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The San Bartolo lava flow field is the most recent flank eruption occurred at Stromboli volcano about 2 ka ago on the NE flank of the island. Despite its importance in being the most recent example of flank activity outside the barren Sciara del Fuoco slope, where the recent activity concentrated, the eruption duration, its volume, and the sequence of events has not yet been reconstructed. In this paper, we present a new survey of the lava flow field, carried out both on the field and photogrammetric and LIDAR surveys from UASs, in order to estimate the erupted lava volume and to reconstruct the sequence of events and infer a possible duration and impact of the eruption. The analysis of the surveys allowed us to verify the contact with previous lava flow fields, allowing a more precise lateral extension of the lava delta along the coast, as well as an estimation of the thickness and volume, at least for the subaerial portion of the lava flow field. The morphology analysis of the lava flow field allowed us to recognize structures suggesting inflation and then stationing of the lava flow fronts, features indicating a long-lasting eruption and a complex interaction with the sea. Our results can provide a useful scenario should a flank eruption occur in the future, a possibility that was close to happening in 1998, when the ground deformation stations revealed a lateral intrusion in the shallow supply system of the volcano.

The volcanic island of Ischia (southern Italy) represents an interesting challenge as far as both risk analysis and risk management planning (RMP) go; hence, it is detailed here as a study case. We analysed the strengths and weaknesses of the emergency plans brought forward following the August 2017 earthquake, elaborating and revising scientific information, and involving researchers and experts with very different competences and backgrounds (e.g. engineers, architects, geologists, volcanologists, sociologists and information science experts). In particular, the historical evolution of the emergency plans prior to this event was recollected; the social context, on the basis of both literature and new statistical results, was analysed; and the guidelines proposed and/or implemented in other similar contexts in the world were examined. This work analyses and discusses the results, and proposes models that are universally applicable. Indeed, the key factors necessary for a 3E (Effective, Efficient and Effectual) RMP have been identified and described. These factors must characterize the RMP of the island of Ischia – and, in general, of any volcanic island – in order to be able to manage the occurrence of an emergency in the best possible way.

Current EO satellite missions providing imagery in the VIS- TIR region at high spatial resolution offer the possibility to estimate a number of important parameters to monitor volcanic activities at worldwide level. Therefore, space missions contribute in understanding the ongoing phenomena to mitigate the volcanic risk when population and infrastructures are exposed. New hyperspectral and thermal missions which could provide images at high spatial and temporal resolution are under study in cooperation between Space Agencies (NASA, ASI, ESA etc.) and hopefully will improve the monitoring capabilities of active volcanoes in highly populated areas. In the present work we describe several results obtained in the last years by EO satellite missions for the volcanic risk. While the satellite data provide a wide description of scenes, in situ and proximal measurements are crucial to retrieve gas emissions and analyze surface characteristics at very high spatial resolution. Data acquired from drones (UAV) and thermal cameras in volcanic areas are presented and discussed. Moreover, this work shows the need of validation process for satellite products comparing with measurements collected during field campaigns.

The Istituto Nazionale di Geofisica e Vulcanologia (INGV) has developed an interactive application, for educational purposes, in order to make schools aware of the dangers deriving from radon, and in general from harmful gases (gas hazards), near volcanic areas. To raise children awareness on the dangers related to an invisible enemy, often odorless “gases”, is not a simple task. Since our target are children between 11 and 13 years of age, we decided to develop a videogame with the scope of enabling them to learn the most appropriate solutions for identifying/avoiding/managing hazards. The use of a videogame for spreading information on gas hazards makes learning fun and, at the same time, feasible in a historic moment where Covid-19 does not allow for lessons to be physically partaken in a classroom. Furthermore, this type of learning known as “edutainment” is more effective, captivating and meaningful, allowing students to acquire a more concrete and longer remembered knowledge. The videogame, called GioGas, is a single player game running on both Android mobile phone and personal computers. GioGas has been developed using the Role Playing Game Maker MV graphic engine. The engine provides a map editor and several characters allowing for the creation of various biomes, also including the possibility to insert music. From the technical point of view the engine is based on javascript for the events creation and triggers management simplifying porting on mobile and desktop operating systems. The game characters are a INGV researcher, staying in a rented house during his vacation, and an elderly lady that asks for help to understand if her grandchild’s health issues are related to the recent digging of a well nearby the house. The characters move around in the virtual environment in different locations organized in several levels. Through the game, the student will learn the symptoms caused by gases, the instruments and the techniques to identify/measure them and the solutions to adopt to solve the problem. During the game, the researcher will hand out information and the student will choose which solution to apply: this will also stimulate student inclination to problem solving and overview capacities. Each solution will return a result in terms of risk mitigation and a score, from 1 to 3, based on the effectiveness of the identified solution. In the future, to add more stimulating and engaging elements for the student, a multiplayer mode will be developed, giving the students the possibility to challenge themselves.

