Recent publications
On 21 August 2017, a Mw 3.9 earthquake struck the island of Ischia, causing two casualties and significant damage in the village of Casamicciola Terme and its surroundings. The earthquake was recorded by the local INGV-OV seismic network, and represents the first relevant instrumentally recorded earthquake on the island. However, it is not possible to perform a statistical analysis based on past recordings, which forms the basis of the Ground Motion Model at a local scale. The numerical simulations can help overcome this problem. Here, we first analysed the low magnitude seismicity of the island and focused on estimating the seismic attenuation and average static stress drop through spectral inversion analysis. We then used a stochastic finite-fault approach considering two source models to simulate the Casamicciola earthquake’s strong ground motion by also taking into account the site effect at the IOCA station. The numerical simulations were also extended to the localities for which observed macroseismic intensity values are available. The simulated peak ground motions, converted into intensities through empirical relationships, are somewhat higher than the observed values for both source configurations, suggesting that the regional dependence between intensity and peak ground motion cannot be overlooked. Future investigations should be undertaken to improve seismic hazard assessment at a local scale. Conversely, synthetic PGAs and PGVs show a satisfactory match with the values predicted by the generic GMM calibrated for volcanic areas in Italy. The results underscore the importance of region-specific GMMs for reliable seismic scenarios.
An intense surge in the equatorial electron temperature (Te) at sunrise, known as the morning Te overshoot, has been one of the defining ionospheric features since its discovery early in the Space Age. Despite decades of study, the behavior of the morning overshoot during geomagnetic storms remains poorly understood. We report a two-stage response of the morning Te overshoot to geomagnetic activity, uncovered by a neural network model. Electron temperatures show an initial enhancement during the storm’s main phase, followed by a drastic depletion exceeding 1000 K and disappearance of the overshoot in the recovery phase. This two-phase change aligns with the early influence of westward prompt penetration electric field, overtaken by the development of the eastward disturbance dynamo later in the storm. These electric field changes affect vertical plasma drifts that redistribute electron densities, modifying ionospheric cooling rates. Our findings provide new insights into the dynamics of one of the most widely studied ionospheric features and showcase the potential of new-generation digital twin models of near-Earth space environment to reveal previously unrecognized physical patterns.
Since early 2021, peculiar Volcano-Tectonic (VT) seismic sequences with very short inter-event times have become increasingly frequent and evident in the Campi Flegrei caldera (Italy), which has been experiencing a long-term unrest since 2005. During the same period the ground deformation (uplift), seismicity and gas emission that characterize the current unrest showed an acceleration. Within this type of seismic sequence, we identify burst-like swarms, characterized by inter-event times so short that they are often not easily recognizable. Here we show that these sequences are located in an area encompassing the main hydrothermal field and a zone affected by a geodetic anomaly (a region that uplifts less rapidly than the surroundings), which became evident in 2021. This type of seismicity has been associated with phreatic explosions and critical phases of unrest in other volcanoes and currently characterizes the state of activity of Campi Flegrei caldera.
This study provides insights into the tectonic evolution of the normal Mt Morrone Fault System (MMFS) in Central Italy and highlights the utility of multidisciplinary approaches in reconstructing the seismic history of dormant fault systems. The MMFS comprises two parallel normal faults that traverse the western slope of Mt. Morrone, and although the system can produce M > 6 earthquakes, it has been aseismic in post Roman times. Here, we combine geochemical analysis of carbonate fault‐scarp samples with new structural fault data and Lidar‐based topographic analysis to provide new constraints on fault geometries and kinematics, the paleo‐earthquake history of MMFS since the Last Glacial Maximum and its slip rates. Structural analysis reveals kinematic similarities between the two parallel strands, reflecting their response to the same stress regime. Rare Earth Elements analyses on 53 limestone samples reveal a minimum of eight concentration fluctuations upscarp, here interpreted as tectonic exhumation of the fault scarp due to post LGM earthquakes. Slip per event ranges from 30 to 110 cm typical of earthquakes with 6.3 ≤ M ≤ 6.8. Lidar analysis reveals triangular slip profiles on both fault strands. We estimate that an earthquake with an average M = 6.5–6.6 would have a recurrence interval of ∼2,125 ± 125 years. Slip rates were calculated to be 0.5–0.65 mm/yr on the lower and 0.65–0.7 mm/yr on the upper fault strand, with the combined system having slip rates of 0.62–0.69 mm/yr. Our findings indicate that both strands of the MMFS are active and accumulate slip interdependently, a finding that is critical for seismic hazard assessment.
