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The accurate characterization of microearthquake sequences allows seismologists to shed light on the physical processes involved in earthquake nucleation, the deformation processes underlying rupture activation and propagation, and to image faults geometry at depth. The current methodologies used for this purpose first need the event detection and the phase-picking - usually manual-based - and earthquake locations, which require plenty of work even by expert analysts particularly in the case of microearthquake signals, commonly noise contaminated. Thus, improving standard procedures through semi-automatic or fully-automatic workflows would be an essential step forward towards the more efficient analysis of seismic sequences.Here we show the results of a semi-automated template matching and machine-learning based workflow applied for the characterization of the foreshock-mainshock-aftershock microearthquake sequence occurred close to Castelsaraceno village (High Agri Valley, Southern Apennines, Italy) in August 2020. The analyses were performed on seismic data mainly recorded by a local seismic network belonging to the High Agri Valley geophysical Observatory (HAVO) deployed in the study area and located at a maximum epicentral distance of ~20 km from the seismicity cluster.The application of the semi-automated single-station template matching technique to the continuous data-streams of the two nearest stations of the HAVO network (from 28th July to 12th October 2020) allowed us to detect more than twice the number of microearthquakes previously identified by standard manual detections. The phase-picking was automatically performed through a deep-learning algorithm (Phasenet) on the 202 ultimate detected microearthquakes. Finally, an automatic multi-step absolute and relative earthquake location procedure was carried out.A total of 76 events were identified as belonging to the Castelsaraceno sequence, which occurred in a short time span (7-12 August) and in a limited range of depths (10 -12 km). Both the Ml 2.1 foreshock doublet and the Ml 2.9 mainshock occurred on 7 August ruptured the same seismogenic patch, thus suggesting the presence of a persistent asperity. The integrated analysis of the aftershocks distribution, the focal mechanism of the mainshock, and the geological framework of the study area, allowed revealing the seismogenic fault, not currently mapped in literature: a NE-SW striking (225°), high-angle (55°) fault with a left-lateral transtensional (rake -30°) kinematic. We also hypothesize that the seismic sequence occurred at depth in a brittle layer of the crystalline basement confined between two regions with more ductile rheology; futhermore, the estimated b-value (0.73±0.04) indicates the occurrence of the sequence in a relatively low-heterogeneity material and suggests the unimportant effect of pore-fluid pressure in driving its evolution.

Seismo-electromagnetic signals are electromagnetic signals generated by the propagation of a seismic wave in a porous media containing fluids (Gao & Hu, 2010).These signals can potentially provide useful information on the poro-elastic media and the hosted fluids (Garambois & Dietrich, 2002).Thus, there has been a growing interest in the study of SES in recent years, due to their potential.Researchers are focusing both on modelling and analysis of both passive and active experiments to investigate the characteristics of these signals (e.g. Honkura et al., 2000; Matsushima et al., 2002; Warden et al., 2013; Gao et al., 2016; Balasco et al., 2014; Dzieran et al., 2019).Passive experiments involve the observation and analysis of naturally occurring SES triggered by earthquakes, while active experiments involve the controlled generation of these signals using seismic source.The aim of our work is to present the results deriving from the analysis of SES recorded with both approaches. As for the passive one, the data set consists of the time series recorded by two magnetotelluric stations in continuous monitoring, co-located with two seismic stations, in seismically active areas of Southern Italy (the Gargano promontory and the Agri valley).As for the active one, the data set derives by an active seismic experiment carried out in the caldera of the Phlegrean Fields, the Italian super-volcano.

