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Up to now, the complexity and the uncertainty in defining the extent down-dip and along-strike of active faults led to the elaboration of several methods to establish structure 3D geometry. Therefore, different approaches produce different scenarios of seismogenic rupture for the same active tectonic structure. Here we investigate two active fault systems of the central Apennines of Italy: the Roveto Valley Fault and the Laga Mts. Fault. We specifically aim to the understanding of along-strike segmentation of these tectonic structures to contribute to improve the knowledge of the seismotectonic setting of the central Apennines. Overall, our goal is to make a step forward toward the comprehension of the wide theme of seismogenic fault segmentation. The main uncertainties regarding the two fault systems are different. In the case of the Roveto Valley Fault, the uncertainty is twofold: 1) the current activity of the fault is debated; according to some authors, fault activity ended during the Middle Pleistocene, whereas others suggest the fault is still active and seismogenic; 2) the extent of the proposed active section of this tectonic structure is not clearly defined, and this is relevant in a seismotectonic perspective. The Laga Mts. fault system is a complex tectonic structure whose activity is well geologically documented for the southern section of the system; moreover, the fault system played a key role in the seismogenic process of the 2016-2017 central Italy earthquake sequence. Some authors interpret the fault as the surface expression of a single large seismogenic source, capable of generating seismic events of Mw ≈ 6.7. Other authors, instead, propose that this system consists in two structurally aligned but kinematically independent faults, the Amatrice and Campotosto faults. Following the 2016-2017 seismic sequence, an important debate is taking place within the scientific community about the definition of 1) the individual seismogenic sources that make up the Laga Mts. fault system and 2) the geometric and kinematic relationship between the fault(s) at surface and its (their) possible prolongation at depth as crustal major seismogenic sources. Through morphological, morphotectonic and structural analyses we propose segmentation criteria and possible segmentation scenarios for these two structures. These allow us to estimate the maximum coseismic rupture and the maximum magnitude expected from a single seismic event for the investigated fault, improving the seismotectonic knowledge of the central Apennines.

SUMMARYThe preparation, initiation and occurrence dynamics of earthquakes in Italy are governed by several frequently unknown physical mechanisms and parameters. Understanding these mechanisms is crucial for developing new techniques and approaches for earthquake monitoring and hazard assessments. Here, we develop a first-order numerical model simulating quasi-static crustal interseismic loading, coseismic brittle episodic dislocation and post-seismic relaxation for extensional and compressional earthquakes in Italy based on a common framework of lithostatic and tectonic forces. Our model includes an upper crust, where the fault is locked, and a deep crust, where the fault experiences steady shear.The results indicate that during the interseismic phase, the contrasting behaviour between the upper locked fault segment and lower creeping fault segment generates a stretched volume at depth in the hangingwall via extensional tectonics while a contracted volume forms via compressional tectonics. The interseismic stress and strain gradients invert at the coseismic stage, with the interseismic dilated volume contracting during the coseismic stage, and vice versa. Moreover, interseismic stress gradients promote coseismic gravitational subsidence of the hangingwall for normal fault earthquakes and elastic uplift for reverse fault earthquakes. Finally, the post-seismic relaxation is characterized by further ground subsidence and uplift for normal and reverse faulting earthquakes, respectively, which is consistent with the faulting style. The fault is the passive feature, with slipping generating the seismic waves, whereas the energy activating the movement is stored mostly in the hangingwall volume. The main source of energy for normal faulting and thrust is provided by the lithostatic load and elastic load, respectively.