Research Institutions are tackling the ever so increasing challenge to share the outcomes of scientific research and technological innovations with a forthright method in order to increase involvement of the community. To achieve that aim, the main recipients of the information must be the focus point on which outreach and educational activities concentrate. Standard analysis of visitor’s experiences within informal learning activities can provide useful information on the activity impacts. In fact, evaluating the performance allows to improve the effects, achievements and benefits in the audiences. This research was carried out by analysing quantitative and qualitative studies performed in the occasion of a temporary outreach event, in which visitors were the focal point. Different types of audiences were examined during an Open Day at the Istituto Nazionale di Geofisica e Vulcanologia (INGV)—Italian Institute of Geophysical and Volcanological Research—based in Rome, leading to the results we present in this work. The event was remarkable as it brought together a broad selection of scientific laboratories, exhibition spaces and meetings with researchers, all custom tailored towards the specific audiences. At the end of the event, questionnaires were handed over to the visitors, both young and adults, and to any stakeholder that were present. The answers and the open feedbacks from the visitors have disclosed valuable information on INGV’s audience, and allowed the events organization and contents to be refined and improved. This procedure can most certainly be turned into a methodical system to obtain a general picture of the cognitive and emotional effects on visitors participating in scientific itineraries. The quantitative method used in this research involved analysing the answers in the questionnaires with a statistical approach and was blended with the qualitative method that took into account the visitor’s personal feedback and input. The aftermath of the study allows to pinpoint the main event issues and to take actions aimed to enrich visitor’s satisfaction and experience. In fact, advertising of the events ahead of time, arranging a well designed and implemented online information and booking system in order to better accommodate for the number of visitors, realizing dedicated apps for the each tours, creating a shorter questionnaire for children, and creating standards for questionnaires that would be used in the future.

Geothermal and volcanic systems are prone to gravity-induced slope instability at different scales. Endogenous magmatic, hydrothermal and seismic forcings can significantly modify rock mass rheology and perturb the local stress field and gravitational equilibrium, inducing shallow or slope-scale processes. The island of Ischia, which is part of the Phlegrean Volcanic District (Italy), is a remarkable example of this kind of complex interacting system. This study focuses on monitoring the hydrothermal system located beneath the ongoing slope-scale deformation, which involves Mt Nuovo (the western part of Mt Epomeo) and is a complementary effect of the resurgence of an ancient caldera. Debris and rock avalanches have affected the slopes of this volcanic island, in response to the renewal of volcanic activity and caldera resurgence. Large parts of the corresponding mass-wasting deposits overlay the most active areas of the Ischia hydrothermal system, where ongoing slope-scale gravity-driven deformation owing to a mass rock creep (MRC) process is still evolving. To investigate possible relations between the perturbing shallow hydrothermal system and the MRC process, thermal monitoring of selected groups of fumarolic emissions located in several portions of the deforming sector has been carried out since 2008 on a monthly basis by means of direct (thermal probes) and remote sensing (IR-thermography) techniques. Thermal monitoring of specific fumaroles reveals a peculiar seasonal trend characterized by a delayed inverse correlation with rainy periods and a short-term pulsating response to dry stages. The fumaroles also appear spatially correlated to the presence of MRC-related structures involving volcanic slopes. According to the measured thermal data, a conceptual model of the thermal interactions within the Mt Nuovo slope is provided, framing the potential role of thermal actions in accelerating the deformation process. In this view, possible chain effects, owing to magmatic or hydrothermal renovation, are depicted, delineating the most severe multihazard scenario consisting of an accelerating evolution of the MRC process towards paroxysmal collapse.