Over the last decades, many studies highlighted the close relationship between thermal structure, surface processes, and tectonic forces in controlling the deformation of the lithosphere. The contribution of these key factors, however, is not constant in time and may result in a complex deformation history, as already observed in many regions around the globe. In this view, the rheology of the crust is pivotal to leading regional tectonic evolution.Among the factors that may cause remarkable strength and rheological variations in the crust, the presence of fluid phases is undoubtedly one of the most prominent. The mechanisms of rock-fluid interaction are still a debated field of research. However, it has been suggested in many studies that a major effect of fluids is enhanced seismicity of regions where they are present.In this framework, the Val d’Agri represents a perfect example of how crustal evolution can be influenced by several factors interacting with one another. In this region, we analyze the relationships between different mechanisms in the final structural setting of the region, with implications on the natural and induced seismicity. To this aim, we built up a numerical model that integrates the combined effects of rheological stratification of the crust, inherited zones of weakness, variations in the tectonic regime, surface erosion, and fluid presence. Our results show that variation in the strength of the evaporite layer between the carbonate platform and the basement has a profound impact on the tectonic style of the Val d’Agri. The uplifting and subsidence pattern in the region follows stages of slow vertical movements to stages of very fast uplifting and denudation, due to the activation of new tectonic structures where movement is enhanced. This reflects on pressure and temperature variations in time, that follow typical yo-yo patterns observed in several tectonically active regions. The present-day configuration of the VA is also influenced by the erosion rate. More in detail, a comparison between the observed structures in the area and our model’s results with varying erosion rates suggests that the VA has been subjected to medium to fast erosion during its evolutionary history. In addition, our model predicts the presence and orientation of faults where fluid percolation or injection at high pressure can generate clusters of microseismicity.

The High Agri Valley (HAV) is an intermountain basin, located in the axial zone of Southern Apennines. It is characterized by a very high seismic hazard, as testified by the 1857 MW 7 Basilicata earthquake and by the present widespread seismic activity as well. The strong seismogenic potential of the area is strictly related to the geologic evolution of the Apennines and in turn to its present complex tectonic configuration.In addition to the natural low-magnitude seismicity occurring therein, two anthropogenic seismicity clusters are documented, located NE and SW of the artificial Pertusillo lake, respectively: a) fluid-induced microseismic swarms due to the injection, through the Costa Molina 2 well, of the wastewater produced by the exploitation of the Val d’Agri oilfield; b) protracted reservoir induced seismicity (RIS) caused by the combined effects of the water table oscillations of the Pertusillo lake, of the regional tectonics and of the poroelastic/elastic stress due to aquifers in the carbonate rocks.In the recent past, the elastic properties of the target area have been thoroughly investigated through velocity tomography studies; nonetheless, the attenuation crustal features are to date almost completely unexplored. In our work we thus aim at starting to fill this scientific gap.We here present the preliminary results obtained by applying the coda attenuation method on the seismic dataset collected in the period 2001-2014 by the stations belonging to both the trigger-mode monitoring network managed by ENI Oil Company and the Italian National Seismic Network managed by INGV. The complete seismic catalogue consists of about 1800 earthquakes in the magnitude range Ml 0 – 3.3 recorded by an average number of 14 stations. We show the unprecedented Q-coda estimations in the area. This information, in the first order Born approximation, represents the total attenuation accounting for both the scattering (QS) and the intrinsic quality factor (Qi). The preliminary results retrieved in this study are intended to be the first step towards a complete comprehension of the attenuation properties in this area by including in the near future also the continuous data recorded by the recently installed dense seismic network belonging to the HAV geophysical Observatory (HAVO). The planned investigation will pave the way to the discrimination between the scattering effects and anelastic features acting on the seismic waves propagating within the seismogenic crust of the study area. In that way it will be possible to better identify structural discontinuities and to gain further insights into the role of fluids in the preparatory phase and nucleation of earthquakes in the HAV.

