Andrea Billi

• PhD
• Researcher at Italian National Research Council

In the pursuit of energy independence, security, and reducing greenhouse gas emissions, the world faces the challenge of transitioning to clean energy sources. To achieve the transition toward net-zero carbon emissions in the near-future, Italy set a National Plan for Recovery and Resilience (PNRR), in which 3.2 billion € are allocated for the rese...

The analysis of fault-related mineralization and, particularly, in the Fluid Inclusions (FIs) entrapped in synkinematic minerals are key to assess the origin and modalities of fluid circulation through fault zones. The results of these analyses, compared with those focusing on the present-day fluids, are crucial to better understanding the processe...

Hydrocarbon leakage from reservoirs poses significant environmental and societal problems, including the potential contamination of drinking water and agricultural soils. Distinguishing between natural and anthropogenic leakage is challenging but crucial for assessing human impacts on reservoir seal integrity and developing effective mitigation str...

Rough surfaces known as stylolites are common geological features that are developed by pressure solution, especially in carbonate rocks, where they are used as strain markers and as stress gauges. As applications are developing in various geological settings, questions arise regarding the uncertainties associated with quantitative estimates of pal...

Aiming at understanding the source of the fluids that mineralizing within seismically active fault zones, we investigate the noble gas isotopes (i.e., helium (He), neon (Ne), and argon (Ar)) in the fluid inclusions (FIs) trapped in the calcite veins sampled along high-angle fault zones of the Contursi hydrothermal basin, southern Italy. The latter...

Aiming at understanding the source of the fluids that mineralizing within seismically active fault zones, we investigate the noble gas isotopes (i.e., helium (He), neon (Ne), and argon (Ar)) in the fluid inclusions (FIs) trapped in the calcite veins sampled along high‐angle fault zones of the Contursi hydrothermal basin, southern Italy. The latter...

The two Mw > 7.5 earthquakes that struck the East Anatolian Fault (EAF), Türkiye, in 2023 caused more slip than expected, indicating that they were potentially part of a supercycle, in which the occurrence probability of a large earthquake is determined by accumulated strain rather than time since the last large earthquake. Here, we show two potent...

Understanding the factors that govern past fluid circulation in tectonically active and/or hydrocarbon-rich basins is crucial for elucidating present-day fluid-flow scenarios. We investigate the circulation of paleo-fluids in the extensional-transtensional Val d'Agri Basin (southern Italy), home to a giant oil field and significantly affected by bo...

Understanding the behavior of fluids in seismically active faults and their chemical-physical (dis)equilibrium with the host rock is important to understand the role of fluids upon seismicity and their possible potential for forecasting earthquakes. The small number of case studies where seismic and geochemical data are available and the lack of ac...

The Eastern Southern Alps fold‐and‐thrust belt (ESA) is part of the seismically active S‐verging retro‐wedge of the European Alps. Its temporal tectonic evolution during continental shortening has so far been constrained by few and low‐resolution indirect time constraints. Aiming at better elucidating the ESA spatiotemporal evolution, we gathered n...

The Val d’Agri Basin is a Quaternary sedimentary basin topping multiple tectonic units of the southern Apen nines fold-and-thrust belt and a giant oilfield within deeper Apulian Platform carbonates. This basin is bounded by the seismically active East Agri (EAFS) and Monti della Maddalena (MMFS) extensional fault systems. The reservoir rocks are...

Plain Language Summary A boundary between two plates is not a single line but it is often a large area with diffuse deformation, simultaneous tectonic processes and complex geodynamics. Here, we analyze the Africa‐Eurasia convergent and deformed boundary in southern Italy, central Mediterranean, where the lineaments along which crustal blocks move,...

The Po Plain (Italy) is one of the most densely populated and productive regions of Europe, characterized by a flourishing economy (also linked to strategic subsurface resources) and several world cultural and natural heritage sites. The coupling of socio-economic interests with geological hazards (i.e. seismic, subsidence, and flooding hazards) in...

Sr and Nd isotopic ratios along with (REE + Y) and other trace elements were measured in bedded travertines from three quarries at Tivoli Terme, Latium, aimed at deciphering their chemical and isotopic characteristics for the origin and evolution of uids. Travertines, which were deposited between ~81 and ~54 ka BP, display high Sr and low REY conte...

