INGV Osservatorio Nazionale Terremoti

Abstract Magmatic intrusions, eruptions and flank collapses are frequent processes of volcano dynamics, inter-connected at different space and time scales. The December 2018 recrudescent episode at Mt. Etna is an exemplary case where a sudden intrusive event culminated with a short eruption, intense seismicity and a shallow large strike-slip earthquake at the edge of the eastern sliding flank. Here, we show that high resolution velocity models and transient changes of V P and V P /V S resolve the magma intrusion through a dyke and local stress increase at the base of the unstable flank, inducing the collapse. Episodic brittle faulting occurs at the edge of the sliding sector, locally contributed by high fluid pressure. The feedback between magma ascent, stress changes and flank collapse is driving the volcano dynamics, with processes ranging from long term to transient episodes.

A full review of the 79 CE Plinian eruption of Vesuvius is presented through a multidisciplinary approach, exploiting the integration of historical, stratigraphic, sedimentological, petrological, geophysical, paleoclimatic, and modelling studies dedicated to this famous and devastating natural event. All studies have critically been reviewed and integrated with original data, spanning from proximal to ultradistal findings of the 79 CE eruption products throughout the Mediterranean. The work not only combines different investigation approaches (stratigraphic, petrological, geophysical, modelling), but also follows temporally the 79 CE eruptive and depositional events, from the magma chamber to the most distal tephras. This has allowed us first to compile a full database of all findings of those deposits, then to relate the products (the deposits) to the genetic thermomechanical processes (the eruption), and lastly to better assess both the local and regional impacts of the 79 CE eruption in the environment. This information leads to a number of open issues (e.g., regional environmental impact vs. local pyroclastic current impact) that are worthy of further investigations, although the 79 CE eruption of Vesuvius is one of the best studied eruptions in volcanology. The structure of the work follows three macro-categories, the historical aspects, the products, and the processes of the 79 CE eruption. For each investigation approach (from stratigraphy to modelling), all dedicated studies and original data are discussed. The open issues are then synthesized in the discussion under a global view of Plinian eruptions, from the magma setting to its dispersion as pyroclasts flowing on the surface vs. falling from the volcanic plume. In this way, a lesson from the past, in particular from the well-studied 79 CE eruption of Vesuvius, will be of help for a better synchronization of processes and products in future developments. Lastly, various aspects for volcanic hazard assessment of Plinian eruptions are highlighted from the tephra distribution and modelling points of view, as these large natural phenomena can have a larger impact than previously thought, also at other active volcanoes.

Abstract The continuous redistribution of water involved in the hydrologic cycle leads to deformation of the solid Earth. On a global scale, this deformation is well explained by the loading imposed by hydrological mass variations and can be quantified to first order with space‐based gravimetric and geodetic measurements. At the regional scale, however, aquifer systems also undergo poroelastic deformation in response to groundwater fluctuations. Disentangling these related but distinct 3D deformation fields from geodetic time series is essential to accurately invert for changes in continental water mass, to understand the mechanical response of aquifers to internal pressure changes as well as to correct time series for these known effects. Here, we demonstrate a methodology to accomplish this task by considering the example of the well‐instrumented Ozark Plateaus Aquifer System (OPAS) in the central United States. We begin by characterizing the most important sources of groundwater level variations in the spatially heterogeneous piezometer dataset using an Independent Component Analysis. Then, to estimate the associated poroelastic displacements, we project geodetic time series corrected for hydrological loading effects onto the dominant groundwater temporal functions. We interpret the extracted displacements in light of analytical solutions and a 2D model relating groundwater level variations to surface displacements. In particular, the relatively low estimates of elastic moduli inferred from the poroelastic displacements and groundwater fluctuations may be indicative of aquifer layers with a high fracture density. Our findings suggest that OPAS undergoes significant poroelastic deformation, including highly heterogeneous horizontal poroelastic displacements.