The Seismic Microzonation, as practiced in Italy, consists in defining microzones of the territory affected by homogeneous response to seismic ground shaking, defined as stable zones, vulnerable seismic amplification zones, and unstable zones. In detail, the unstable zones are affected by landslides, soil liquefaction, ground subsidence and surface faulting. In this framework, we conducted a study in the administrative district of L’Aquila (central Italy) aimed at the construction of a new school building, in an area indicated as prone to surface faulting (an active and capable fault was hypothesised in the area) and liquefaction.We dug two trenches (named as A and B) perpendicular to the presumed active fault trace. The excavation walls exposed several different continental units mainly characterized by colluvial, organic-rich and “cultural” sediments, as well as paleosols. In trench A, some units, made of sandy-gravelly colluvial deposits, contained abundant pottery fragments, being intensely reworked by very recent human activity. These units were mainly composed of silt and sand sparse with carbonate clasts and directly overlying Middle Pleistocene alluvial deposits. Trench B only exposed units containing pottery fragments and hence pertaining to historical times. Several radiocarbon dating made on charcoal found within these units confirmed the recent age of the deposits, spanning from 25000 to 1800 years before the present. The analysis of the trench walls, the analysis of two boreholes, and field geological investigations revealed the absence of any surface faulting events affecting the stratigraphic sequence of the area, at least since the Middle Pleistocene, likely since the Early Pleistocene. Furthermore, trench B exposed several sedimentary dikes reaching up close to the ground surface, crossing the historical colluvial units, as well as other deformation features typical of liquefaction phenomena. The radiocarbon age determination and the sedimentological characteristics of the units indicate that the most recent liquefaction event occurred after 180 A.D.Ultimately, this work represents a “best-practice” case study to investigate the occurrence of geological surface criticalities (such as surface faulting and liquefaction) at specific sites of interest.

Surface faulting is, together with strong ground shaking, a hazard associated with major earthquake faults. Assessing surface faulting potential of a given active tectonic structure is a fundamental prerequisite to adequately plan the use of territories and to perform new constructions, in order to act practices aimed to mitigate the associated risk. Assessing the surface faulting potential represents also ground for correctly performing re-construction and retrofitting of buildings and infrastructures during post-earthquake activities. We investigated a branch of a major seismogenic normal fault in the central Apennines of Italy, the Campi-Preci fault, along which the monumental Sant’Eutizio Abbey is located. The medieval Abbey is one of the most important cultural/religious edifices of the central Apennines, heavily damaged by the MW 6.5 October 30, 2016, earthquake, focused a few km to the south. Our study, based on field geological, geomorphological and structural survey and trenching investigations revealed that I) the trace of the Campi-Preci active fault branch is not actually located where presently reported in the available literature, II) the supposed morpho-tectonic features (basically, some km-long scarp carved on the Meso-Cenozoic carbonate bedrock), that suggested the presence of the fault segment in the area of the Sant’Eutizio Abbey, are not related to the active fault but are probably associated to a presently inactive reverse fault and III) the Sant’Eutizio Abbey is likely not potentially affected by primary surface faulting. Our work highlights that only a comprehensive multidisciplinary approach allows to correctly assess surface faulting potential in both seismotectonic and engineering perspectives.

The Castelnuovo village is placed on a small NW-SE trending ridge, approximately 60 m higher than the valley floor, occupying a portion of the larger continental L'Aquila Basin (Central Italy). During the April 6, 2009 L'Aquila earthquake (Mw 6.3), the village suffered heavy damage. Several studies investigated the local seismic amplification of the Castelnuovo area employing geotechnical, geophysical, and geological surveys, together with 1D, 2D and 3D numerical models. However, all these studies relied on shallow geotechnical and geophysical surveys, which do not reach the engineering bedrock and do not constrain the presence of an impedance contrast at depth. To date, no detailed study has been carried out to assess the depth of the engineering bedrock. In this work, we fill this gap by executing two deep boreholes reaching the engineering bedrock, tied with an extensive campaign of microtremor measurements all over the Castelnuovo ridge and the surrounding plain. The interpretation of such new data, together with analytical, numerical, and geostatistical techniques, demonstrates that local seismic amplification is linked to a strong impedance contrast at more than 200-m depth beneath the Castelnuovo village associated with the lithological transition between clayey silts and breccias. Such results differ from those provided by previous studies, where such impedance contrast was considered shallower, and represent a milestone for assessing the local seismic hazard of the area.