Reservoir-induced seismicity (RIS) related to water-level changes in artificial lakes is a well-documented phenomenon. The best known RIS example is the 6.3 Mw 1967 Koyna-Warna earthquake. However, it must be considered that small-to-moderate magnitude RIS occurs very often, both in relation to water load changes and poroelastic stress perturbation in pre-existing faults. Monitoring the temporal and spatial evolution of RIS is very important for assessing the mechanical state of faults, especially when artificial lakes are located in areas characterized by a high seismic hazard. Indeed, where the crust is affected by the presence of faults with a stress level close to failure, even static stress changes of a few tens of kPa associated with RIS might promote the worst-case scenario of large earthquakes.Understanding of the physical processes that generate and characterize natural and induced earthquakes, including RIS, is often improved by studying the spatiotemporal evolution of the source parameters obtained through inversion of the seismic data, or by studying the mechanical properties of rocks through seismic velocities. Nevertheless, the source parameters for small magnitude earthquakes such as stress-drop and seismic energy are difficult to estimate, are model-dependent, and, above all, are affected by large uncertainties. Alternatively, the variability of RIS source processes can be investigated by studying the temporal and spatial variability of the ground motion intensity (δBe).In this work, we investigate the spatiotemporal evolution of ground motion caused by RIS at the Pertusillo artificial lake in southern Italy. The area has a strong seismogenic potential, having been affected in the past by the 1857, Mw 7.0 Basilicata earthquake. We consider ∼1,000 microearthquakes that occurred from 2001 to 2018 and were recorded by a local network of nine seismic stations. The ground motion intensity associated with microseismicity allows us to identify two periods, each lasting approximately 2 years. They are characterized by a high rate of events but exhibit different source properties and spatial distributions. In the first period, the seismicity is spatially clustered close to the lake, on faults with different orientations and kinematics. In the second period, the seismicity is distributed along the Monti della Maddalena faults. Comparing the ground motion intensities of the two periods, we observe that events that occurred in the first period are associated with higher stress levels than others, in agreement with the b-values of the respective frequency-magnitude distributions. We compare the temporal evolution of the ground motion intensity with the rainfall and water levels measured at the artificial lake, as well as with the discharge of a ∼80 km distant spring, which is strictly controlled by climate trends. The results provide information about the regional processes acting on the southern Apennines. Our results show that the microseismicity is clearly associated with the Pertusillo artificial lake in the first period, whereas in the second period is a result of a combination of local effects due to water table oscillations of the lake itself, regional tectonics, and the poroelastic and elastic phenomena associated with carbonate rocks hosting aquifers.

Improving the capability of seismic network to detect weak seismic events is one of the timeless challenges in seismology: the greater is the number of detected and locatable seismic events, the greater insights on the mechanisms responsible for seismic activation may be gained. Here we implement and apply a single-station template matching algorithm to detect events belonging to the fluid-injection induced seismicity cluster located in the High Agri Valley, Southern Italy, using the continuous seismic data stream of the closest station of the INSIEME network. To take into account the diversity of waveforms, albeit belonging to the same seismic cluster, eight different master templates were adopted. Afterwards, using all the stations of the network, we provide a seismic catalogue consisting of 196 located earthquakes, in the magnitude range − 1.2 ≤ Ml ≤ 1.2, with a completeness magnitude Mc = − 0.5 ± 0.1. This rich seismic catalogue allows us to describe the damage zone of a SW dipping fault, characterized by a variety of fractures critically stressed in the dip range between ~ 45° and ~ 75°. The time-evolution of seismicity clearly shows seismic swarm distribution characteristics with many events of similar magnitude, and the seismicity well correlates with injection operational parameters (i.e. injected volumes and injection pressures).

In this article, a framework of building monitoring is developed and transient and permanent variations of the fundamental period of vibration caused by both damage and repair interventions are investigated. The buildings of the University of Ferrara (Emilia-Romagna Region, Northern Italy), struck by the 2012 Emilia seismic sequence, were monitored using both temporary and permanent equipment: the first one to perform ambient vibration tests and the second one to implement permanent real-time monitoring for earthquake recording. Three on-demand ambient vibration tests were performed at each floor of the buildings: the first dataset was acquired a few months before the mainshock occurred on 20 May 2012 ( ML = 5.9, 6.8 km depth and 30 km epicentral distance); the second was acquired right after the end of the sequence, when the building showed slight damage (degree 1 according to the European Macroseismic Scale 98); finally, the third dataset was acquired in 2016 after the repair intervention. The data analysis clearly documented the permanent drop of the first vibration frequency as a symptom of the damage and its partial recovery that followed the repairs. The permanent real-time monitoring system, despite the fact that it was implemented using low-cost sensors, provided an insight into the intra-event frequency variation, allowing in turn a preliminary damage assessment.