This analysis of the impact of geomagnetic storms on the Thermosphere-Ionosphere system provides critical insights into the complex interplay between geomagnetic activity and the upper atmosphere dynamics. On February 3, 2022, SpaceX launched 49 Starlink satellites into orbits at altitudes ranging between 210 and 320 km. Unfortunately, 38 of these satellites were lost due to the effects of two moderate geomagnetic storms, which caused a significant increase in neutral density in the thermosphere, resulting in higher atmospheric drag. To study the impact of these geomagnetic storms on the Thermosphere-Ionosphere system, F-layer Ne(h) profiles from ground-based ionosondes, located in different longitudinal sectors of both hemispheres, along with Swarm-C neutral density observations, were analyzed using an original method called THERION (THERmospheric parameters from IONosonde observations). The analysis revealed that during the daytime in mid-latitude regions, the thermosphere exhibited relatively small neutral density perturbations of less than 50% at an altitude of 250 km. However, significant disturbances in thermospheric and ionospheric parameters were identified in the longitudinal sectors over America and Australia. In the Northern Hemisphere’s winter, the largest increase in atomic oxygen [O] was revealed, ranging between 30% and 50%, which significantly contributed to the rise in neutral density at 250 km (ρ250). This seasonal increase in [O] was a key factor driving the observed neutral density changes. Conversely, in the summer hemisphere, atomic oxygen [O] decreased by 20–40%, reducing its contribution to neutral density. Instead, the rise in ρ250 was primarily attributed to an increase in molecular nitrogen [N2], which was driven by elevated neutral temperatures (Tex) caused by the geomagnetic storms. In the Northern Hemisphere’s winter, the combined effects of atomic oxygen [O] downwelling and an increase in molecular nitrogen [N2], driven by higher neutral temperatures (Tex), acted in phase. This synergy resulted in a 35–45% rise in neutral density at 250 km. In contrast, during the Southern Hemisphere’s summer, the opposing effects of [O] (which decreased) and [N2] (which increased) largely cancelled each other out. As a result, the overall impact on ρ250 was minimized, showing limited changes in neutral density. This contrast illustrates the seasonal dependence of thermospheric composition and temperature responses to geomagnetic disturbances. The European longitudinal sector exhibited behavior similar to the American longitudinal sector but with less intensity. Here, a 16–35% storm-time increase in neutral density at 250 km was primarily driven by a rise in atomic oxygen [O]. In the winter Japanese sector, neutral density perturbations were modest, with increases of less than 21%, primarily attributed to elevated neutral temperatures (Tex). These findings indicate that while the overall impact of the two February 2022 geomagnetic storms on the Thermosphere-Ionosphere system was moderate, it was significant enough to cause the loss of 38 satellites. This underscores the critical need for continuous monitoring of the thermosphere to better predict and mitigate the effects of geomagnetic activity on satellite operations.