Assessing seismic site effects is essential in earthquake hazard studies. Local seismic amplification is strongly related to the site stratigraphy and topography, the dynamic properties of the subsoil deposits, and the earthquake features. The evaluation of these factors is mandatory to achieve a consistent model of the seismic hazard at small scale. Here we discuss the case of Castelnuovo village (L’Aquila, central Italy). Located on a small ridge, approximately 60 m higher than the valley floor, the village was heavily struck by April 6, 2009, Mw 6.3 L’Aquila earthquake, with catastrophic collapse of several buildings. Previous studies ascribed the observed damage to the presence of shallow caves beneath the buildings or to the topographic amplification.In this work, an updated and detailed subsoil model for Castelnuovo site has been provided, based updated geological surveys, such as borehole logs and geophysical data consisting in microtremor measurements and down-hole.These measurements identified resonant frequencies occurring in the range of 0.7-3.0 Hz. These frequency peaks are related to the presence of a velocity contrast at depth between the San Nicandro silts and the Madonna della Neve breccias, as indicated by the performed deep boreholes. Thanks to analytical, numerical, and geostatistical techniques, we identified the main impedance contrast at approximately 210 m depth from the top of the hill, much deeper than previous studies. These new findings allowed to create an accurate and consistent subsoil model summarized by two geological cross-sections of the Castelnuovo ridge, showing that the seismic site effects at the Castelnuovo village are mainly related to stratigraphic amplification.

Although several observations have been reported in the literature before a strong earthquake, their relation with the forthcoming event is often controversial. Since many physical processes and parameters govern the dynamics of preparation, initiation, and occurrence of earthquakes, their understanding is essential for explaining anomalous seismological, geophysical, hydrological and geodetic signals before a strong earthquake that may be considered for seismic monitoring and hazard assessment. In this work, the interseismic and coseismic stress and strain fields associated with the 6 April 2009, Mw 6.3 L'Aquila earthquake are calculated via a 3D numerical model designed to simulate the crustal interseismic loading and the coseismic brittle episodic dislocation along the fault. The model adopts a framework of gravitational and tectonic forces that are compatible with the geodynamics of the Central Apennines region of the Italian territory. The model assumes a brittle upper crust, where the fault has stick-slip behaviour, and a plastic deeper crust, where the fault is in stationary creep. The results indicate that the concurrent action of gravitational and tectonic forces determines steep interseismic stress gradients at the transition between the creeping and locked fault planes that promote the coseismic subsidence of the hanging wall. The interseismic strain above the transition between that locked upper fault and its unlocked lower shear zone develops a dilated volume in the hanging wall and a contracted volume in the footwall. These stress and strain variations are compatible with seismological, geophysical and geodetic anomalies observed before the earthquake, i.e., Vp/Vs anomalies and location of foreshocks. Interseismic stress and strain patterns invert during the coseismic stage. The dilated volume, formed during the interseismic phase, will be contracted at the coseismic stage and, conversely, the footwall volume previously contracted will be expanded.

Una ricostruzione geologica tridimensionale dell'area colpita dal terremoto dell'Italia centrale Sono stati pubblicati online e resi fruibili liberamente a tutta la comunità scientifica i risultati del Progetto RETRACE-3D (centRal italy EarThquakes integRAted Crustal model), che ha investigato il volume crostale in cui si è generato il terremoto di Amatrice del 24 agosto 2016 e la successiva sequenza sismica; un'area di circa 2.500 km2, a cavallo tra Lazio, Abruzzo, Umbria e Marche, interessata da oltre 118.000 eventi sismici tra il 2016 e il 2019. Il modello geologico 3D e il Rapporto finale sono il prodotto della collaborazione di più di 60 ricercatori ed esperti del Dipartimento della Protezione Civile e degli istituti di ricerca CNR-IGAG, CNR-IREA, INGV e ISPRA-Servizio Geologico d'Italia, Centri di Competenza che operano nel Servizio Nazionale della Protezione Civile. Al Progetto hanno inoltre collaborato Eni e Total, soggetti privati anch'essi parte del Servizio Nazionale della Protezione Civile, che hanno reso disponibili dati di sottosuolo e know-how. Il modello geologico 3D consente di mettere in evidenza la distribuzione e la geometria, nonché la complessità delle relazioni reciproche, delle più rilevanti unità geologiche e delle faglie principali, comprese quelle sismogeniche, fino a una profondità superiore a 10 km, riconciliando gli elementi osservati in superficie con le strutture in profondità. Il Rapporto finale e il modello geologico 3D sono rilasciati con licenza CC-BY 4.0, garantendo la possibilità di essere liberamente utilizzati per studi alla scala regionale con il riconoscimento della corretta attribuzione. Download dei risultati (http://www.retrace3d.it/contenuti.html) RETRACE-3D Central Italy Geological Model (2021). doi: 10.13127/retrace-3d/geomod.2021 RETRACE-3D Working Group (2021). RETRACE-3D: centRal italy EarThquakes integRAted Crustal modEl. Rapporto finale. Eds. INGV, ISPRA, CNR-IGAG, DPC. Roma, pp. 100. doi: 10.5281/zenodo.4604940

