Danesi, Stefania

Changes in seismicity with time and location are diagnostic signals for understanding the dynamics of volcanic unrest. We used these signals at the Campi Flegrei caldera, in southern Italy, to investigate how structural changes have determined three styles of unrest since 1982, distinguished by a ground uplift (measured at Pozzuoli, near the centre of the caldera) of 178 cm in 1982–84; a subsidence of 93 cm in 1985–2005; and an uplift of 118 cm between 2005 and November 2023. Double-difference seismic locations and concentrations of seismic energy release have revealed impermeable horizons that correspond to the cap rock and self-sealed base of the geothermal system at depths of 1.5 and 3 km, respectively. Most earthquakes have been shallower than 3 km, consistent with the brittle upper crust being stretched over a zone of pressurization below the geothermal system. The 1982–84 uplift decayed after a major seismic swarm on April 1st, 1984, breached the lower impermeable horizon, which increased the flux of escaping gas and reduced the source pressure. Continued gas escape promoted subsidence until the lower horizon had resealed itself and initiated a new episode of uplift while gas from depth re-accumulated beneath. Compared with 1982–84, a greater proportion of recent seismicity has occurred at shallower depths below the actively degassing fumaroles of Solfatara-Pisciarelli, north-east of Pozzuoli. The associated high seismic b-values, between 1 and 2, are consistent with high fluid pressures and, hence, with locations more favourable to fracturing. Continued uplift may thus persist until fracturing of the shallow crust allows faster rates of gas release and depressurization of the pressure source.

Volcanoes reawakening after long repose must rupture the crust before magma can erupt. Rupture is preceded by repeatable variations in the rate of seismicity with ground movement, which trace the amount of applied stress that is released by local earthquakes. A rupturing sequence has been developing across four episodes of ground uplift at Italy’s Campi Flegrei caldera: in 1950-1952, 1969-1972, 1982-1984 and since 2004. We predicted in 2016 that the approach to rupture would continue after an additional uplift of 30-40 cm at the location of largest movement. We have updated our analysis with new data on changes in the numbers of local earthquakes with amounts of ground movement. Here we show that subsequent events have confirmed our prediction and that the unrest has been changing the structure of Campi Flegrei’s crust. The results provide new constraints for evaluating the volcano’s potential to erupt or to subside without eruption.

The Val d’Agri (VA) oilfield in the Lucanian Apennines (southern Italy), represents the largest onshore in Europe. Since the 1990's, hydrocarbons are produced from a fractured carbonate reservoir with an average extraction rate of 7*104 barrels/day of oil and 3*106 Smc/day of gas. Part of the wastewater has been re-injected since 2006 into a marginal portion of the reservoir by a high-rate well (Costa Molina 2, CM2). Charged by the Italian oil and gas safety authority, the National Institute of Geophysics and Volcanology (INGV) monitors the VA industrial hydrocarbon operations through the research activity of a dedicated working group (CMS, Centro di Monitoraggio del Sottosuolo) and according to the governmental monitoring guidelines. The CMS operates the real-time acquisition and offline analyses of seismic data recorded at 56 seismic stations associated with public and private local seismic networks. The principal aim of the CMS is to investigate the risk associated with industrial activities that can induce or trigger seismic events by producing stress changes within the upper crustal volume. Previous works have highlighted a spatio-temporal relationship between micro-seismicity (ML ≤ 2.2) and wastewater injection, delineating a NE-dipping back-thrust near the CM2. Part of the microseismicity recorded in the southwestern portion of the VA has also been associated with the water level changes of the Pertusillo lake. One of the main challenges is to define an accurate structural setting of the VA to understand the potential of earthquakes in the area and investigate the presence of active faults. The VA consists of a Quaternary extensional tectonic basin and it is one of the areas of highest seismic hazard in Italy (Basilicata, 1857, M7 earthquake). The basin is bounded by two parallel and oppositely dipping normal fault systems: the Monti della Maddalena Fault System (MMFS) on its western side and the Eastern Agri Fault System (EAFS) on the eastern one. The characterization of the ongoing tectonic activity of the MMFS and EAFS, and their hierarchical relationship is still generating debate among the scientific community. We adopt a multidisciplinary approach based on detailed geological-structural, geophysical and seismic analyses, and electrical resistivity tomography, aimed at reconstructing the subsurface geology of the area and recognizing and characterizing the active and capable faults, and the associated potential for local seismic hazard. We present and discuss the results of this work, focusing on the relative location of seismic events that occurred between March and June 2022. The outcomes allow inferring interesting geologic constraints, highlighting the relationships between the distribution of local seismicity and the structural setting of the area in the uppermost crust (depth < 6 km).