Explosive volcanic eruptions inject volcanic particles, such as ash and water vapor, into the atmosphere. Ice enriched volcanic clouds can hide the presence of silicate particles, intensifying the fatal risks for aviation. In this scenario, satellite monitoring systems play a key role in volcanic hazard mitigation. Thanks to the full disk perspective over the Pacific Ocean, the GOES‐17 geostationary satellite observed the 15 January 2022 Hunga Tonga‐Hunga Ha'apai hydromagmatic eruption. The explosive activity produced two volcanic clouds dispersing at different altitudes. In this work, we first focus on the altitude estimates of the two volcanic clouds, by means of volcanic cloud speed and wind components. Next, we study how the fine ash (< 64 μm diameter) total mass in atmosphere varies depending on the assumed fraction of ash and ice in an aggregate. Based on our estimates, the upper volcanic cloud disperses between 27.35 ± 3.01 and 29.13 ± 3.20 km altitude; the lower cloud between 14.02 ± 1.54 and 14.8 ± 1.63 km altitude. The estimated fine ash total mass doubles if we consider spherical aggregates instead of irregular aggregates, due to a tighter packing of coating particles. The highest estimated fine ash mass for the upper and lower clouds is of 3.81⋅108±1.41⋅108 kg (12:40 UTC) and of 11.61⋅108±4.30⋅108 kg (13:50 UTC), respectively. Estimating the exact amount of erupted fine ash mass, mainly during hydromagmatic eruptions, is challenging and further works should investigate aggregates where the ice fraction is higher than the ash fraction.
Earth System Science stands as the future operating framework to monitor the pulse of the Earth, and to diagnose and address the challenges of global change. Magmatism and volcanism are primary processes connecting the solid Earth to the atmosphere, hydrosphere, and biosphere. In addition to regulating the Earth system, they are both an unavoidable source of hazards and a tremendous resource of energy and raw materials. Accessing magma is the necessary next step in the exploration of our planet. It will enable us to develop next-generation geothermal energy (magma energy), to transform volcano monitoring strategies, and perhaps even to alleviate volcanic activity. Recent exploratory geothermal drilling activities around the world have serendipitously encountered shallow magma bodies in the Earth. Following these remarkable magma drilling occurrences, the Krafla Magma Testbed (KMT) has been established in Iceland in order to create the first magma observatory – a world-class international in situ magma laboratory with access to the magma-rock-hydrothermal boundary through wells suitable for advanced studies and experiments. Here we review the importance of magma in the Earth system, present the multifaceted need for magma observatories and introduce the benefits of KMT as we enter a new generation of energy demands and resilience strategies.
Constraining sea level at the Last Glacial Maximum (LGM) is spatially restricted to a few locations. Here, we reconstruct relative sea-level (RSL) changes along the Atlantic coast of Africa for the last ~30 ka BP using 347 quality-controlled sea-level datapoints. Data from the continental shelves of Guinea Conakry and Cameroon indicate a progressive lowering of RSL during the LGM from −99.4 ± 5.2 m to −104.0 ± 3.2 m between ~26.7 ka and ~19.1 ka BP. From ~15 ka to ~7.5 ka BP, RSL shows phases of major accelerations up to ~25 mm a⁻¹ and a significant RSL deceleration by ~8 ka BP. In the mid to late Holocene, data indicate the emergence of a sea-level highstand, which varied in magnitude (0.8 ± 0.8 m to 4.0 ± 2.4 m above present mean sea level) and timing (5.0 ± 1.0 to 1.7 ± 1.0 ka BP). We further identified misfits between glacial isostatic adjustment models and the highstand, suggesting the interplay of different ice-sheet meltwater contributions and hydro-isostatic processes along the wide region of Atlantic Africa are not fully resolved.