Tropospheric excess path delays afflict surface motion measurements when Ground-based SAR (GB-SAR) interferometry is adopted. In this work, we propose an adaptive frequency-domain methodology to estimate the atmospheric phase screen (APS) components using wrapped GB-SAR interferometric data pairs, thus avoiding any possible phase unwrapping mistake. The experimental results show that the developed technique can detect and compensate for tropospheric fluctuations found in steep mountain areas without using any external digital elevation model of the investigated area. The paper addresses the potential of the developed technique by applying it on a set of simulated data.

In the framework of the non-destructive structural health monitoring we have developed an innovative combination of remote and in situ geophysical techniques aimed at assessing the structural properties of the infrastructure (i.e. eigenfrequencies, equivalent viscous damping factors and related modal shapes) and its interactions with foundation soils both in static and dynamic conditions. We have applied and validated this approach on the Gravina bridge, a bow-string bridge located on outcropping calcarenites in the city of Matera (Southern Italy) that develops for 144 m along a single-span steel-concrete deck. The non-invasive, non-destructive and cost-effective seismic and electromagnetic techniques have been fine-tuned for a multi-sensing monitoring at a multi-scale and multi-depth levels (i.e. with different degrees of spatial resolution and different soil subsurface depths). The foundation soil characteristics have been evaluated by means of three high-resolution geo-electrical tomographies, one bi-dimensional seismic array processed through Extended Spatial Auto Correlation (ESAC) and two single station seismic noise measurements analyzed by means of Horizontal to Vertical Noise Spectral Ratio (HVNSR). The main structural characteristics of the bridge have been estimated through permanent and on-demand monitoring by using seismic and electromagnetic sensing. The great potential of this approach concerns the synergy, correlation and integration of different geophysical sensing to determine the main static and dynamic structures/infrastructures parameters and their interaction with soil. Moreover, the convergence of results obtained by different technologies and independent data sets constitutes a validation procedure of the presented approach.

An integrated geophysical approach using non-invasive, non-destructive, and cost-effective seismic and electromagnetic techniques has been implemented to recognize the static and dynamic properties (i.e. eigenfrequencies, equivalent viscous damping factors, and related modal shapes) of the Gravina Bridge and its interaction with foundation soils. The “Gravina” is a bow-string bridge located on outcropping calcarenites in the city of Matera (Southern Italy) and develops for 144 m along a steel-concrete deck. The foundation soil characteristics have been evaluated by means of three high-resolution geo-electrical tomographies, one Vs velocity profile, and two site amplification functions. The main structural characteristics of the bridge have been estimated through permanent and on-demand monitoring using seismic and electromagnetic sensing. The former consisted of accelerometers and velocimeters installed with different geometrical arrangements for permanent earthquake and on-demand ambient vibration test recordings. The electromagnetic sensing was realized by a microwave radar interferometer placed below the deck to measure the displacements of the whole scenario illuminated by the antenna beam providing a continuous mapping of the static and dynamic displacements of the entire target. Acquired data have been analyzed in both frequency and time-frequency domain with the aim to study the stationary and non-stationary response of the monitored bridge. These experimental campaigns allowed us to assess the robustness of the proposed approach and to set up the zero-time reference point of the bridge dynamic parameters.

We applied an integrated, non-invasive and non-destructive seismic and electromagnetic sensing for understanding the static and dynamic properties of the Gravina bridge and its interaction with foundation soils. The 'Gravina' is a bow-string bridge located in the city of Matera (Southern Italy) that extends for 144 m along a steel-concrete deck. For foundation soils characterization we executed 3 high-resolution geo-electrical tomographies, 1 bi-dimensional seismic array and two single station seismic noise measurements. The main structural characteristics of the bridge were evaluated through seismic and electromagnetic sensing. The seismic sensing was carried out with four accelerometers and twelve velocimeters (standard and low cost sensors) installed with different geometrical arrangement for real-time and on-demand ambient noise recordings, vibration tests and earthquake recordings. The electromagnetic data have been collected by placing the IBIS-S system below the deck of the bridge. Acquired data have been analyzed in frequency domain with the aim to evaluate the eigenfrequencies and equivalent viscous damping factors.