Abstract In this study, we assess the spectral characteristics of seismic noise at the sites of the Italian Seismic Network and its spatio‐temporal variability. The evaluation of noise is crucial for the assessment of the detection capability of a seismic network. We selected a set of 233 stations, those equipped with broadband velocimeters (with corner period 40 s) and operating continuously for at least four consecutive years. The analysis was carried out in the frequency band from 0.025 to 30 Hz, in accordance with the seismic sensors bandwidth. We estimated the Power Spectral Density (PSD) of the seismic noise for fixed temporal windows and then we calculated the Probability Density Functions (PDF) at each station. Exploiting the large data set available, we have been able to: (a) describe the characteristics of the noise power at each site; (b) investigate both temporal and spatial variations of the background noise, revealing correlations of the noise levels with natural and anthropogenic noise sources; (c) propose an empirical relationship linking the “microseismic” noise (i.e., 0.12–1.2 Hz) with the geographical features of the site hosting the seismic station; (d) establish the baselines of a new seismic noise model that could be considered as a new reference for the Italian territory.

The 2016-2017 Central Italy earthquake sequence struck the central Apennines between August 2016 and October 2016 with Mw ∈ [5.9; 6.5], plus four earthquakes occurring in January 2017 with Mw ∈ [5.0; 5.5]. We study Global Positioning System time series including near- and far-field domains. We use a variational Bayesian independent component analysis technique to separate the post-seismic deformation from signals caused by variation of the water content in aquifers at hundreds of meters of depth and of the soil moisture. For each independent component, realistic uncertainties and a plausible physical explanation are provided. We focus on the study of afterslip on the main structures surrounding the mainshock, highlighting the role played by faults that were not activated during the co-seismic phase in accommodating the post-seismic deformation. We report aseismic deformation occurring on the Paganica fault, which hosted the Mw 6.1 2009 L'Aquila earthquake, suggesting that static stress transfer and aseismic slip influence the recurrence time of nearby (∼50 km further south of the mainshocks) segments. A ∼2-3 km thick subhorizontal shear-zone, clearly illuminated by seismicity, which bounds at depth the west-dipping normal faults where the mainshocks nucleated, also shows aseismic slip. Since afterslip alone underestimates the displacement in the far-field domain, we consider the possibility that the shear zone marks the brittle-ductile transition, assuming the viscoelastic relaxation of the lower crust as a mechanism contributing to the post-seismic displacement. Our results suggest that multiple deformation processes are active in the first 2 years after the mainshocks.