The Calabrian Orogenic Arc (COA) is affected by active extensional and strike-slip tectonics as documented by the presence of N-S and NE-SW trending intra-montane basins bordered by faults, whose slip has caused many destructive earthquakes during the last millennium. By focusing on the central sector of the COA (Sila Massif) through the analysis o...

The fast individuation and modeling of faults responsible for large earthquakes are fundamental for understanding the evolution of potentially destructive seismic sequences. This is even more challenging in case of buried thrusts located in offshore areas, like those hosting the 9 November 2022 Ml 5.7 (Mw 5.5) and ML 5.2 earthquakes that nucleated...

The evolution of the Apennine wedge has seen the time‐space migration of the forebulge, foredeep, thrust wedge, and back‐arc extension phases in the wake of the Eastward rollback of the subducting Adria slab. In this framework, thrusting and post‐orogenic extensional faulting have occurred in two parallel forelandward‐migrating ribbons, with extens...

Val d'Agri is a seismically active intermontane basin in southern Italy known for hosting the largest on-shore hydrocarbon reservoir in western Europe. Despite extensive study of the basin, important questions remain regarding fluid circulation and the possible link between deep hydrocarbon reservoirs, faults, natural and induced seismicity, and ga...

The central Apennines are a fold-thrust belt currently affected by post-orogenic ex- tensional seismicity. To constrain the influence that the inherited thrust-related structures exert on the present seismic behavior of the belt, we provide the high-resolution structural and hydraulic characterization of one of the most external exposed thrust faul...

The Po Plain (Italy) is one of the most densely populated and productive regions of Europe, characterized by a flourishing economy (also linked to strategic subsurface resources) and several world cultural and natural heritage sites. The coupling of social-economic interests with geological hazards (i.e., seismic, subsidence and flooding hazards) i...

Keywords: coseismic breccia CO 2 decompression earthquake gas expansion dolostone South Matese, Apennines, is a hydrothermally and seismically active extensional area characterized by CO 2 outgassing and Mw ≤ 7.1 earthquakes. There, meters-sized pockets of incohesive pulverized dolostone are hosted within Mesozoic carbonates at the hanging wall of...

In the western Mediterranean, following the intervening continent-continent collision, the subduction of the Tethyan ocean has progressively come to an end or almost in large sectors. Compressional deformation connected with the ongoing Africa–Eurasia convergence has therefore progressively resumed mostly along the southern passive margins of the M...

Post-orogenic back-arc magmatism is accompanied by hydrothermal ore deposits and mineralizations derived from mantle and crustal sources. We investigate Zannone Island (ZI), back-arc Tyrrhenian basin, Italy, to define the source(s) of mineralizing hydrothermal fluids and their relationships with the regional petrological-tectonic setting. On ZI, ea...

The microscale mechanisms of hydrocarbons movement along faults and fault zones, the potential carriers of hydrocarbons toward the productive geological traps, remain largely unknown. The majority of previous studies inferred the hydraulic behavior of faults with respect to hydrocarbon movements without providing meso and microstructural observatio...

Major advances in smartphones and tablets in terms of their built-in sensors (esp. cameras), available computational power and on-board memory are transforming the role of such devices into the key digital platform around which geological fieldwork is redesigning itself. This digital transition is changing how geoscientists collect and share multim...

Bedding-perpendicular joints striking parallel (longitudinal) and perpendicular (transverse) to both the axis of the hosting anticline and the trend of the foredeep-belt system are widely recognized in fold-and-thrust belts. Their occurrence has been commonly attributed to folding-related processes, such as syn-folding outer-arc extension, although...

Knowing water quality at larger scales and related ground and surface water interactions impacted by land use and climate is essential to our future protection and restoration investments. Population growth has driven humankind into the Anthropocene where continuous water quality degradation is a global phenomenon as shown by extensive recalcitrant...

The reconstruction of the hydrocarbon migration and entrapment history is fundamental for reducing risks and identifying traps and migration pathways during oil exploration and exploitation in fold-and-thrust belts, which host 14% of the world's discovered oil reserves. Within fold-and thrust belts, faults and folds have a fundamental role in contr...