This work proposes a method for estimating and compensating the atmospheric phase screen (APS) in sets of synthetic aperture radar (SAR) interferograms generated with a ground-based SAR (GB-SAR) instrument. We address the presented approach's physical, statistical, and mathematical framework by discussing its potential and limitations. In contrast with other existing algorithms that estimate the APS from the unwrapped phase signals, our methodology is based on the straightforward analysis of the wrapped phases, directly. Therefore, the method is not affected by any potential phase unwrapping mistake, and it is suitable for multitemporal interferometric SAR (InSAR) applications. The effects of the local topography, the decorrelation noise, and the ground deformation on the APS estimates are deeply studied. Experiments performed on simulated and real GB-SAR InSAR data corroborate the validity of the theory. In particular, the simulated results show that the method is beneficial in zones with medium-to-high topographic slopes (e.g., for Alpine and mountainous regions).

Summary We here present an innovative engineering and geophysical approach for the structural dynamic assessment of civil infrastructures, such as bridges. To this purpose, expeditive, cost-effective, non-invasive and non-destructive remote and in situ sensing techniques were adopted. Their pertinence to the aim of our study was tested on the Gravina Bridge, Southern Italy, a bow-string bridge which was opened to the vehicular circulation in 2016. Therefore, a twofold aim was pursued: 1) to validate the presented approach; 2) to provide an initial characterization of the dynamic properties of this infrastructure and to investigate its possible interaction with its base isolation system and foundation soils. The subsoil properties of the shallowest layers were evaluated through three high resolution resistivity tomographies, 1 bi-dimensional seismic array and two single station seismic noise measurement. The main structural features of the Gravina Bridge, that is its eigenfrequencies, the related damping factors and mode shapes, were retrieved by adopting both seismic and electromagnetic techniques. The collected, independent, data were analyzed by means of several processing techniques, in both frequency and time domain, which provided consistent results. These allowed us to confirm the reliability of estimations of dynamic properties and to validate the proposed approach.

A geophysical approach, based on the integration of satellite differential interferometric SAR technique and in situ geoelectrical and seismic methods, was applied with the aim to characterize a portion of urban area of Avigliano (PZ) town in Basilicata Region (southern Italy) affected by ground instability phenomena. Satellite analysis helped to discriminate areas of the town affected by superficial deformations and to monitor the dynamic behaviour of the structures located in these areas. Results from geoelectrical and seismic (active and passive) methods were compared with direct data (stratigraphic) and were interpreted with the aim to reconstruct the geometry of the subsoil. The joint application of both in situ techniques allowed the overcoming of the specific limits of each method and to improve the poor quality of the data due to the noise conditions typical of measurements carried out in urban areas. A preliminary geophysical model of the subsoil was obtained. The geophysical contrasts highlighted the presence of lithological discontinuities due to the superficial deformation processes that are affecting the portion of the investigated urban area. All the information has been transferred to the public administration technicians involved in the mitigation of hydrogeological risk in Basilicata Region.

The increasingly intensive use of natural resources with consequent environmental impacts has generated numerous social conflicts over the years, for whose solution it is necessary to build up an innovative territorial governance model based on sustainable and resilience thinking. At the international level, the problems associated with oil and gas extraction activities have been tackled by recognizing scientific research as a strategic role aimed at guaranteeing a more in-depth knowledge of environmental issues, the creation of collaboration networks between the various stakeholders and the whole usability of environmental data. This article presents the commitment made by the National Research Council of Italy - Institute of Methodologies for Environmental Analysis - CNR-IMAA to make the Val d'Agri community, an area affected by mining activities, less vulnerable and more resilient. Through the combined use of different scientific research methodologies, a multidisciplinary approach was developed which contributed to increasing the overall knowledge of the environmental problems of Val d'Agri as well as providing concrete indications for the development of more effective territorial management tools. Other activities, complementary to those of research, were aimed at ensuring correct and detailed environmental data information and communication and a broaden participation and involvement of citizens.