Scientists and engineers from the United States and Italy are developing a thermal infrared (TIR) free-flyer concept that forms an essential element of the NASA Surface Biology & Geology (SBG) designated observable and the greater NASA Earth System Observatory (ESO), which also includes observations of aerosols, clouds, convection, and precipitation; mass change; and surface deformation & change. In response to the recommendations from the 2017 National Academies decadal survey for Earth science, NASA initiated the SBG designated observable with five key research and applications focus areas: ecosystems and natural resources, hydrology, weather, climate, and solid Earth. SBG includes spaceborne measurements of hyperspectral imagery in the visible to shortwave infrared (0.4-2.5 um) and multispectral imagery in the mid and thermal infrared (3–12 um) that provide the remote sensing data needed to inform each research and applications area. High-level TIR data products include Earth surface temperature & emissivity, evapotranspiration, substrate composition, volcanic plumes, and high-temperature features. While the science, applications, and technology build on prior mission studies conducted for more than a decade, it has only been recently that a joint team of scientists and engineers from the NASA Jet Propulsion Laboratory (JPL), Agenzia Spaziale Italiana (ASI), Istituto Nazionale Geofisica e Volcanologia (INGV), and the Istituto Nazionale Astrofisica (INAF) have developed a compelling concept for a TIR free-flyer. In this concept, the TIR instrument is an eight-band radiometer. Seven of the bands are between 3 and 12 um with an additional band at 1.65 um. The instrument's 68.8 deg total viewing angle and the free-flyer's 665 km operational altitude results in a ground sampling distance (GSD) of <60 m at nadir, produces a swath width of 935 km, and allows for a 2-3-day revisit time. A two-band visible and near infrared (VNIR) camera, with <30 m GSD at nadir and 935 km swath width, will complement the TIR instrument. VNIR high-level data products include top & bottom of atmosphere reflectance and normalized difference vegetation indices (NDVI). The TIR instrument and VNIR camera will be mounted on a PLATiNO+ spacecraft, a multi-application, reconfigurable, and scalable platform. The launcher selected for the TIR free-flyer is the VEGA-C. To maximize the science and applications benefits the SBG-TIR free-flyer team are collaborating with personnel from the ESA Land Surface Temperature Monitoring mission (LSTM) as well individuals from the Thermal Infrared Imaging Satellite for High-resolution Natural resource Assessment (TRISHNA), a joint mission by CNES and ISRO. Pre-Phase A concept studies for the SBG-TIR free-flyer commenced in the spring 2021. This allows for the concept to be refined; for technical risks to be identified and mitigated, as necessary; and strategies for reducing the development schedule to be defined and assessed before conducting a NASA-ASI Mission Concept Review (MCR) in the spring of 2022 and a NASA Key Decision Point-A (KDP-A) as early as the summer of 2022. These are key milestones in being able to launch and begin operating the SBG-TIR free-flyer in the second half of the decade, so that many of the questions posed by the National Academies in the 2017 decadal survey can be answered.

Abstract We present the first 3D crustal model of the epicentral region of the 1980, M w 6.9, normal‐faulting Irpinia earthquake (southern Italy) determined by jointly interpreting the CROP‐04 deep seismic profile, a grid of commercial seismic lines, deep exploration wells, and a high‐resolution Local Earthquake Tomography. Despite numerous seismotectonic surveys and source studies of the background seismicity recorded by dense networks, a complete 3D geological model of the mid‐upper crust was still lacking in the region. The architecture of the Neogene fold‐and‐thrust belt is also debated, with competing thin‐ and thick‐skinned tectonic interpretations. We use the 3D geological model derived from subsurface exploration data to interpret the upper crustal tomographic velocities in terms of rock physical properties, while V p and V p / V s anomalies provide inferences on the deep structural setting down to 12 km depth. We find that a thick‐skinned deformation style allows explaining the geometry of Pliocene fold‐and‐thrust systems deforming the Apulian carbonates but also deeper Permo‐Triassic metasediments and the Paleozoic crystalline femic basement. Inherited compressional structures and lithological heterogeneities control background seismicity occurring at two crustal levels. Fluid‐driven shallow seismicity (<4–6 km) concentrates in a high‐ V p / V s wedge of fractured, brine‐saturated Mesozoic stiff rocks delimited by the 1980 earthquake faults. Deep seismicity (9–14 km) clusters instead within the low‐ V p / V s crystalline basement underneath the Apulian carbonate ramp‐anticlines. Commercial seismic data allow us to identify the Irpinia Fault, the main fault ruptured by the 1980 earthquake, reinforcing its previous interpretations as an immature structure with subtle geological and geophysical evidence.

Nonlinear dynamical systems are ubiquitous in nature and they are hard to forecast. Not only they may be sensitive to small perturbations in their initial conditions, but they are often composed of processes acting at multiple scales. Classical approaches based on the Lyapunov spectrum rely on the knowledge of the dynamic forward operator, or of a data-derived approximation of it. This operator is typically unknown, or the data are too noisy to derive its faithful representation. Here, we propose a data-driven approach to analyze the local predictability of dynamical systems. This method, based on the concept of recurrence, is closely linked to the well-established framework of local dynamical indices. When applied to both idealized systems and real-world datasets arising from large-scale atmospheric fields, our approach proves its effectiveness in estimating local predictability. Additionally, we discuss its relationship with other local dynamical indices, and how it reveals the scale-dependent nature of predictability. Furthermore, we explore its link to information theory, its extension that includes a weighting strategy, and its real-time application. We believe these aspects collectively demonstrate its potential as a powerful diagnostic tool for complex systems.