The volcanic system of Ischia is characterized by an intense hydrothermal activity, documented since the early 16th century by the study of Iasolino (1588), which represents the first systematic analysis of the thermal springs of the island for therapeutic purposes. Later studies partially contributed to the enhancement of knowledge on the volcanic, hydrogeological and hydrothermal features of the island, highlighting the strong interaction between hydrothermal flowpaths and volcano-tectonic processes . The reconstruction of the hydrothermal system becomes, therefore, a fundamental element for territorial planning, not only in terms of management of the huge water and geothermal resource, but also and above all in a perspective of prevention and mitigation of volcanic risk. Thermal springs, fumaroles and clay deposits due to the hydrothermal alteration of volcanic products testifies for the existence of an active deep hydrothermal system. Commonly, the geochemical characterization of fluids and groundwater has been used for the definition of the origin and structure of hydrothermal systems, when hydrogeological information is incomplete. However, volcanic hydrothermal systems, such as that characterizes the island of Ischia, are particularly difficult to analyze and outline, as the groundwater resources are the result of an articulated and dynamic interaction among meteoric water, sea water and fluids of deep origin. In such cases, the need for an interdisciplinary approach is evident, involving knowledge and research methods ranging from geology to volcanology, geophysics, geochemistry and hydrogeology. With particular reference to the functional and structural representation of the geothermal system of the island of Ischia and the resulting correlations with the volcano-tectonic processes, the examination of previous information highlights the need to update and improve the knowledge on groundwater hydrodynamics and mineralization processes.Therefore, this study represents the result of a strong interdisciplinary action that, starting from the design and implementation of a database on the existing geological/volcanological and hydrogeological information, contributes to highlight the critical issues, defines an operating scheme of the hydro-geo-thermal system of the island of Ischia, and aims at upgrade its hydrogeological, geochemical and volcanic monitoring system, in order to contribute to the mitigation of natural risks.Moreover, this study well fits into the framework of the ongoing researches on volcanic hazard at Ischia and is integrated with the actions planned by the Italian Department of Civil Defense. The knowledge of groundwater dynamics and pathways is of fundamental importance for understanding the water/magma interaction processes in case of re-alimentation of the shallow magmatic system, and the assessment of the possibility of phreatic explosions occurrence.

During the field campaign held on June 2018 at Parco delle Biancane and Sasso Pisano areas, near Grosseto (Italy), we have measured the surface temperature using data acquired by different sensors at different spatial resolutions: Earth Observation (EO) data from the ECOsystem Spaceborne Thermal Radiometer Experiment on Space Station (ECOSTRESS), Hyperspectral Thermal Emission Spectrometer (HyTES) airborne imaging data and thermal images acquired by the FlyBit drone. ECOSTRESS has five spectral bands in the range 8-12.5 μm and pixel size resolution (at nadir) of 69x38 m (2 pixels in cross track and 1 pixel in down track); HyTES is an airborne imaging spectrometer having 256 spectral channels in the range 7.5-12 μm and high spatial resolution (0.8 m for the June campaign); VUE PRO-R mounted on FlyBit drone acquires in the range 7.5-13.5 µm with a spatial resolution depending on the flight altitude (in this work the pixel size is about 0.25 m). In addition, the Sony Alpha 600 visible camera was mounted on the FlyBit drone to acquire a very high resolution optical images over the test site. Our goal is to test the possibility to integrate data at different observation scales and to use the proximal measurements to better understand the thermal structure of test sites, also related to the area morphology and to validate the methodology for estimating the surface temperature by using EO data.

The purpose of this study is to analyze the surface temperature and the distribution of thermal signatures on Tuscany’s geothermal districts using data obtained through three separate surveys via satellite and an unmanned aerial vehicle (UAV). The analysis considers the highest available spatial resolution ranging from hundreds of meters per pixel of the satellite thermal images and the tenths/hundreds of centimeters per pixel of the thermal images acquired by the UAV. The surface temperature maps obtained by satellite data acquired at suitable spatial resolution and the thermal measurements obtained by the thermal camera installed on the UAV were orthorectified and geocoded. This allowed, for example, following the evolution of thermal anomalies, which may represent a modification of the current state of the geothermal field and a possible hazard for both the population and industrial assets. Here, we show the results obtained in three field campaigns during which the simultaneous acquisition of Landsat 8 satellite and UAV (FlyBit octocopter, IDS, Rome, Italy) thermal data were analyzed. By removing the atmosphere contribution from Landsat 8 data, we have produced three surface temperature maps that are compared with the ground field measurements and the surface temperature maps elaborated by FLIR VUE PRO-R on the UAV.