In the last decades, satellite monitoring techniques allowed to discover non-catastrophic slope movements triggered by earthquake shaking and involving deep blind sliding surfaces of old paleo-landslides. Understanding the triggering and attenuation mechanisms of such mass movements is crucial to assess their hazard. On December 2018, the Etna volcano (southern Italy) began a very intense eruption, accompanied by a seismic swarm with magnitudes up to 4.9. Synthetic Aperture Radar data from Sentinel-1 and ALOS-2 identified some local displacements over a hilly area to the southwest of the Etna volcano, near Paternò village. We evaluated the contribution of seismically-induced surface instabilities to the observed ground displacement by employing a multidisciplinary analysis comprising geological, geotechnical and geomorphological data, together with analytical and dynamic modelling. The results of our study allowed us to identify the geometry and kinematics of a previously unknown paleo-landslide. A pseudostatic, limit-equilibrium back-analysis of the landslide mass highlighted that the displacements detected by InSAR data were caused by the undrained seismic instability of the landslide mass, which was dormant before the volcanic eruption, under the light-to-moderate seismic shacking of the December 26, Mw 4.9 earthquake. Such a new observation allowed to identify the geometry and kinematics of a previously unknown landslide mass and confirms that earthquakes have a cumulative effect on landslides that doesn't necessarily manifest as a failure but could evolve in a catastrophic collapse after several earthquakes. Such an aspect must be adequately investigated to identify unknown quiescent landslide bodies and to prevent the effects of their potential collapse during an earthquake.

Earthquakes are the result of the strain accumulation in the earth's crust over a variable decade to millennial period, i.e., the interseismic stage, followed by a sudden stress release at a crustal discontinuity, i.e., the coseismic stage, finally evolving in a postseismic stage.Commonly, the seismic cycle is modelled with analytical and numerical approaches. Analytical methods simulate the interseismic, coseismic and postseismic phases independently. These models impose the slip of single or multiple planar sources to infer fault geometry, slip distribution and regional deformations to fit the available geodetic or seismological measurements, often regardless of the magnitude and orientation of the interseismic gravitational and tectonic forces. Numerical approaches allow simulating complex geometries in heterogeneous media and at different modelling scales, assuming various constitutive laws. Such models often impose the slip on the fault plane to simulate the observed coseismic dislocation or the propagation of the seismic waves, or they adopt ad-hoc boundary conditions to investigate the interseismic stress accumulation or the postseismic relaxation for specific cases.We contribute to the understanding of the seismic cycle associated to a single fault by developing a numerical model to simulate the long-term crustal interseismic deformation, the coseismic brittle episodic dislocation, and the postseismic relaxation of the upper crust within a unified environment for both normal and reverse fault earthquakes in Italy, including the forces acting during the interseismic period, i.e., the lithostatic load and the horizontal stress field, the latter simulated with the application of a shear traction a the model’s base. We adjusted the setup of our model to simulate the interseismic, coseismic and postseismic phases for two seismic events: the Mw 6.1 L’Aquila 2009 normal fault earthquake and the Mw 5.9 Emilia-Romagna 2012 reverse fault earthquake.The simulation results show that the applied basal shear traction is fundamental to model the large-scale interseismic pattern since it allows for a first-order simulation of the ongoing crustal interseismic extension of the Central Apennines and compression of the Adriatic foreland and the north-eastern part of the Italian territory. The action of shear tractions and lithostatic forces generates a local concentration of stresses and strains in the presence of local heterogeneities or discontinuities, i.e., at the transition between the brittle locked fault and the ductile unlocked slipping fault during the interseismic stage. Such an interseismic strain partitioning provides maximum horizontal stress sufficient to exceed the friction on the locked brittle part of the fault, with the subsequent collapse of the hangingwall in case of extensional earthquakes or the expulsion of the hangingwall in case of compressional earthquakes. The instantaneous slip of the hangingwall perturbs the crustal pore fluid pressures, triggering groundwater flow in the postseismic phase from regions of higher pore pressures, which further compress, to regions of lower pore pressures, which further dilate. As a result, displacements gradually accumulate in the postseismic phase, according to the dissipation of pore pressure excess. Once the postseismic phase terminates, a new cycle of interseismic loading can start again.