Phreatic events may represent precursors of magmatic eruptions or occur independently as single or multiple episodes at volcanoes with hydrothermal systems. We examine the Breccia De Fiore deposit from the prolonged phreatic activity during September–October 1873 at the La Fossa cone of Vulcano (Aeolian Islands, Italy). By integrating data from historical chronicles, stratigraphy, sedimentology, physical analyses, and 3D numerical simulations, we investigate eruption dynamics. The sedimentological characteristics of the deposits, asymmetrically dispersed along the north-western flank of the cone, are interpreted as the simultaneous emplacement of pyroclastic density currents and ballistic projectiles. Numerical simulations model the eruptive mixture as an Eulerian gas-particle fluid coupled with Lagrangian ballistic particles. Results suggest the deposit originated from multiple, shallow, low-magnitude explosions (< 5 × 10 ⁴ m ³ cumulative volume). The deposit dispersal is well reproduced by simulating explosions from an inclined vent, driven by pressure build-up (up to 5 MPa) at shallow depths (< 150 m) within the hydrothermal system. This study helps constrain critical parameters of phreatic scenarios at La Fossa volcano, including erupted mass and specific energy, emphasising the hazards posed by such small events and the crucial need for improving hazard assessment, especially given the close presence of populated, touristic sites.
The volcanic region of Mt. Etna (Italy) has a well-documented historical seismic activity, with records of seismic and volcanic events on the volcano dating back to late 1633. This historical data, covering a time span longer than that recorded by instrumental seismological data, is a testament to the reliability of the intensity-magnitude relations, the only means to obtain macroseismic information, the sole indicator of the energy released by earthquakes. Previous studies in the literature have proposed various methods for converting epicentral intensity into macroseismic magnitude for the Etna region. Still, these methods were based on older datasets with limited instrumental data. The updated relationship proposed in the paper significantly improves the accuracy of macroseismic magnitude estimates, aligning them more closely with local magnitudes calculated for recent earthquakes. The study uses a dataset of 58 volcano-tectonic events from 1997 to 2018, with magnitudes between 2.5 and 4.8 and intensities ranging from IV to VIII on the EMS scale. The instrumental magnitudes were obtained from the Mt. Etna seismic catalogue and the Italian seismological database, while macroseismic data were sourced from the macroseismic catalogue of Etnean earthquakes. In the volcanic area of Etna, macroseismic epicenters are often located very close to the sites where the maximum intensity is observed, this is due to the strong attenuation of seismic energy and the shallowness of the epicenters. For this reason, the epicentral intensity is generally assumed to be equal to the maximum intensity. The new relationship is tailored explicitly for shallow earthquakes (H ≤ 3 km), which are the most recurrent. It includes a correction factor for depth, making it applicable to deeper events and enhancing its relevance in real-world scenarios.
Sulfur dioxide (SO2) is sourced by degassing magma in the shallow crust; hence its monitoring provides information on the rates of magma ascent in the feeding conduit and the style and intensity of eruption, ultimately contributing to volcano monitoring and hazard assessment. Here, we present a new algorithm to extract SO2 data from the TROPOMI imaging spectrometer aboard the Sentinel-5 Precursor satellite, which delivers atmospheric column measurements of sulfur dioxide and other gases with an unprecedented spatial resolution and daily revisit time. Specifically, we automatically extract the volcanic clouds by introducing a two-step approach. Firstly, we used the Simple Non-Iterative Clustering segmentation method, which is an object-based image analysis approach; secondly, the K-means unsupervised machine learning technique is applied to the segmented images, allowing a further and better clustering to distinguish the SO2. We implemented this algorithm in the open-source Google Earth Engine computing platform, which provides TROPOMI imagery collection adjusted in terms of quality parameters. As case studies, we chose three volcanoes: Mount Etna (Italy), Taal (Philippines) and Sangay (Ecuador); we calculated sulfur dioxide mass values from 2018 to date, focusing on a few paroxysmal events. Our results are compared with data available in the literature and with Level 2 TROPOMI imagery, where a mask is provided to identify SO2, finding an optimal agreement. This work paves the way to the release of SO2 flux time series with reduced delay and improved calculation time, hence contributing to a rapid response to volcanic unrest/eruption at volcanoes worldwide.