On 21 August 2017, a shallow earthquake of Md 4.0 struck the CasamicciolaTerme village in the north of Ischia volcanic island (Italy). It caused two fatalities and heavy damage in a restricted area of a few square kilometers. Casamicciola Terme has been recurrently destroyed in the last centuries by similar volcano-tectonic earthquakes (1762, 1767, 1796, 1828, 1881, and 1883). After the catastrophic 1883 Casamicciola event (2343 casualties), this is the first heavy damaging earthquake at Ischia that provides, for the first time, the opportunity of integrating historical seismicity, macroseismic observations, instrumental information, and detailed mapping of coseismic geological effects. Soon after the 2017 mainshock we surveyed the epicentral area to collect data on the coseismic ground effects, recording more than 100 geological field observations. Mapped effects define a belt which closely follows the trace of the Casamicciola E-W-trending normal fault system, bounding the northern slope of Mt. Epomeo, previously known as a Latest Pleistocene to Holocene normal fault with a slip rate of ~3:0 cm=yr. We found significant evidence for coseismic surface faulting, testified by a main alignment of ruptures for a 2 km end-to-end length and normal dip-slip displacement of 1-3 cm. The geometry and regularity of the structural pattern, together with constant kinematics of the coseismic ruptures with the north side down, strongly suggest a primary tectonic origin for the mapped ruptures and strongly supports an E-W normal-faulting focal mechanism for the 2017 Casamicciola earthquake.Macroseismic information supports the notion that previous historical events also had a similar style of faulting.

Quiescent volcanoes dissipate a large part of their thermal energy through hot soils and ground degassing mainly in restricted areas called Diffuse Degassing Structures. La Solfatara crater represents the main spot of thermal release for the Campi Flegrei volcano (Italy) despite its reduced dimensions with regards to the whole caldera. The purpose of this study was to develop a method to measure thermal energy release extrapolating it from the ground surface temperature. We used imaging from thermal cameras at short distances (1 m) to obtain a mapping of areas with thermal anomalies and a measure of their temperatures. We built a conceptual model of the energy release from the ground to atmosphere, which well fits the experimental data taken in the La Solfatara crater. Using our model and data, we could estimate the average heat flux in a portion of the crater as q a v g = 220 ± 40 W / m 2 , compatible with other measurements in literature.

This paper was partially supported by a grant to S.C. (Project INGV-DPC Paroxysm V2/03, 2008–2010) funded by the Istituto Nazionale di Geofisica e Vulcanologia and by the Italian Civil Protection.

As far as the European continent, Region Campania in Southern Italy presents an almost unique combination - in terms of both variety and intensity-of potential risks for the residents: this densely populated area is actually most notably exposed to hydrogeological (flood and landslides), seismic, volcanic hazards In such a setting, alongside with an up-to-date scientific approach to risks analysis and the constant update of emergency plans, it is of paramount importance that a “risk awareness culture” should be developed by the residents. In order to maximize the effectiveness of the communication campaigns to support and improve such a culture, a study of risk perception has been carried out in 12 municipalities and 2 territorial unions of Campania Region. Different areas have been examined, the overall exposure of each almost always being characterised by a prevalent specific risk: seismic, volcanic, hydrogeological. The results of this surveys show that the historical memory has a crucial role on the hazards perception. It's also worth of noting that few communities consider that they have been sufficiently well-informed by civil protection agencies and/or authorities about the natural hazards specific to their area and the practical procedures for evacuation. To overcome these deficiencies emergency plans should be designed, developed and practised through the collaboration of all key stakeholders, from civil protection authorities to the residents communities.

La relazione scientifica riguarda i risultati derivanti dalle prime acquisizioni geofisiche (ERT, MASW, indagini sismiche a riflessione, misure di rumore sismico, Array) condotte a seguito del sisma del 21 agosto 2017 occorso sull'Isola di Ischia. Inoltre la relazione è corredata da sette carte geo-tematiche (carta geolitologica, carte geologico-tecniche, carte delle frequenze fondamentali, carte delle indagini) relative ai territori comunali di Casamicciola Terme, Lacco Ameno, Forio (NA). Vengono anche presentati i risultati preliminari di modellazioni numeriche bidimensionali di risposta sismica locale, relativi alla zona rossa di Casamicciola Terme.

