prevedono la conversione in larga banda di alcune stazioni analogiche e la ridondanza dei sistemi di trasmissione (telemetria UHF e telefonica digitale) per garantire la continuità dell’acquisizione dei segnali.INGV Sezione di NApoli "Osservatorio Vesuviano"Published1IT. Reti di monitoraggio e sorveglianz