Abstract During the extended activity of Mount Etna volcano in February–April 2021, three distinct paroxysmal events took place from February 21 to 26, which were associated with a very uncommon transport of the injected upper‐tropospheric plumes toward the north. Using a synergy of observations and modeling, we characterized the emissions and three‐dimensional dispersion for these three plumes, monitored their downwind distribution and optical properties, and estimated their radiative impacts at selected locations. With a satellite‐based source inversion, we estimate the emitted sulfur dioxide (SO 2 ) mass at an integrated value of 55 kt and plumes injections at up to 12 km altitudes, which qualifies this series as an extreme event for Mount Etna. Then, we combine Lagrangian dispersion modeling, initialized with measured temporally resolved SO 2 emission fluxes and altitudes, with satellite observations to track the dispersion of the three individual plumes. The transport toward the north allowed the height‐resolved downwind monitoring of the plumes at selected observatories in France, Italy, and Israel, using LiDARs and photometric aerosol observations. Volcanic‐specific aerosol optical depths (AODs) in the visible spectral range ranging from about 0.004 to 0.03 and local daily average shortwave radiative forcing (RF) ranging from about −0.2 to −1.2 W m −2 (at the top of atmosphere) and from about −0.2 to −3.0 W m −2 (at the surface) are found. The composition (possible presence of ash), AOD, and RF of the plume have a large inter‐plume and intra‐plume variability and thus depend strongly on the position of the sampled section of the plumes.

SUMMARY The western Balkans occupy a region influenced by two major active tectonic processes: the collision between the Adriatic Region and the Dinarides in the west, and the extension of the Aegean Region and its surroundings as they move towards the Hellenic Trench. An understanding of the kinematics and dynamics of the western Balkans has significance for our understanding of continental tectonics in general, and is the object of this paper. The region is rich in observational data, with many well-studied earthquakes, good geodetic coverage by GNSS (Global Navigation Satellite System) and abundant exposure of active faulting and its associated geomorphology, especially within the Mesozoic carbonates that cover large sectors of the extensional areas. We first use such observations to establish the regional kinematic patterns, by which we mean a clarification of how active faulting achieves the motions observed in the deforming velocity field obtained from GNSS measurements. We then use geomorphological observations on the evolution of drainage systems to establish how kinematic and faulting patterns have changed and migrated during the Late Neogene-Quaternary. The kinematics, and its evolution, can then be used to infer characteristics of the dynamics, by which we mean the origin and effect of the forces that control the overall deformation. The principal influences are: (i) the distribution and evolution of gravitational potential energy (GPE) contrasts arising from crustal thickness variations and elevation, in particular the growth of topography by shortening in the Albanides–Hellenides mountain ranges and the high elevation of mainland Greece relative to the Mediterranean seafloor and (ii) the ability of the boundaries of the region, along the Adriatic coast and in the Hellenic Trench, to support the forces arising from those GPE contrasts. The evolution in space and time indicates an interaction between the anisotropic strength fabric of the upper crust associated with faulting, and the more distributed and smoother patterns of flow that are likely to characterize the ductile deformation of the lower, aseismic part of the lithosphere—both of which influence the deformation on the scale of 100–200 km. The persistent argument about whether continental deformation is best described by a continuum or by rigid-block motions is largely a matter of scale and particular location: both are influential in establishing the patterns we see.