The Tyrrhenian back‐arc basin developed at the rear of the E‐ward migrating Apennine fold‐and‐thrust belt, with northward decreasing rollback of the subducting Adria slab leading to northward fading of back‐arc extension. The northern portion of the Tyrrhenian basin is made of thinned continental crust, whereas in the central/southern portion exten...

Since the advent of affordable consumer-grade cameras over a century ago, photographic images have been the standard medium for capturing and visualizing outcrop-scale geological features. Despite the ubiquity of raster image data capture in routine fieldwork, the development of close-range 3D remote-sensing techniques has led to a paradigm shift i...

The Mt. Gorzano Fault (MGF) is a major seismically active extensional fault of the central Apennines, responsible for the destructive Mw 6.0 Amatrice earthquake in 2016. The MGF developed during post-orogenic extensional tectonics, generating a continental basin in the hanging wall. The age of the onset of the MGF and the relationship among faultin...

Seismological data recorded in the Ionian Sea by a network of seven Ocean Bottom Seismometers (OBSs) during the 2017–2018 SEISMOFAULTS experiment provides a close-up view of seismogenic structures that are potential sources of medium-high magnitude earthquakes. The high-quality signal-to-noise ratio waveforms are observed for earthquakes at differe...

During earthquakes, fault rupture can involve multiple segments in synchronous or cascade mechanisms, leading to an increasing magnitude of the mainshock or rate of aftershocks. Since the seismogenic portions of faults are inaccessible, studying the geometrical and mechanical interaction between exhumed fault segments can contribute to the understa...

Hydrogeochemical changes before Mw ≥ ∼5.0 earthquakes are hoped to be applicable as seismic precursors. It is now necessary to pass from single experiences to structured networks, systematically monitoring large seismic areas for long periods. Our aim is to provide a pilot methodological experience for how such networks could be realized and the ty...

We analysed temporal variations of trace element concentrations in groundwater from a 101 m-deep borehole (HA01) in northern Iceland during 2010–2018 and compared them with seismic and volcanic events that occurred in the same period to identify potential hydrogeochemical precursors. An increase of B, Al, V, Li and Mo concentrations started from ei...

Available online xxxx Editor: A. Webb Keywords: seismic precursors normal fault slip zone coseismic deformation fluids Mt. Morrone fault Fluids play an important role in seismic faulting both at hypocentral depths during earthquake nucleation and at shallower crustal levels during rupture propagation. Pre-to co-seismic anomalies of crustal fluid ci...

This study aims at assessing the deformation processes affecting an area NW of the city of Ravenna (northern Italy), caused by groundwater withdrawal activities. In-situ data, geologic and structural maps, piezometric measurements, underground water withdrawal volumes, and satellite C-band SAR data were used to jointly exploit two different techniq...

The Calabrian Arc subduction-rollback system along the convergent Africa/Eurasia plate boundary is among the most active geological structures in the Mediterranean Sea. However, its seismogenic behaviour is largely unknown, mostly due to the lack of seismological observations. We studied low-to-moderate magnitude earthquakes recorded by the seismic...

We combined structural data collected in the field and those obtained from a virtual outcrop model constructed from drone imagery, to perform Discrete Fracture Network (DFN) modelling and to characterize the fracture distribution within the damage zone of the low-displacement (∼50 m) carbonate-hosted Pietrasecca Fault (PF) (central Apennines, Italy...

The inner Apennines (Italy) are characterized by scattered outcrops of continent‐derived orogenic metamorphic units exposed along the Tyrrhenian coast from northern to southern Apennines. At least since the 1970s, some peculiar rocks exposed on Zannone Island (central Italy) have been described as the only Paleozoic‐Triassic metamorphic complex lin...

Active faults within the southern Apennines fold-and-thrust belt modulate the present-day upwelling of hydrothermal fluids at surface. In the Monte Alpi area, we investigated the structural and geo-morphological settings of ∼10 km²-wide area, and texture and stable isotope composition of Quaternary travertine deposits to identify the present day fa...