Seismic amplifications are dictated by the depth of the bedrock and the stratigraphy and dynamic properties of the soil deposits. Quantifying these properties, together with their uncertainty, is a necessary task to perform a reliable assessment of the seismic risk at an urban scale. In this paper, a multidisciplinary analysis is presented, where information of different nature is combined. Borehole logs, geophysical, geological and geotechnical surveys are interpreted with the aid of analytical, numerical and geostatistical techniques to characterise the complex shape of the bedrock and the linear dynamic properties of the sedimentary deposits filling the Cassino basin, a Quaternary intermontane basin located in central Italy. The regional and local seismic hazard is firstly identified with geological surveys that reveal an active seismogenic fault capable of producing earthquakes with estimated magnitudes up to 6.7–6.8. Boreholes reaching depths variable up to a maximum of 180 m and microtremor measurements, revealing the sharp impedance contrast at the transition between the sedimentary/arenaceous bedrock and the soft Quaternary infilling, are combined to identify the depth of the bedrock and the linear dynamic properties of soil deposits. These are one of the key factors governing the propagation to the ground level of seismic waves, and their assessment represents the first step for the seismic hazard characterisation of the plain.

Study area Venafro Mts., southern-central Italy, Mediterranean basin. Study focus Via a collection of geological and hydrogeological data, a flow conceptual model of a carbonate aquifer has been coupled with a numerical model via MODFLOW code and Unsaturated Zone Flow (UZF) package in steady state and transient conditions. Simulation is further implemented with different management scenarios, for facing possible emergencies due to recharge decrease, also simulating a drastic water abstraction cut-off. New hydrological insights for the region Carbonate fractured aquifers are a strategic water resource in the whole Mediterranean area, supplying major metropolitan areas. Despite these huge extensions, such groundwater systems are threatened by increasing drought occurrence and significant human water abstraction. A characterization of a carbonate fractured aquifer (370 km2) located in central-southern Italy has been performed. Venafro Mts. Aquifer (VMA) hosts a strategic resource for the Western Campania Waterworks (WCW) that supplies the populous metropolitan area of Naples, with 3.8 million inhabitants. VMA shows a slow response, with recovery time estimated at the decennial scale, testifying its limited resilience to natural and human pressures. A shift is proposed from passive management to a more comprehensive concept of smart-water monitoring, applied not only to waterworks and pipelines, but also to groundwater resources in the environment.