Abstract The incompleteness of earthquake catalogs is a well‐known issue caused by our technical limitation in detecting the small‐to very small‐magnitude seismicity falling near or below the background seismic noise. The detection of small‐magnitude events is fundamental for improving our knowledge of geometry and kinematics of seismogenic sources and the spatio‐temporal characteristics of seismicity, thus leading to better models for seismic hazard. Template‐matching (TM) is a powerful technique that, based on similarity measure (cross‐correlation) of seismic waveforms, allows to detect hidden earthquakes that are similar to known events (called templates). The high computational effort often limits such technique to small areas and for short time frames (less than 1 year). In this work, we present the first application of template‐matching at regional scale for the Italian Peninsula, focusing on the Southern Apennines. We use about 3,600 high‐quality events as templates, scanning 6‐year long continuous recordings (2009–2014), at more than 180 stations of the INGV network. About 20,000 new events are found, showing a comparable quality to the template catalog in terms of hypocentral solution, reaching a decrease of the magnitude of completeness of about one unit. To highlight the improved quality of the TM catalog, we report two main examples regarding the Sannio‐Matese area, where TM allowed us to unravel relevant details on the spatio‐temporal distribution of the local seismicity.

Abstract The 2013 Ruisui earthquake represents the first unequivocal evidence of the activity of the Central Range fault (CRF) in central Longitudinal Valley, Taiwan. Using a joint Bayesian finite‐fault source inversion of Global Navigation Satellite System and strain time series, we infer that coseismic rupture occurred between 4 and 19 km depth with maximum slip of 0.5 m located near the hypocenter. We then apply a variational Bayesian independent component analysis approach to displacement signals to infer a 3‐months long afterslip located in the near‐source region. This observation represents the first evidence of aseismic slip on the CRF. Combining geodetic and seismological analysis with simulations based on rate‐and‐state friction mechanics, we analyze the interplay between seismic and aseismic deformation during the earthquake sequence. We observe that afterslip is the dominant postseismic deformation mechanism, with >95% of the moment being released aseismically in the postseismic phase and also likely represents the driving force controlling aftershock productivity. Finally, we infer the presence of a shallow velocity strengthening zone (∼0–4 km depth) associated with spatially heterogeneous slip during the postseismic phase with maximum slip of 0.18 m located above the zone of maximum coseismic deformation.

Abstract The Rhenish Massif in Central Europe, which includes the Eifel Volcanic Fields, has shown ongoing ground deformation and signs of possible unrest. A buoyant plume exerting uplift forces at the bottom of the lithosphere was proposed to explain such deformation; the hypothesis of (possibly concurrent) melt accumulation in the crust/lithospheric mantle has not been explored yet. Here, we test deformation models in an elastic half‐space considering sources of varying aspect ratio, size and depth. We explore the effects of data coverage, noise and uncertainty on the inferred source parameters. We find that the observed deformation would require melt accumulation in sub‐horizontal sill‐like structures expanding at the rate of up to ∼0.045 km 3 /yr. We discuss feasibility, limitations and possible interpretations of our resulting models and elaborate on further observations which may help constrain the structure of the Rhenish Massif magmatic system.

The purpose of this work is to provide the methodological and instrumental framework for the establishment of a new absolute gravity and height reference network in Sicily. The aim of the network is to contribute to the new reference systems in the Italian area, useful for the scientific and technological activities related to the gravity field and to the proper definition of a modern height system in this region. The network is composed of 5 stations, evenly distributed to form a large mesh, which roughly covers the entire Sicily. Since four of the five selected stations were measured also in the 1990s, it was also possible to evaluate whether long-term gravity changes occurred at these sites (basic requirement for a reference network) and check the long-term ground deformation patterns, using data from the closest GPS/GNSS stations. The observed gravity changes over a time interval of about 30 years at the absolute stations and in the surrounding areas, confirm the long-term stability of the selected areas/sites.