A set of analogue models has been carried out to understand the role of an asymmetric magma chamber on the resurgence-related deformation of a previously deformed crustal sector. The results are then compared with those of similar experiments, previously performed using a symmetric magma chamber. Two lines of experiments were performed to simulate resurgence in an area with a simple graben-like structure and resurgence in a caldera that collapsed within the previously generated graben-like structure. On the basis of commonly accepted scaling laws, we used dry-quartz sand to simulate the brittle behaviour of the crust and Newtonian silicone to simulate the ductile behaviour of the intruding magma. An asymmetric shape of the magma chamber was simulated by moulding the upper surface of the silicone. The resulting empty space was then filled with sand. The results of the asymmetric-resurgence experiments are similar to those obtained with symmetrically shaped silicone. In the sample with a simple graben-like structure, resurgence occurs through the formation of a discrete number of differentially displaced blocks. The most uplifted portion of the deformed depression floor is affected by newly formed, high-angle, inward-dipping reverse ring-faults. The least uplifted portion of the caldera is affected by normal faults with similar orientation, either newly formed or resulting from reactivation of the pre-existing graben faults. This asymmetric block resurgence is also observed in experiments performed with a previous caldera collapse. In this case, the caldera-collapse-related reverse ring-fault is completely erased along the shortened side, and enhances the effect of the extensional faults on the opposite side, so facilitating the intrusion of the silicone. The most uplifted sector, due to an asymmetrically shaped intrusion, is always in correspondence of the thickest overburden. These results suggest that the stress field induced by resurgence is likely dictated by the geometry of the intruding magma body, and the related deformation is partially controlled by pre-existing tectonic and/or volcano-tectonic structures.

Ischia is an active volcanic island in the Gulf of Naples whose history has been dominated by a caldera-forming eruption (ca. 55 ka) and resurgence phenomena that have affected the caldera floor and generated a net uplift of about 900 m since 33 ka. The results of new geomorphological, stratigraphical and textural investigations of the products of gravitational movements triggered by volcano-tectonic events have been combined with the information arising from a reinterpretation of historical chronicles on natural phenomena such as earthquakes, ground deformation, gravitational movements and volcanic eruptions. The combined interpretation of all these data shows that gravitational movements, coeval to volcanic activity and uplift events related to the long-lasting resurgence, have affected the highly fractured marginal portions of the most uplifted Mt. Epomeo blocks. Such movements, mostly occurring since 3 ka, include debris avalanches; large debris flows (lahars); smaller mass movements (rock falls, slumps, debris and rock slides, and small debris flows); and deep-seated gravitational slope deformation. The occurrence of submarine deposits linked with subaerial deposits of the most voluminous mass movements clearly shows that the debris avalanches impacted on the sea. The obtained results corroborate the hypothesis that the behaviour of the Ischia volcano is based on an intimate interplay among magmatism, resurgence dynamics, fault generation, seismicity, slope oversteepening and instability, and eruptions. They also highlight that volcano-tectonically triggered mass movements are a potentially hazardous phenomena that have to be taken into account in any attempt to assess volcanic and related hazards at Ischia. Furthermore, the largest mass movements could also flow into the sea, generating tsunami waves that could impact on the island’s coast as well as on the neighbouring and densely inhabited coast of the Neapolitan area.

The results of a detailed stratigraphic study, carried out in the areas located to the east and south-west of Mt. Epomeo at Ischia, are presented and compared with those of previous geological, archaeological and historical investigations to show the relationships among caldera resurgence, volcanism and slope instability in the past 5.5 ka. Resurgence at Ischia began at about 30 ka B.P. and occurred through intermittent uplifting and tectonic quietness phases. During the past 5.5 ka reactivation of faults and related volcanic activity was accompanied by emplacement of deposits generated by surface gravitational movements. These deposits were generated in four main phases, dated between 5.5 and 2.9 ka, around 2.9 ka, between 2.6 and 2.3 ka, and between 2.3 and 1.9 ka, respectively. Deposits formed by gravitational movements preceded and followed the emplacement of volcanic rocks, testifying that slope instability was induced by vertical movements, which also activated and/or reactivated faults and fractures that fed volcanism. The results of this study therefore suggest that, although slope failure can occur as a consequence of a variety of factors, resurgence has to be considered a factor inducing a particularly intense slope instability. Resurgence is accompanied by activation of faults and renewal of volcanism, causing oversteepening of the slopes and generating seismicity that could trigger surface gravitational movements. Furthermore, the availability of large amount of loose material, rapidly accumulated along the slopes during eruptions, favors landslide generation.