The sensitivity of Global Navigation Satellite System (GNSS) receivers to ionospheric disturbances and their constant growth are nowadays resulting in an increased concern of GNSS users about the impacts of ionospheric disturbances at mid-latitudes. The geomagnetic storm of June 2015 is an example of a rare phenomenon of a spill-over of equatorial plasma bubbles well north from their habitual. We study the occurrence of small- and medium-scale irregularities in the North Atlantic Eastern Mediterranean mid- and low-latitudinal zone by analysing the amplitude of the scintillation index S4 and rate of total electron content index (ROTI) measurements during this storm. In addition, large-scale perturbations of the ionospheric electron density were studied using ground and space-borne instruments, thus characterising a complex perturbation behaviour over the region mentioned above. The involvement of large-scale structures is emphasised by the usage of innovative approaches such as the ground-based gradient ionosphere index (GIX) and electron density and total electron content gradients derived from Swarm satellite data. The multi-source data allow us to characterise the impact of irregularities of different scales to better understand the ionospheric dynamics and stress the importance of proper monitoring of the ionosphere in the studied region.
We present the first application of Full‐Waveform Inversion (FWI) for a radially anisotropic 3D velocity model of the lithosphere beneath central Italy. The retrieved model CI23 constrains P‐wave (VPV , VPH ) and S‐wave velocities (VSV , VSH ) in the period range 8–50 s. CI23 model correlates well with regional lithological formations and highlights a negative radial anisotropy anomaly VSH<VSV localized beneath the epicentral region of the 2016–2017 Amatrice‐Visso‐Norcia (AVN) seismic sequence. An opposite trend (positive radial anisotropy anomaly, i.e. VSH>VSV ) is observed in the area affected by the 2009 L’Aquila (AQ) seismic sequence. We interpret the velocity anomalies in terms of local tectonic structures, particularly the Olevano‐Antrodoco‐Sibillini (OAS) thrust—Gran Sasso Thrust (GST) systems, while also considering possible evidence of overpressured fluids and fluid migration. Additionally, the observed anomalies may reflect transient velocity variations induced by the ANV and AQ seismic sequences.
The increase of ground deformation, seismicity, and gas emission is underlining a remarkable unrest at Campi Flegrei caldera. The direct involvement of magma has been invoked to explain the deformation and space/time changes of velocity anomalies at shallow crustal depths. Here, we show that detailed imaging of seismicity, improved by phase detection with machine-learning algorithms, and velocity models shed light on the active processes at the unresting caldera. Shallow seismicity tracks the fluids uprise, while deeper seismicity, aligning on an almost continuous ring on the top of the inferred magmatic source, indicates deep-seated-related, induced stresses. Our results offer valuable constraints to the challenging aspects of tracking upward migration of magma and magmatic fluids from depth, crucial in terms of hazard assessment and forecasting at Campi Flegrei.
The Apennines are a tectonically active belt that has experienced significant earthquakes (Mw> 6). The largest events primarily occurred along the chain axis, where a complex system of normal faults accommodates 2–3 mm/yr of SW‐NE oriented extension, as precisely measured by a dense Global Navigation Satellite System network. Geodetic strain rates are now frequently used in earthquake hazard models; however, the impact of using such estimates, computed through different methods, for seismic hazard assessments may be difficult to evaluate. This study explores the relationship between geodetic strain rates and seismicity rates in the Apennines using three distinct horizontal strain rate maps and an instrumental seismicity catalog. We find that the principal directions of geodetic strain rate are kinematically consistent with those of strain release. We estimate a spatially heterogeneous seismogenic thickness using the distribution of earthquake depths, and we isolate likely independent seismicity using three different declustering methods. We observe a correlation between independent seismicity rates and the magnitude of strain rate, which can be represented by either a linear or, more accurately, by a power‐law relationship. The variability in the strain‐seismicity relationship depends on the combination of independent seismic catalogs and strain rate maps. This relationship is primarily influenced by the declustering technique more than the choice of the strain rate map and, in particular, by the number of aftershocks excluded during declustering. Seismicity models derived from these combinations were used to estimate and compare the seismic moment release rate with the tectonic moment rate estimated from strain rate maps and seismogenic thickness. Findings indicate that the tectonic moment rate exceeds the seismic moment release rate. We highlight uncertainties and potential causes, one of which could be a possible aseismic release of part of the moment rate.