The Adria microplate is the foreland of the oppositely verging Apennines and Alps or Dinarides fold‐thrust belts associated to the related subduction zones. Along its western margin, the Adria plate hosts the active Northern Apennines accretionary prism, which is buried under the Adriatic Sea and the Po Plain. The interpretation of seismic reflecti...

Geotagged smartphone photos can be employed to build digital terrain models using structure from motion-multiview stereo (SfM-MVS) photogrammetry. Accelerometer, magnetometer, and gyroscope sensors integrated within consumer-grade smartphones can be used to record the orientation of images, which can be combined with location information provided b...

Chemical and physical responses of groundwater to seismicity have been documented for thousands of years. Among the waves produced by earthquakes, Rayleigh waves can spread to great distances and produce hydrogeological perturbations in response to their passage. In this work, the groundwater level, which was continuously recorded in a monitoring w...

We report the results of a multiproxy study that combines structural analysis of a fracture–stylolite network and isotopic characterization of calcite vein cements and/or fault coating. Together with new paleopiezometric and radiometric constraints on burial evolution and deformation timing, these results provide a first-order picture of the region...

Anomalies in Radon (222Rn) concentrations prior to earthquakes have been widely documented in seismogenic areas worldwide, but questions about their predictability remain largely unanswered. Even if it is not universally accepted, the analysis of the high-resolution time series of Rn (222Rn) concentrations in groundwater, air and soil has been prop...

The SEISMOFAULTS project (www.seismofaults.it) was set up in 2016 with the general plan of exploring the seismicity of marine areas using deep seafloor observatories. The activity of the first two years (Seismofaults 2017 and 2018) consisted of the installation of a geophysical-geochemical temporary monitoring network over the Ionian Sea floor. Ele...

We report the results of a multi-proxy study that combines structural analysis of fracture-stylolite network and isotopic characterization of calcite vein cements/fault coating. Together with new paleopiezometric and radiometric constraints on burial evolution and deformation timing, these results provide a first-order picture of the regional fluid...

Numerous studies exist on exhumed tectonic mélanges along subduction channels whereas, in accretionary wedge interiors, deformation mechanisms and related fluid circulation in tectonic mélanges are still underexplored. We combine structural and microstructural observations with geochemical (stable and clumped isotopes and isotope composition of nob...

Pleistocene (bedded) travertines from Acquasanta Terme display ranges of Sr and (REE + Y) contents (462–1576 mg/kg and 250–13,789 ng/g, respectively), which are consistent with an evaporitic rock source. PAAS-normalized (REE + Y) patterns may support the origin of travertine-bearing fluids from marine rocks. Travertines exhibit a very narrow range...

Fault inversion may lead to significant obliteration of earlier tectonic structures, thus preventing the straightforward interpretation of the complete kinematics and deformation history of faults. We adopt a multidisciplinary approach to: (1) reconstruct the tectonic evolution through space and in time of the extensionally-inverted Mt. Tancia Thru...

We defined deformation mechanisms and syn-tectonic fluid circulation within the Mt. Massico intra-wedge tectonic mélange, developed at depths <5 km and at maximum burial temperature of 140 °C, located in the inner part of the Apennines fold-and-thrust belt, Italy. This mélange developed at the base of a heterogeneous clastic succession, characteriz...

An understanding of the origin and migration pathways of geofluids in an active seismic area is of paramount importance in terms of societal challenges such as mitigation of seismic hazards. This study investigates the relationship between the stable isotope ratio 13C/12C of deep CO2 and geothermometry in selected groundwater samples located close...

Zannone is a very important island, located in the Neogene-Quaternary extensional domain of the Tyrrhenian back-arc basin, as it is the unique spot where the Paleozoic (?) crystalline basement is hypotesized to be exposed in central Apennines. The exposure of such hypothetical basement in the Zannone Island is very problematic as it implies very la...

The Apennines chain is an active Neogene fold-and-thrust belt resulting from the westward subduction of the Adriatic microplate. Starting from the end of the Early Pleistocene, the chain was affected by an increase in regional uplift. Recent GPS data resolved uplift rates of 1–2 mm/yr for the whole Apennines, whereas, in the Adriatic flank, several...