Civil infrastructures (i.e bridges, galleries ...) are crucial parts of the road asset and their possible degradation, with related consequences, may have great social, economical and safety impacts. On these grounds, the periodic monitoring of such infrastructures, from a static and dynamic point of view, is required for identifying possible changes in the structure properties, in order to prevent serious damages and disasters.In this study we propose an integrated geophysical approach by using non-invasive and non-destructive seismic and electromagnetic techniques with standard and low-cost sensors. It has been implemented to understand the static and dynamic properties of the Gravina bridge and its interaction with foundation soils. Gravina Bridge is a bow-string bridge located few km far from Matera (Southern Italy) and developing for 144 m along a steel-concrete deck. First, the properties of the foundation soils were studied by carrying out three high-resolution geo-electrical tomographies, one bi-dimensional seismic array and two single-station seismic noise measurements. Then, the structural characteristics of the bridge were inferred through seismic and electromagnetic sensing. The former was performed by means of recordings by accelerometers and velocimeters. The accelerometers were installed in a continuous acquisition mode, along the deck and on the top of the arch. In that way, several local and regional earthquakes were recorded and detected. The velocimeters were deployed along different seismic array configurations for on-demand ambient noise recordings, in normal traffic conditions and during vibration tests. The latter were executed by using vehicles as dynamic sources.The electromagnetic sensing was performed by using the Microwave Radar Interferometer: it was placed below the deck to measure the displacements of all the scenario illuminated by the antenna beam providing a continuous mapping of the static and dynamic displacements of the entire target.The acquired dataset was analyzed both in frequency and time-frequency domain in order to characterize the stationary and non-stationary response of the monitored bridge in terms of fundamental frequencies of vibration, equivalent viscous damping factors and modal shapes. The consistency between the results retrieved by different geophysical techniques provides therefore an importan hint about the reliability of the described approach.

Normalized cross-correlation of effective functions was originally developed to differentiate induced and natural seismicity. We apply this methodology to data sets acquired during hydraulic stimulation of shale gas to study temporal relationship between seismicity and the injection. Delays of seismicity induced by hydraulic fracturing are compared with delays of seismicity related to changes of the water level in a dam. A new observation is made; we show that seismicity induced by hydraulic fracturing and measured by the normalized cross-correlation can have very positive to even short negative delay after the injection. We explain this observation by rapid decline of induced seismicity after decrease of injection. On the contrary, we show that the seismicity triggered by water impounding in a dam is characterized by longer delays due to much greater distance between lake and the induced seismicity. We show how it is possible to measure the delay by the cross-correlation methodology despite periodicity of the signals.

Due to the deep socioeconomic implications, induced seismicity is a timely and increasingly relevant topic of interest for the general public. Cases of induced seismicity have a global distribution and involve a large number of industrial operations, with many documented cases from as far back to the beginning of the twentieth century. However, the sparse and fragmented documentation available makes it difficult to have a clear picture on our understanding of the physical phenomenon and consequently in our ability to mitigate the risk associated with induced seismicity. This review presents a unified and concise summary of the still open questions related to monitoring, discrimination, and management of induced seismicity in the European context and, when possible, provides potential answers. We further discuss selected critical European cases of induced seismicity, which led to the suspension or reduction of the related industrial activities.

This study discusses the effect of buildings vibrations in the urban field in the context of local seismic response studies in order to evaluate the possible occurrence of double resonance effects during strong-motions. The aim is to recognise the interaction effect between near surface geology and all overlying buildings in the urban area of the city of Matera (southern Italy). Single station seismic ambient noise measurements (230) were performed on the main lythologies (134) and on the principal building typologies (96). Soil and building measurements allowed estimating the main frequencies and relative amplitudes of the soil fundamental peaks as well as the first vibrational frequency of buildings. The period-height linear relationship, derived by experimental results, made it possible estimating the fundamental frequency for all the Matera's buildings. Having also estimated the frequencies at each point of the urban soil it was thus possible to obtain a soil-building resonance map in the linear elastic domain. Matera represents an important case study because the first vibration frequency for most of the buildings is quite close to those of the foundation soils. About 21% of buildings show high probability of occurrence of soil-building resonance effect, about 63% of the buildings are characterised by a medium resonance level, while about 16% are at zero or very low level. The proposed approach makes it also possible to identify the areas of the city characterised by these different probabilities of resonance levels.