This work presents a new low cost and low power consumption wide-band (5s) three-component seismic sensor, named ETL3D/5s. The sensor is suitable for seismic regional monitoring (local and regional earthquakes), HVSR measurements, seismic microzonation studies and Structural Health Monitoring (SHM) of civil structures. ETL3D/5s includes a set of three 4.5 Hz geophones and an electronic circuit that increases the geophone’s natural period. The sensor exhibits a period of 5 s and a power consumption as low as 75 mW. Changes in ambient temperature have a small effect on the frequency response because a temperature compensation system is also implemented. A small and sturdy cylindrical housing contains the electronic boards and geophones. The housing design was supported by a modal FEM analysis, in order not to affect the frequency response. The chosen materials and parts guarantee protection against atmospheric agents and watertightness (IP68 degree). The sensor noise model, partially confirmed by a field test, predicts a power spectral density of 10 (nm/s)/√Hz at 1Hz.

The purpose of this work is to explore the methodological and instrumental review for the realization of a new absolute gravity and height reference network in Sicily. The aim of the network is to contribute to the new reference systems in the Italian area, useful for all the scientific and technological activities related to the gravity field and to the proper definition of a modern height system in this region. The network is composed of 5 stations, evenly distributed forming a large mesh network which roughly covers the entire Sicily. Since four of the five selected stations were measured also in the 1990s, it was also possible to evaluate the long-term behavior (basic requirement for a reference network) of the gravity values at these stations, as well as the ground deformation patterns in the closest GPS/GNSS stations. The observed gravity changes over a time interval of about 30 years at the absolute stations and in the surrounding areas, confirm the stability of the selected areas/sites over the long time.

<p>FURTHER – “The role of FlUids in the pReparaTory pHase of EaRthquakes in Southern Apennines” is an INGV Departement Strategic Project devoted to define the role of fluids in earthquake genesis. One of the target areas of the multidisciplinary study is Mefite d’Ansanto, which is the largest area of non-volcanic low temperature CO<sub>2</sub> emission field on the Earth. In particular, Work Package 1.4 is dedicated to the application of analysis methodologies in time and frequency domains, aimed to intercept eventual variations in fluid behavior before or in correspondence of local and regional earthquakes, using recordings from the INGV National Seismic Network (IV) and local networks. For this purpose, temporary acquisition surveys have been locally deployed.</p><p>On November 20, 2020, a stand-alone seismic station equipped with a Guralp CMG40T 60s broadband sensor, was installed close to the Mefite emission field. In this study we analyze some characteristics of the local seismicity, e.g., frequency content, energy temporal pattern (RMS) and polarization (Montalbetti et al., 1970), and estimate site effects (Nakamura, 1989; http://www.geopsy.org/). Here we present the first results of the ongoing investigation of the seismic noise wavefield in the Mefite area. The temporal pattern of the retrieved seismological observables is compared with the meteorological parameters, such as temperature and rainfall, to find possible relationships with exogenous factors.</p><p>Preliminary analysis of the waveforms acquired by the stations of the (IV) have been also performed. We selected the stations inside a radius of 30 km from Mefite area to eventually retrieve  the fluid dynamics footprint in the recorded wavefield.</p><p>The identification of the wavefield and site characteristics will be useful to define the features of the next survey planned in the area.</p><p> </p><p>References</p><p>Montalbetti, J. R., Kanasevich, E. R. (1970): Enhancement of teleseismic body phase with a polarization filter. Geophys. J. Int. 21 (2), 119–129.</p><p>Nakamura, Y. (1989). A method for dynamic characteristics estimation of subsurface using microtremor on the ground surface, Railway Technical Research Institute, Quarterly Reports, 30 (1), 25-33.</p>