The mechanical and hydraulic behavior of faults in geothermal systems is strongly impacted by fluid‐induced alteration. However, the effect of this alteration on fault properties in geothermal reservoirs is under documented. This affects our ability to model the properties of subsurface structures, both in reservoirs and caprocks, and potential hazards during geothermal exploitation. We investigated fault rocks from the caprock of a fossil hydrothermal system in the Apennines of Italy. We combined field structural observations with mineralogical and microstructural analyses of faults that guided the circulation of hydrothermal fluids and steered the caprock formation. We also performed friction experiments and permeability tests on representative fault rocks. We document fault weakening induced by the effect of hydrolytic alteration leading to the enrichment of clay minerals along the slip surfaces of major faults. Alunite‐clay‐rich rocks are much weaker (friction coefficient 0.26 < μ < 0.45) than the unaltered protolith (trachyte, μ = 0.55), favoring strain localization. The late‐stage enrichment of clays along faults induces a local decrease in permeability of three orders of magnitude (1.62 × 10⁻¹⁹ m²) with respect to the surrounding rocks (1.96 × 10⁻¹⁶ m²) transforming faults from fluid conduits into barriers. The efficiency of this process is demonstrated by the cyclic development of fluid overpressure in the altered volcanic rocks, highlighted by chaotic breccias and hydrofracture networks. Permeability barriers also enhance the lateral flow of hydrothermal fluids, promoting the lateral growth of the caprock. Velocity‐strengthening frictional behavior of alunite‐clay‐rich rocks suggests that hydrolytic alteration favors stable slip of faults at low temperature.
Sangay volcano (Ecuador) shows a quasi-continuous activity at least since the seventeenth century and has produced several eruptions which affected towns and cities at considerable distance (up to > 170 km). For this reason, despite its remote location, recent efforts were aimed at reviewing its volcanic history, quantifying the occurrence probability of four eruptive scenarios of different magnitude (Strong Ash Venting, Violent Strombolian, sub-Plinian, and Plinian) and the associated uncertainty, and, for each eruptive scenario, estimating the probability distribution of key eruptive source parameters (fallout volume, average plume height, and eruption duration). In this study, we utilize such information to produce probabilistic hazard maps and curves. To this aim, we use coupled plume and dispersal models (PLUME-MOM-TSM and HYSPLIT, respectively) with the application of a novel workflow for running an ensemble of thousands of simulations following a sto-chastic sampling of input parameters. We produced probabilistic hazard maps for each scenario by considering four ground load thresholds (i.e., 0.1, 1, 10, and 100 kg/m 2) and two types of model initialization strategies, based on the elicited total deposit volume and on the elicited plume height, respectively, which produced non-negligible differences. In addition, we produced hazard curves for nine sites of interest from a risk perspective, corresponding to towns/cities potentially affected by tephra accumulation. Finally, we also derived combined maps by merging maps of single scenarios with their probability of occurrence as obtained from expert elicitation. Results indicate that in case of a future eruption, even for a moderate-scale one (Violent Strombolian), probability of tephra accumulation larger than 1 kg/m 2 is relatively high (from 21 to 24% considering different model initializations) in the town of Guamote, i.e., the most severely affected site among those tested (43 km W of Sangay). For larger-scale events (i.e., sub-Plinian), the impact of tephra accumulation results to be significant even for the city of Guayaquil (176 km W of Sangay), with probability of tephra accumulation larger than 1 kg/m 2 from 3 to 22% considering different model initializations. For maps combining single maps of historically observed scenarios, the probability (%-[5 th-Mean-95 th ]) of having ≥ 10 kg/m 2 for Guamote is [4-13-25] as maximum values.
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