Fumarolic fluid compositions and diffuse soil emissions of hydrothermal fluids of the Donna Rachele area (0.86 km 2 , western flank of Mt. Epomeo, Ischia Island) have been studied in order to develop a conceptual geochemical model of the hydrothermal system. The degassing area was mapped and the total release of hydrothermal gas and heat associated with the diffuse emission of hydrothermal fluids was estimated. A mesostructural study was carried out in order to investigate the relations between the brittle structures and the main pathways of the uprising vapor. The fumarolic compositions are typical of hydrothermal fluids and water (>99%) represents the major component. All gas species in the H 2 O–H 2 –CO–CH 4 –CO 2 –H 2 S system are close to equilibrium concentrations at temperatures of ∼300°C and at redox conditions slightly more oxidizing than expected. The compositions of the Donna Rachele fumarolic gas approach the pure liquid equilibrium composition. This indicates a high fraction of separated vapor and suggests the presence of a highly energetic hydrothermal system at depth. The pure liquid equilibrium compositions of the Donna Rachele fumaroles, along with the historical records of shallow seismicity, the ‘explosion’ of a well in 1995, the occurrence of intense acoustic phenomena and of shallow wells discharging vapor indicate that the internal pressure of the hydrothermal system is occasionally larger than the hydrostatic pressure. To quantify the energy dissipated in the Donna Rachele area by the emission of fumarolic fluids, the hydrothermal diffuse degassing was studied by means of 336 soil CO 2 flux measurements. The highest CO 2 fluxes were measured in hydrothermally altered areas along the faults that border Mt. Epomeo. Structural data indicate that the vapor rises up along NW–SE striking normal faults related to gravity-induced stresses and affecting highly fractured lavas. The older faults, which are related to the Mt. Epomeo resurgence, act as a permeability barrier and bound the Donna Rachele diffuse degassing structure. The total hydrothermal CO 2 output was estimated to be ∼9 t d −1 . Assuming that the H 2 O/CO 2 ratio of the fluids that feed the diffuse degassing is the same as that of fumarolic effluents, the calculated heat flux is ∼40 MW. This value, which represents an important energy release, is only a part of the total thermal energy release of Ischia, where other fumarolic areas occur. The results obtained at Ischia indicate the importance of thermal energy released by diffuse degassing structures in the energy balance of quiescent volcanoes. Values of the thermal energy release from the Ischia hydrothermal system are comparable with those estimated on other quiescent volcanoes.

Stromboli is known for its mild, persistent explosive activity from the vents located within the summit crater depression at the uppermost part of the Sciara del Fuoco (SdF) depression. Effusive activity (lava flows) at this volcano normally occurs every 5–15 years, involving often the opening of eruptive fissures along the SdF, and more rarely overflows from the summit crater. Between the end of the 2007 effusive eruption and December 2012, the number of lava flows inside and outside the crater depression has increased significantly, reaching a total of 28, with an average of 4.8 episodes per year. An open question is why this activity has become so frequent during the last 6 years and was quite rare before. In this paper, we describe this exceptional activity and propose an interpretation based on the structural state of the volcano, changed after the 2002–2003 and even more after the 2007 flank effusive eruption. We use images from the Stromboli fixed cameras network, as well as ground photos, plume SO2 and CO2 fluxes released by the summit crater, and continuous fumarole temperature recording, to unravel the interplay between magma supply, structural and morphology changes, and lava flow output. Our results might help forecast the future behaviour and hazard at Stromboli and might be applicable to other open-conduit volcanoes.

Ischia is the emergent top of a large volcanic complex that rises more than 1,000 m above the sea floor, at the north-western end of the Gulf of Naples. Caldera resurgence in the central part of the island has resulted in the formation of differentially displaced blocks, among which Mt. Epomeo (787 m a.s.l.) is the most uplifted. Deformation and slope instability have been recognised as common features induced by a block resurgence mechanism that causes uplift and favours gravitational loading and flank failure. The Monte Nuovo block, a topographic high on the north-western flank of Mt. Epomeo, has recently been interpreted as a block affected by deep-seated gravitational slope deformation. This block may undergo a catastrophic failure in the case of renewal of magmatic activity. This paper investigates the potential failure of the Monte Nuovo block as a rockslide-debris avalanche, the consequent tsunami generation and wave propagation, and discusses the catastrophic effects of such an event. Mobilization-prone volume has been estimated at about 160·106 m3 and would move from a maximum elevation of 400 m a.s.l. The landslide itself would sweep away a densely populated territory as large as 3.5 km2. The highest waves generated by the tsunami, on which this paper is mainly focussed, would hit the northern and western shores of Ischia. However, the high coast would prevent inundation and limit devastation to beaches, harbours and surrounding areas. Most of the tsunami energy would head towards the north-east, hitting the Campania coast. Severe inundation would affect an area of up to 20 km2 around the mouth of the Volturno river, including the urban area of Castel Volturno. In contrast, less energy would travel towards the south, and the Gulf of Naples would be perturbed by long persisting waves of limited damaging potential.