The involvement of fluids in the earthquake cycle is a still open debate in the scientific community (e.g. Gratier et al., 2002). In the last years, new data from laboratory experiments and on-field discrete and continuous monitoring of soil gas, springs and gas vents were gathered worldwide (e.g. Martinelli, 2015; Nielsen et al., 2016). The aim of these studies was to better define the role of the observed fluid changes either as a trigger of earthquakes or as the co and post-seismic response to the transient (dynamic) and permanent (static) stress changes. This subject is particularly attractive in central and southern Apennines (Italy), where both huge water and CO2 circulation at depth, occur (e.g Frondini et al., 2018). In this respect, the three long-lasting earthquake sequences that hit central Apennine in the last decades (1997, 2009 and 2016-2017, Mw up to 6.5) were accompanied by hydrological (increase or decrease in the spring discharges) and hydrochemical (variations in chemical composition, physico-chemical parameters) anomalies (e.g. Carro et al., 2005; Barberio et al., 2017; Petitta et al., 2018). Changes were observed mainly in the co and post-seismic phase and only a few pre-seismic signals were recorded. Temporal monitoring ranged from weeks to months, but higher sampling rates are needed to study crustal deformation processes (stress and volumetric strain) during the earthquake cycle. For example, since 2015 De Luca et al. (2016, 2018) are been performing high frequency (up to 20 samples/second) continuous monitoring of temperature, hydraulic pressure, and electrical conductivity in the Gran Sasso aquifer. They recorded unambiguous long-term (days to months) pre-Amatrice earthquake anomalies in both hydraulic pressure and electrical conductivity, related to its preparation stage.In the light of the above, we decided to duplicate the equipment presently working in the Gran Sasso aquifer in a site with similar hydrological setting: the Venafro carbonate hydrostructure (Molise, Saroli et al., 2019). The site we chose is located in one of the most seismically active sectors of central-southern Apenninic belt, repeatedly hit in the past by large magnitude earthquakes and crossed by up to 20 km-long extensional fault systems (e.g. Galli & Naso, 2009). The main goals of our research are: i) measuring and understanding the dynamics of the carbonate aquifer, also through the analysis of rainfall, ii) deepening the relationships between aquifer behavior and earthquakes as well as to iii) widen the monitored areas.Our experimental equipment includes a 3-channels 24-bit ADC set up for continuous local recording in groundwater (De Luca et al., 2016, 2018) in a horizontal borehole located in the drainage gallery “San Bartolomeo”, managed by Campania Aqueduct company. We started data acquisition in May 2019 by high-frequency continuous sampling (20 Hz for each channel) of physical parameters such as groundwater hydraulic pressure, temperature and electrical conductivity. We present some preliminary results (elaborated through a statistical approach) and possible explanations regarding the hydraulic pressure signals recorded before and during nearby (Mw 4.4, distance ~ 45 km) and regional (Albania, Mw 6.2, distance ~ 400 km) earthquakes, both occurred in November 2019.

A sustained increase in spring discharges was monitored after the 2016 Central Italy seismic sequence in the fractured carbonate aquifer of Valnerina–Sibillini Mts. The groundwater surplus recorded between August 2016 and November 2017 was determined to be between 400 and 500 × 106 m3. In fractured aquifers, the post-seismic rise in spring discharges is generally attributed to an increase in bulk permeability caused by the fracture cleaning effect, which is induced by pore pressure propagation. In the studied aquifers, the large amount of additional discharge cannot only be attributed to the enhanced permeability, which was evaluated to be less than 20% after each main seismic event. A detailed analysis of the spring discharge hydrographs and of the water level at five gauging stations was carried out to determine the possible causes of this sudden increase in groundwater outflow. Taking into account the geological and structural framework, a conceptual model of a basin-in-series has been adopted to describe the complex hydrogeological setting, where the thrusts and extensional faults have clearly influenced the groundwater flow directions before and after the seismic sequence. The prevalent portion of the total post-seismic discharge surplus not explained by the increase in permeability has been attributed to changes in the hydraulic gradient that caused seismogenic fault rupture and the disruption in the upgradient sector of the aquifer. The additional flow calculated through the breach of the pre-existing hydrostructural barrier corresponds to approximately 470 × 106 m3. This value is consistent with the total discharge increase measured in the whole study area, validating the proposed conceptual model. Consequently, a shift in the piezometric divide of the hydrogeological system has been induced, causing a potentially permanent change that lowers the discharge amount of the eastern springs.