We analyze seismic time series collected during experimental campaigns in the area of the David Glacier, South Victoria Land, Antarctica, between 2003 and 2016. We observe hundreds of repeating seismic events, characterized by highly correlated waveforms (cross-correlation > 0.95), which mainly occur in the floating area between the grounding and the floating line of the ice stream. The joint analysis of seismic occurrences and observed local tide measurements seem to show that seismicity is not triggered by a seasonal, regular, periodic forcing such as the ocean tide, but more likely by transient irregular impulses. We consider possible environmental processes and their impact on the coupling between the glacier flow and the bedrock brittle failure. Our results suggest that clustered and repeated seismic events may be correlated with transient episodes of mass ice discharge (observed by satellite GRACE and GRACE-FO experiments) through the subglacial hydrographic system that originates upstream of the glacier and extends to the grounding zone, lubricating the interface with the bedrock.

Nel sottosuolo della Val D’Agri (Basilicata) è collocato il più grande giacimento di idrocarburi continentale (a terra) Europeo, che viene sfruttato a partire degli anni 90 da un concessionario multinazionale. Su proposta del MISE la Val D’Agri è stata inserita tra i siti pilota per la sperimentazione degli Indirizzi e Linee Guida per il monitoraggio della sismicità, delle deformazioni del suolo e delle pressioni di poro per le aree interessate delle attività antropiche. Per monitorare un’eventuale influenza delle attività produttive sull’attività sismica locale o la deformazione del sottosuolo, dal 2017 l’INGV è stato incaricato dal MiTE (ex MiSE) di mettere in atto un sistema congiunto di monitoraggio geofisico, che oggi può essere considerato il più avanzato d’Italia per il settore.

To constrain seismic anisotropy under and around the Alps in Europe, we study SKS shear wave splitting from the region densely covered by the AlpArray seismic network. We apply a technique based on measuring the splitting intensity, constraining well both the fast orientation and the splitting delay. Four years of teleseismic earthquake data were processed, from 723 temporary and permanent broad-band stations of the AlpArray deployment including ocean-bottom seismometers, providing a spatial coverage that is unprecedented. The technique is applied automatically (without human intervention), and it thus provides a reproducible image of anisotropic structure in and around the Alpine region. As in earlier studies, we observe a coherent rotation of fast axes in the western part of the Alpine chain, and a region of homogeneous fast orientation in the Central Alps. The spatial variation of splitting delay times is particularly interesting though. On one hand, there is a clear positive correlation with Alpine topography, suggesting that part of the seismic anisotropy (deformation) is caused by the Alpine orogeny. On the other hand, anisotropic strength around the mountain chain shows a distinct contrast between the Western and Eastern Alps. This difference is best explained by the more active mantle flow around the Western Alps. The new observational constraints, especially the splitting delay, provide new information on Alpine geodynamics. © 2021 The Author(s) 2021. Published by Oxford University Press on behalf of The Royal Astronomical Society.

The rapid ongoing climate change, its driving mechanisms and its environmental, economic and societal implications in the mid to long-term time scales are among the most debated issues within the environmental scientific community today. Albeit the increasing effort made in recent years to understand the complex dynamics of climate change both at national and international level, the degree of comprehension of the behavior of the Earth system as a whole is far from being considered satisfactory. The technological and scientific means available today and the integration of different disciplines offer the possibility to study climate in a multifaceted and manifold way, so that a single specific issue may be approached from different perspectives, resulting in a better focus of the entire problem. MACMAP, a Strategic Department Project of INGV started in October 2020, aims to study the climate change in the Polar and Mediterranean regions by extending and integrating existing data with new observations, modelling outputs and qualitative information from the recent past to near future scenarios (Figure 1). The project follows a multidisciplinary approach involving transboundary expertise from different scientific fields: from atmospheric science to oceanography and hydrology, from space to sea level studies, from seismological to geochemical sciences. In particular, several different open issues are addressed: ● the impact of climate change on the ocean circulation; ● how climate change affects the deep ocean processes; ● the evolution of sea level rise from the recent past to the near future (up to 2100); ● the chemical composition of the sea as a proxy of climate change; ● how climate change affects the isotope composition of meteoric water; ● the relation between the ionized atmosphere and climate change; ● the impact of atmospheric forcing on the cryosphere, which is rapidly changing in response to global warming. Such a diversity of topics and science backgrounds implies a dedicated effort to an optimized and efficient data management, following international standards in compliance with FAIR principles to ensure open data access and interoperability. Beside the scientific targets, this project represents an important attempt to reduce the fragmentation of Research by creating strong synergies among different expertise and thematic