Earthquakes are complex natural phenomena that involve multiple spatio-temporal scales. To understand the physical/chemical processes responsible for the faulting that earthquakes occur on, a multidisciplinary approach is highly recommended. Near Fault Observatories (NFOs) aim at providing high-precision and spatio-temporally dense multidisciplinary near fault data, enabling the generation of innovative scientific products.The Alto Tiberina Near Fault Observatory (TABOO-NFO) is a permanent monitoring infrastructure around the Alto Tiberina Fault (ATF). The ATF is a 60 km long very low-angle normal fault (mean dip 20°) located along a 3 mm/yr extending sector of the Northern Apennines (Central Italy). The presence of repeating earthquakes on the ATF, as well as a steep gradient in crustal velocities measured by GNSS stations, suggest that portions of the ATF are creeping aseismically. Both laboratory and theoretical studies indicate that any given patch of a fault can creep, nucleate slow earthquakes, and host large earthquakes, as also documented in nature for some earthquakes (e.g., Iquique, Tohoku and Parkfield earthquakes). Nonetheless, how a fault patch switches from one mode of slip to another as well as the interaction between creep, slow and regular earthquakes are still poorly documented by near field observation.TABOO is a state-of-the-art dense network, managed by the Istituto Nazionale di Geofisica e Vulcanologia (INGV), with mean inter-distance of about 5 km between multidisciplinary sensors, deployed both at surface and within shallow boreholes (<250m). Stations record and transmit in real time via dedicated Wi-Fi technology; then data is stored in standard formats on open access thematic portals and distributed via web services (http://fridge.ingv.it). With STAR, during the Fall of 2021 and Spring of 2022, INGV in collaboration with UNAVCO, drilled six 80-160 m deep boreholes surrounding the creeping portion of the ATF, to deploy Gladwin Tensor strainmeters and short period seismometers. Each “observatory” is also equipped with surface GNSS, meteorological instruments, and additional seismic sensors. The two deepest boreholes host fibre optic cables for temperature and strain. The strainmeter array (STAR) instruments are four-gauge strainmeters, from which we can resolve the horizontal strain matrix and measure deformation on the order of nanostrain, and bridge timescales encompassed neither by GNSS nor by Seismometers. With this new suite of instruments TABOO will enable the collection and calibration of strain records with exquisitely high precision, allowing for a quantitative characterization of ATF creep (~1 mm over <1 km2), enhanced monitoring of microseismicity (below Mc 0.5), and allowing correlation between degassing (CO2, Rn) measurements and subsurface strain.Such unique near fault data Illuminating the spatiotemporal characteristics of creep on the ATF including possible stress triggering of larger earthquakes by transient creep events, are needed to address key questions of global importance in the seismic hazards and risk assessment community about the physics that allows for both seismic and aseismic slip on a single fault patch.After presenting the field campaigns, we give an overview of the new data, showing how they enable us to detect new dynamic and static strain features missed by the other in situ instruments.

The Virunga was established in November 2017 as a permanent Supersite with the aim of improving the geophysical scientific research and Geohazards assessment in support of Disaster Risk Reduction (DDR) in the Virunga Volcanic Province and the Lake Kivu basin. The CEOS guarantees a free access to Earth Observatory (EO) data, while the pool of collaboration built around the Supersite potentially supports the access to equipment for ground-based data collection and processing. From November 2017 to November 2019, in addition to implementing the Supersite; collaboration was built between the GVO and the world leading observatories and agencies, the free access to EO data with first steps towards collecting some ground-based data, training of some local scientists, and the adhesion to the Virunga Supersite of world top-level geoscientists in the field of active volcano monitoring and hazards assessment. The later allowed the assessment of volcanic hazards around Nyiragongo and Nyamulagira, which included the production of hazards maps for future volcanic eruptions management, the collection of ground-based data to produce Risk and Recovery mapping.<br> On the evening of May 22^nd 2021, Nyiragongo volcano suddenly erupted from three vents that opened along a system of fractures on the southern flanks of the volcano. Two major lava flows were produced with one having its direction toward Goma city. Fortunately, these lava flows stopped their run before reaching the densely populated areas, with one being only at ~1 km from the Goma international Airport. Still, the lava flows had already destroyed about 3,600 houses while another 1,000 were severely damaged causing at least 30,000 persons to be in the need of shelter and other humanitarian assistance. The volcanic eruption further caused the death of 38 persons, disrupted the water supply infrastructures in Goma and the surrounding: estimated 550,000 persons lost access to water. An intense seismic activity followed the eruption and persisted for ~2 weeks, and caused sever damages to houses and infrastructures such as roads, water and electricity networks. Furthermore, the earthquakes caused important ground deformation in Goma and Gisenyi cities, which brought the fear of magma rising and accumulating beneath Goma and Lake Kivu. This raised a scenario of a new eruption with active vents inside Goma city or Lake Kivu, and led local authorities to evacuate estimated 400,000 people. Virunga Supersite scientific team supported the response to the Nyiragongo 2021 volcanic crisis through data processing, which yielded the production of key information that was delivered to local authorities and supported the management of the volcanic and humanitarian crises.<br> In September 2021 a new effusive activity began inside Nyiragongo main crater, along with a sustained seismic activity and ground deformation to the southern flank of the volcano. The fast renew of the activity denotes the strong and urgent need to starting prepare for the next Nyiragongo volcanic eruption; and the Virunga Supersite is willing to be part of this goal. This preparation strongly need an enhanced monitoring infrastructure that would permit follow up the complex Nyiragongo-Nyamulagira rift-zone volcanism, forecast the spatiotemporal extent of the next eruption which will reduce its impacts. Furthermore, a proper training of local scientists is part of the well properness to the next Nyiragongo crisis, which the Supersite has already started.