In the recent decades, satellite monitoring techniques have enhanced the discovery of non-catastrophic slope movements triggered by earthquake shaking involving old paleo-landslides with deep-seated sliding surfaces. Understanding the triggering and attenuation mechanisms of such mass movements is crucial to assessing their hazard. In December 2018, Etna volcano (southern Italy) began a very intense eruption, which was accompanied by a seismic swarm with magnitudes reaching 4.9. Synthetic aperture radar data identified local displacements over a hilly area to the west of Paterno village. We evaluated the contribution of seismically induced surface instability to the observed ground displacement by employing a multidisciplinary analysis comprising geological, geotechnical and geomorphological data, together with analytical and dynamic modelling. The results allowed us to identify the geometry and kinematics of a previously unknown paleo-landslide, which was stable before the volcanic eruption. The landslide was triggered by the light-to-moderate seismic shaking produced by the strongest event of the seismic sequence, namely, the December 26, Mw 4.9 earthquake. This observation confirms that seismic shaking has a cumulative effect on landslides that does not necessarily manifest as a failure but could evolve into a catastrophic collapse after several earthquakes.

During the 2012 Emilia-Romagna (Italy) seismic sequence, several time-dependent phenomena occurred, such as changes in the groundwater regime and chemistry, liquefaction, and postseismic ground displacements. Because time-dependent phenomena require time-dependent physical mechanisms, we interpreted such events as the result of the poroelastic response of the crust after the mainshock. In our study, we performed a two-dimensional poroelastic numerical analysis calibrated with Cosmo-SkyMed interferometric data and measured piezometric levels in water wells. The simulation results are consistent with the observed postseismic ground displacement and water level changes. The simulations show that crustal volumetric changes induced by poroelastic relaxation and the afterslip along the mainshock fault are both required to reproduce the amplitude (approximately 4 cm) and temporal evolution of the observed postseismic uplift. Poroelastic relaxation also affects the aftershock distribution. In fact, the aftershocks are correlated with the postseismic Coulomb stress evolution. In particular, a considerably higher fraction of aftershocks occurs when the evolving poroelastic Coulomb stress is positive. These findings highlight the need to perform calculations that adequately consider the time-dependent poroelastic effect when modeling postseismic scenarios, especially for forecasting the temporal and spatial evolution of stresses after a large earthquake. Failing to do so results in an overestimation of the afterslip and an inaccurate definition of stress and strain in the postseismic phase.

A hydrogeological conceptual model has been developed that describes the hydrothermal system of Suio Terme (central Italy). The studied area is located along the peri-Tyrrhenian zone of the central Apennines, between the Mesozoic and Cenozoic carbonate platform sequences of the Aurunci Mountains and the volcanic sequences of the Roccamonfina. A multi-disciplinary approach was followed, using new hydrogeological surveys, the interpretation of stratigraphic logs of boreholes and water wells, and geophysical data—seismic sections, shear-wave velocity (Vs) crustal model and gravimetric model. The collected information allowed for construction of a conceptual hydrogeological model and characterization of the hydrothermal system. The Suio hydrothermal system is strongly influenced by the Eastern Aurunci hydrostructure. Along the southeastern side, the top of the hydrostructure sinks to −1,000 m relative to sea level via a series of normal faults which give origin to the Garigliano graben. Geological and hydrogeological data strongly suggest the propagation and mixing of hot fluids, with cold waters coming from the shallow karst circuit. The aquitard distribution, the normal tectonic displacements and the fracturing of the karst hydrostructure strongly influence the hydrothermal basin. Carbon dioxide and other gasses play a key role in the whole circuit, facilitating the development of the hydrothermal system. The current level of knowledge suggests that the origin of the Suio hydrothermalism is the result of interaction between the carbonate reservoir of the Eastern Aurunci Mountains and the hot and deep crust of this peri-Tyrrhenian sector, where the Roccamonfina volcano represents the shallowest expression.