In data 27 Ottobre 2017 si è verificato un evento sismico di Mw 4 con epicentro a Montesano sulla Marcellana (Basilicata), ad una distanza di meno di 10 km dal bordo esterno della concessione idrocarburi Val d'Agri (VA). Trattandosi di un terremoto localizzato al di fuori del Dominio Esteso di monitoraggio (Indirizzi e Linee Guida del MiSE), la rilevanza di tale evento e possibili nessi con le attività di produzione di Oil&Gas non erano stati approfonditi. Considerando che nel passato la Val d'Agri e il Vallo del Diano sono stati colpiti da eventi con magnitudo superiore a M>6.5, è utile studiare terremoti moderati nell'area in oggetto, ai fini di contribuire a migliorare la caratterizzazione della pericolosità sismica, potenzialmente distruttiva. Approfittando della presenza di un elevato numero di stazioni sismiche operative nell'area della VA e dintorni, analizziamo i parametri sorgente del l'evento principale Mw 4, applicando tecniche sismologiche avanzate per stimare le incertezze associate all'inversione del momento tensore (MT) e per identificare plausibili effetti di direttività. Il MT è dominato da un meccanismo di faglia normale, orientato in direzione NW-SE, con una profondità ipocentrale del centroide di 14 km. L'unico aftershock registrato (ML 2.1) è stato usato come funzione di Green empirica, ai fini di calcolare la funzione temporale apparente della sorgente (ASTF - apparent source time function) dell'evento principale. Durate apparenti in un range tra 0.11 -- 0.21 s (derivate da onde-S) definiscono un pattern azimutale, che indica una rottura asimmetrica bilaterale, con 70% della propagazione in direzione N310$\,^{\circ}$W, suggerendo un piano di rottura immergendo verso sudovest. I nostri risultati evidenziano che il terremoto di Mw 4 a Montesano sulla Marcellano ha attivato un segmento di faglia più profondo, vicino al basamento, eventualmente associato con l'Eastern Agri Fault System. Il basso potenziale di trigger (meno del 10%) provocato dallo stress associato all'esaurimento del giacimento, rende improbabile la possibilità di un evento indotto o innescato per via dell'estrazione trentennale di idrocarburi dal reservoir VA e suggerisce piuttosto un'origine naturale provocato da stress tettonico locale.

On October 27th, 2017, a Mw 4 earthquake occurred close to the municipality of Montesano sulla Marcellana, less than 10 km external to the concession of the largest European on-shore hydrocarbon reservoir - the Val d'Agri oilfield (Southern Italy). Being a weak event located outside the extended monitoring domain of the industrial concession, the relevance of this earthquake and possible links with the hydrocarbon exploitation were not deepened. The study of weak to moderate earthquakes can improve the characterization of the potentially destructive seismic hazard of this particular area, already struck by M>6.5 episodes in the past. Taking advantage of a wide coverage of seismic stations deployed in the VA region, we analyze the source parameters of this Mw 4 earthquake applying advanced seismological techniques to estimate the uncertainties derived from the moment tensor inversion and identify plausible directivity effects. The moment tensor is dominated by a NW-SE oriented normal faulting with a centroid depth of 14 km. A singleML 2.1 aftershock was recorded and used as empirical Green function to calculate the apparent source time function for the mainshock. Apparent durations (in the range 0.11 - 0.21 s, obtained from S-waves) define an azimuthal pattern which reveals an asymmetric bilateral rupture with the70% of the rupture propagation in the N310$\,^{\circ}$W direction, suggesting a rupture plane dipping to the SW. Our results conclude that the Montesano earthquake activated a deeper fault segment associated to the Eastern Agri Fault System close to the basement. The relative low trigger potential below 10% based on depletion-induced stress changes discards an induced or triggered event due to the long-term hydrocarbon extraction in the Val d'Agri oilfield, and it rather suggests a natural cause due to the local tectonic stress.

On October 27, 2017, an Mw 4 earthquake occurred close to the municipality of Montesano sulla Marcellana, less than 10 km external to the concession of the largest European onshore hydrocarbon reservoir—the Val d’Agri oilfield (Southern Italy). Being a weak event located outside the extended monitoring domain of the industrial concession, the relevance of this earthquake and the possible links with the hydrocarbon exploitation were not extensively discussed. Actually, the analysis of shallow seismic events close to subsurface exploitation domains plays a significant role in the definition of key parameters in order to discriminate between natural, triggered, and induced seismicity, especially in tectonically active regions. The study of weak-to-moderate earthquakes can improve the characterization of the potentially destructive seismic hazard of this particular area, already struck by M > 6.5 episodes in the past. In this work, we analyze the source parameters of this Mw 4 earthquake by applying advanced seismological techniques to estimate the uncertainties derived from the moment tensor inversion and identify plausible directivity effects. The moment tensor is dominated by a NW–SE oriented normal faulting with a centroid depth of 14 km. A single ML 2.1 aftershock was recorded and used as the empirical Green’s function to calculate the apparent source time function for the mainshock. Apparent durations (in the range 0.11–0.21 s, obtained from S-waves) define an azimuthal pattern, which reveals an asymmetric bilateral rupture with 70% of the rupture propagation in the N310°Wdirection, suggesting a rupture plane dipping to the SW. Our results tally with the activation of a deeper fault segment associated with the Eastern Agri Fault System close to the basement as the origin of the Montesano earthquake. Finally, the Coulomb stress rate induced by depletion of the oilfield is calculated to quantify the trigger potential estimated for the Montesano earthquake yielding relatively low probabilities below 10%. Our analyses point toward the conclusion that the Mw 4 event was more likely due to the local natural tectonic stress, rather than induced or triggered by the long-term hydrocarbon extraction in the Val d’Agri oilfield.