Faults have grooves that are formed by abrasion and wear during slip. Recent observations indicate that this grooving is only a large-scale feature, indicating brittle behavior has a length scale limit. The connection between this scale and earthquake behavior remains limited because no examples exist from a proven seismogenic fault. Here, we addre...

Empirical scaling relationships between fault or slip dimensions and earthquake magnitudes are often used to assess the maximum possible earthquake magnitude of a territory. Upon the assumption of the reactivability of any fault, the earthquake magnitudes derived from the surface fault length (FLEM) are compared at the national scale in Italy again...

The nucleation and concentration of asbestos in rocks are mostly associated with mechanisms of fibre formation, combined with the water-dependent mineralogical alteration produced during the serpentinization of ultramafic masses. Very little is known about the structural settings and tectonic histories that influence and control the occurrence of a...

The Ionian Sea in southern Italy is at the center of active interaction and convergence between the Eurasian and African–Adriatic plates in the Mediterranean. This area is seismically active with instrumentally and/or historically recorded Mw>7.0 earthquakes, and it is affected by recently discovered long strike-slip faults across the active Calabr...

The 2016 Mw ≥ 6.0 Amatrice-Norcia earthquakes (central Apennines, Italy) and the related seismic sequence were associated with increases in arsenic and vanadium concentrations recorded in groundwater springs a few months before the earthquakes occurred. To evaluate these signals as reliable seismic precursors and effective predictive tools, we stud...

The Mt. Massico ridge (central southern Apennines, Italy) is characterized by a ~150‐m‐thick tectonic mélange located at the base of a Tortonian‐lower Messinian heterogeneous clastic succession consisting of layered sandstones, limestones, marls, and claystones with intercalated mass wasting deposits and isolated olistoliths, which deposited above...

The Ionian Sea in southern Italy is at the center of active interaction and convergence between the Eurasian and African-Adriatic plates in the Mediterranean. This area is seismically active with instrumentally/historically-recorded Mw > 7.0 earthquakes and it is affected by recently-discovered long strike-slip faults across the active Calabrian ac...

Themogene travertine deposits are continental CaCO3 precipitates deriving from Ca(HCO3)2-rich geothermal fluids (waters) that flow and spring in thermally active areas such as near active or quiescent volcanoes (Pentecost, 2005). The dateability of most travertine deposits (i.e., those younger than 500–800ka through U-series radiometric methods), t...

Solid Earth Discussion paper available at https://www.solid-earth-discuss.net/se-2018-98/

Understanding natural variations of Rn (²²²Rn) concentrations is the fundamental prerequisite of using this radioactive gas as a tracer, or even precursor, of natural processes, including earthquakes. In this work, Rn concentrations in groundwater were continuously measured over a seven-month period, during 2017, in the Giardino Spring, Italy, toge...

The Western Ionian Sea is an area of great interest from the seismological point of view due to the occurrence of the highest magnitude earthquakes which affected the Italian territory in historical and recent times, followed in some cases by violent tsunamis (e.g. 1193, M 6.6; 1693, M 7.4; 1908, M 7.2; 1990, M 5.7). Although these earthquakes have...

A seismic sequence in central Italy from August 2016 to January 2017 affected groundwater dynamics in fractured carbonate aquifers. Changes in spring discharge, water-table position, and streamflow were recorded for several months following nine Mw 5.0–6.5 seismic events. Data from 22 measurement sites, located within 100 km of the epicentral zones...

A seismological and geochemical experiment, also accompanied by a detailed bathymetric survey, is now ongoing in the Ionian Sea from May 2017. Eight Ocean Bottom Seismometers and Hydrophones (OBS/H) and two modules for geochemical monitoring (CH4, CO2 and O) were deployed on the sea bottom (www.seismofaults.it).

Seismic precursors are an as yet unattained frontier in earthquake studies. With the aim of making a step towards this frontier, we present a hydrogeochemical dataset associated with the 2016 Amatrice-Norcia seismic sequence (central Apennines, Italy), developed from August 24 th , with an M w 6.0 event, and culminating on October 30 th , with an M...

The environmental recovery of quarried areas is increasingly a landscaping first-order issue in many countries and relevant lessons can be learned from each case history, depending upon factors such as the terrain nature and landscape consolidation over time. The case of the Tivoli travertine quarries near Rome (Acque Albule Basin, Italy) is addres...