The Agnano–Monte Spina tephra (AMST), dated at 4100 years BP by 40 Ar / 39 Ar and 14 C AMS techniques, is the product of the highest-magnitude eruption in the Campi Flegrei caldera (CFc) during its last epoch of activity (4800–3800 years BP). The sequence alternates magmatic and phreatomagmatic pyroclastic-fallout, -flow and -surge beds and bedsets. Two main pumice-fallout deposits with variable easterly-to-northeasterly dispersal axes are about 10 cm thick at 42 km from the vent area. High particle concentration pyroclastic currents were confined to the caldera depression; lower concentration flows overtopped the morphological boundary of the caldera and traveled at least 15 km over the surrounding plain. The unit is subdivided into six members, named A through F in stratigraphic sequence, based upon their sedimentological characteristics. Isopachs and isopleths maps suggest a vent location in the Agnano plain. A volcano-tectonic collapse begun during the course of the eruption, took place along the faults of the northeastern sector of the resurgent block within the CFc, and generated the Agnano plain. The early erupted trachytic magma had a homogeneous alkali–trachytic composition, whereas later-erupted magma shows small-scale hetereogeneities. Trace elements and Sr-isotope compositions, indicate that two isotopically distinct magmas, one alkali–trachytic and the other trachytic, were tapped and partially mixed during the eruption. The small volume (1.2 km3 DRE) of erupted magma and the structural position of the vent suggest that the eruption was fed by a dyke intruded along a normal fault in the sector of the resurgent block under a tensional stress regime.

[1] On 10 September 2005 at 1711 LT (1511 UT) a loud boom was heard on the Ischia island. A clear seismic signal was also recorded by the seismic monitoring network of the Neapolitan volcanic areas (Ischia, Campi Flegrei, and Mount Vesuvius) and on a regional station (Mount Massico). On the basis of the seismic recordings and on acoustic phenomena reports, we relate this event to the atmospheric explosion (airburst) of a bolide about 15 km SW of Ischia at an elevation of about 11.5 km. The location has been obtained through nonlinear traveltime inversion in a realistic atmospheric model including wind effects. We show, using statistical estimators, how the traveltime pattern is due to both atmospheric winds and the bolide trajectory. Using the same reasoning we discard a human origin (supersonic jet or sea-air missile). In addition, we also propose a new algorithm for fast acoustic traveltime computation for a supersonic moving source.

The structure and shape of collapses and resurgences is often controlled by pre-existing discontinuities, such as normal faults in rift zones. In order to study the role of extensional structures on collapse and resurgence, we used analogue models. Dry sand simulated the brittle crust; silicone, located at the base of the sand-pack, simulated magma. In the experiments, regional extension pre-dated collapse or resurgence, forming normal faults in a graben-like structure; the graben was filled with additional sand, simulating post-rift deposits. A piston then moved the silicone downward or upward, inducing collapse or resurgence within the previously deformed sand. The collapses showed an ellipticity (length of minor axis/length of major axis) between 0.8 and 0.9, with the major axis parallel to the extension direction. The partial reactivation of the pre-existing normal faults was observed during the development of the caldera reverse faults, which, conversely to what was expected (from experiments without pre-existing extension), became partly inward dipping. Resurgence showed an elongation of the uplifted part, with the main axis perpendicular to the extension direction. At depth, pre-existing normal faults were partly reactivated by the reverse faults formed during resurgence; these locally became outward dipping normal faults. A total reactivation of pre-existing faults was also observed during resurgence. The experiments suggest that the observed elongation of calderas and resurgences is the result of the reactivation of pre-existing structures during differential uplift. Such a reactivation is mainly related to the loss in the coefficient of friction of the sand. The results suggest that elliptic calderas and resurgences in nature may develop even from circular magma chambers.

Accepted for publication in (Geophysical Research Letters). Copyright (2009) American Geophysical Union.