The Fucino basin (central Italy) is the largest Plio-Quaternary tectonic depression of the Apennines extensional belt. The basin is bounded to the north and east by two main normal fault systems striking WSW-ENE and NW-SE, respectively. These fault systems controlled the syntectonic depositions of lacustrine and coarse clastic sequences that reach a total thickness of 1.5 km. The NW-SE fault system is the source of the Mw 7.0, 1915 central Italy earthquake and of previous M6-7 earthquakes recognized through paleoseismic trenching. On the other hand, current activity and seismogenic potential of the WSW-ENE structures are uncertain. The shallow architecture of both fault systems (&lt; 2 km depth) is well defined by surface data and seismic reflection profiles, but the fault&amp;#8217;s deep geometry is poorly known. Large uncertainties also regard the crustal structure underneath the basin at seismogenic depths (i.e.; 5-15 km depth) despite a close deep seismic reflection profile (i.e., CROP11 line). The instrumental seismicity occurring beneath the Fucino basin is scarce. On the contrary, an intense activity concentrated to the north (2009, Mw 6.3, L&amp;#8217;Aquila sequence) and 25-30 km to the south, where both low-to-moderate sequences and diffuse swarm-like seismicity were recorded in recent years.&amp;#160;In 2008-2009, a dense passive seismic survey was carried out in the Fucino area to investigate the basin seismic response and local site effects. The temporary network included 18 stations, with an average spacing of 2-3 km, operating in continuous mode with a sampling rate of 125 Hz and equipped with 5 second seismometers.&amp;#160;In this study, we re-processed the data recorded by the Fucino temporary network, integrated by the permanent stations of the Italian seismic network and Abruzzo regional network installed on the surrounding ridges, to construct a new earthquake catalog and perform a local-scale passive tomographic survey.&amp;#160;We used a standard (STA/LTA) algorithm to detect very local weak events in addition to those used in the previous site-effects study. P- and S-wave arrival times of the detected seismic events were hand picked and weighted according to a standard scheme. Seismograms for stations deployed in the Fucino basin show strong complexities especially for P-waves onsets that are often masked by background noise.&amp;#160;We used the final dataset in terms of P- and S-waves arrival times as input for a Local Earthquake Tomography targeting the upper crustal velocity structure and active faults underneath the Fucino basin and surrounding ridges. The tomographic model, presented in terms of Vp and Vp/Vs, aimed at recovering the crustal heterogeneities with a spatial resolution finer with respect to previous tomographic surveys of central Apennines. The 3D distribution of Vp and Vp/Vs and of relocated events helped us to identify the velocity contrasts related to the main faults and to improve our knowledge on their geometry at depth.