Abstract: In this multi-methodological study, microstructural observations of fault rocks are combined with micromechanical property analyses (Contact Resonance Atomic Force Microscopy, CR-AFM) and with rotary friction experiments (SHIVA apparatus) to find evidence of seismic to aseismic slip and understand the nanoscale rheology of clay-bearing, c...

Many earthquakes propagate up to the Earth’s surface producing surface ruptures. Seismic slip propagation is facilitated by along-fault low dynamic frictional resistance, which is controlled by a number of physico-chemical lubrication mechanisms. In particular, rotary shear experiments conducted at seismic slip rates (1 ms−1) show that phyllosilica...

An integrated investigation including geological, geomorphological, geophysical and structural survey, tephra analyses, ¹⁴C and ⁴⁰Ar/³⁹Ar dating, as well as paleoseismic trenching along the N-Matese fault system is presented. The study allowed the characterization of the tectonic mobility of this structure as well as the associated Bojano basin sed...

This study is the first documentation of syn-diagenetic non-tectonic contractional deformations observed in two Pleistocene thermogene travertine deposits from the late Miocene-Pleistocene Tuscan extensional-hydrothermal province (Italy). The deposits consist of primary porous beds hosting secondary bed-parallel carbonate veins. The porous beds are...

Image-based 3D modeling has recently opened the way to the use of virtual outcrop models in geology. An intriguing application of this method involves the production of orthorectified images of outcrops using almost any user-defined point of view, so that photorealistic cross-sections suitable for numerous geological purposes and measurements can b...

This paper presents the preliminary results of a multidisciplinary study to determine a possible hydrogeological survey methodology to be applied in the seismic field. In fact in case of earthquakes, variations of the stress involving a migration of fluids occur, with consequent changes in the flow and geochemistry of groundwater. For this reason,...

We document phyllosilicates occurrence along five shallow (exhumed from depths < 3 km) carbonate-hosted extensional faults from the seismically-active domain of the central Apennines, Italy. The shallow portion of this domain is characterized by a sedimentary succession consisting of ∼5–6 km thick massive carbonate deposits overlain by ∼2 km thick...

___________________________________________________________________________ The occurrence of phyllosilicate-­‐rich layers and phyllosilicate-­‐rich fault rocks has been documented and studied, for the first time, in five shallow (exhumed from depths < 3 km) carbonate-­‐hosted extensional fault zones from the seismically-­‐active central Apennines,...

We examine the potentially-seismic right-lateral transtensional–extensional Tre Monti Fault (central Apennines, Italy) with structural and geochemical methods and develop a conceptual evolutionary model of extensional faulting with fluid involvement in shallow (≤3 km depth) faults in carbonate rocks. In the analysed fault zone, multiscale fault roc...

Changes in groundwater levels related to earthquake have been investigated throughout the world, but most studies have focused on the effects of one large earthquake. The aim of this study was to identify potential patterns of level changes in response to several earthquakes, and possible variations of ion concentrations, gas compositions and isoto...

In this study we show for the first time how quantitative stress estimates can be derived by combining calcite twinning and stylolite roughness stress fingerprinting techniques in a fold-and-thrust belt. First, we present a new method that gives access to stress inversion using tectonic stylolites without access to the stylolite surface and compare...

The seismic cycle is accompanied by stress perturbations that possibly accelerate at the end of the interseismic period, just before the earthquake. Stress modification determines fluids migration. Therefore, changes in the flow and geochemistry of groundwater prior to an earthquake may be expected. In fact, hydrologic effects of strain during and...

The Neogene–Quaternary Albegna basin (southern Tuscany, central Italy), located to the south of the active geothermal field of Monte Amiata, hosts fossil and active thermogene travertine deposits, which are used in this study to reconstruct the spatio-temporal evolution of the feeding hydrothermal system. Travertine deposition is controlled by regi...

Structural and geochemical methods applied to the seismically-active extensional Tre Monti Fault (central Apennines, Italy) were used to develop a conceptual evolutionary model of seismic faulting with fluid involvement for shallow (≤ 3 km depth) extensional faults in carbonate rocks. The relative chronology of these structures was reconstructed th...