The rapid and uncontrolled evolution of urban and industrial settlements often turns to be unsustainable for the natural and anthropic system. A prominent example is the subsidence induced by intensive groundwater exploitation. Assessing the risk produced on urban agglomerations by the groundwater table drawdown enables to visualize the impact and to undertake policies that protects structures, infrastructures and, more generally, the socio-historical-cultural environment of the cities. This task implies to assemble hydrological, hydrogeological and geotechnical factors into comprehensive models that lead to compute free field deformation. Interfacing this effect with the mechanical characteristics of buildings or infrastructures allows to quantify damage severity. The present paper reports a study carried out for the city of Bologna, one of the most emblematic examples in Italy, whose old town and suburbs have undergone an extensive and continuous subsidence from the early seventies. An integrated risk assessment methodology is implemented defining the paramount factors, intensity measures, engineering demand parameters, vulnerability and exposure and building an interpretative model based on observation.

The Sorrentina Peninsula is a densely populated area with high touristic impact. It is located in a morphologically complex zone of Southern Italy frequently affected by dangerous and calamitous la...

We provide new field data from geologic mapping and bedrock structural geology along the western side of the Matese Mts in central Italy, a region of high seismicity, strain rates among the highest of the entire Apennines (4–5 mm/yr GPS-determined extension), and poorly constrained active faults. The existing knowledge on the Aquae Iuliae normal fault (AIF) was implemented with geometric and kinematic data that better constrain its total length (16.5 km), the minimum long-term throw rate (0.3–0.4 mm/yr, post-late glacial maximum, LGM), and the segmentation. For the first time, we provide evidence of post-350 ka and possibly late Quaternary activity of the Ailano – Piedimonte Matese normal fault (APMF). The APMF is 18 km long. It is composed of a main 11 km-long segment striking NW–SE and progressively bending to the E–W in its southern part, and a 7 km-long segment striking E–W to ENE-WSW with very poor evidence of recent activity. The available data suggest a possible post-LGM throw rate of the main segment of ≳0.15 mm/yr. There is no evidence of active linkage in the step-over zone between the AIF and APMF (Prata Sannita step-over). An original tectonic model is proposed by comparing structural and geodetic data. The AIF and APMF belong to two major, nearly parallel fault systems. One system runs at the core of the Matese Mts and is formed by the AIF and the faults of the Gallo-Letino-Matese Lake system. The other system runs along the western side of the Matese Mts and is formed by the APMF, linked to the SE with the Piedimonte Matese – Gioia Sannitica fault. The finite extension of the APMF might be transferred to the NW towards the San Pietro Infine fault. The nearly 2–3 mm/yr GPS-determined extension rate is probably partitioned between the two systems, with a ratio that is difficult to establish due to poor GPS coverage. The proposed model, though incomplete (several faults/transfer zones need further investigations), aids in the seismotectonic interpretation of poorly-known earthquakes (e.g., 346/355 AD earthquake on the Ailano – Piedimonte Matese – Gioia Sannitica fault system), and stimulates and further orients seismotectonic investigations aimed at constraining the segmentation pattern and seismogenic potential of the area.

We investigated the contribution of earthquake-induced surface movements to the ground displacements detected through Interferometric Synthetic Aperture Radar (InSAR) data, after the Mw 3.9 Ischia earthquake on 21 August 2017. A permanent displacement approach, based on the limit equilibrium method, allowed estimation of the spatial extent of the earthquake-induced landslides and the associated probability of failure. The proposed procedure identified critical areas potentially affected by slope movements partially overlapping the coseismic ground displacement retrieved by InSAR data. Therefore, the observed ground displacement field is the combination of both fault slip and surficial sliding caused by the seismic shaking. These findings highlight the need to perform preliminary calculations to account for the non-tectonic contributions to ground displacements before any estimation of the earthquake source geometry and kinematics. Such information is fundamental to avoid both the incorrect definition of the source geometry and the possible overestimation of the coseismic slip over the causative fault. Moreover, knowledge of the areas potentially affected by slope movements could contribute to better management of a seismic emergency, especially in areas exposed to high seismic and hydrogeological risks.