In August 2016, a magnitude 6.0 earthquake struck Central Italy, starting a devastating seismic sequence, aggravated by other two events of magnitude 5.9 and 6.5, respectively. After the first mainshock, four Italian institutions installed a dense temporary network of 50 seismic stations in an area of 260 km2. The network was registered in the International Federation of Digital Seismograph Networks with the code 3A and quoted with a Digital Object Identifier (10.13127/SD/ku7Xm12Yy9). Raw data were converted into the standard binary miniSEED format, and organized in a structured archive. Then, data quality and completeness were checked, and all the relevant information was used for creating the metadata volumes. Finally, the 99 Gb of continuous seismic data and metadata were uploaded into the INGV node of the European Integrated Data Archive repository. Their use was regulated by a Memorandum of Understanding between the institutions. After an embargo period, the data are now available for many different seismological studies., Measurement(s)seismic activity • signal conversion functionTechnology Type(s)Sensor • Digitizer DeviceFactor Type(s)locationSample Characteristic - LocationItaly Machine-accessible metadata file describing the reported data: 10.6084/m9.figshare.9693602

The High Agri Valley is a tectonically active area in southern Italy characterized by high seismic hazard related to fault systems capable of generating up to M=7 earthquakes (i.e., the 1857 Mw 7 Basilicata earthquake). In addition to the natural seismicity, two different clusters of induced microseismicity were recognized to be caused by industrial operations carried out in the area: (1) the water loading and unloading operations in the Pertusillo artificial reservoir; (2) the wastewater disposal at the Costa Molina 2 injection well. The twofold nature of the recorded seismicity in the High Agri Valley makes it an ideal study area to deepen the understanding of nucleation processes of both natural and anthropogenic earthquakes and to improve the current methodologies for the discrimination between natural and induced seismic events by collecting high quality seismic data. Here we present the dataset gathered by the INSIEME seismic network that was installed in the High Agri Valley within the SIR-MIUR research project INSIEME (INduced Seismicity in Italy: Estimation, Monitoring, and sEismic risk mitigation). The seismic network was planned with the aim to study the two induced seismicity clusters and to collect a full-range of open-access data to be shared with the whole scientific community. The seismic network is composed by 8 stations deployed in an area of 17 km x 11 km around the two clusters of induced microearthquakes and it is equipped with triaxial weak-motion broadband sensors placed at different depths down to 50 m. It allows to detect induced microearthquakes, local/regional earthquakes, and teleseisms from continuous data streams transmitted in real-time to the CNR-IMAA Data Centre. The network has been registered at the International Federation of Digital Seismograph Networks (FDSN) with code 3F. Data collected until the end of the INSIEME project (2019-03-23) are already released with open-access policy through the FDSN webservices and are available from http://www.fdsn.org/networks/detail/3F_2016 (https://doi.org/10.7914/SN/3F_2016; Stabile et al., 2016).

A primary school in Rotonda was monitored during an on-going seismic sequence in the Pollino area, Southern Italy. The Reinforced Concrete (RC) building is a typical three story building with a concrete frame, bearing pre-cast slab flooring, concrete block internal walls and pre-cast external infill slabs. The monitoring began in September 2011 with a single station on top of the building, and after the M L = 5 mainshock occurred in October 2012 a network was completed with accelerometers on each floor and real-time streaming data was transmitted to the Istituto Nazionale di Oceanografia e Geofisica Sperimentale (Udine-Northern Italy). The school suffered no visible damage during the sequence. The real-time monitoring of the Rotonda school proved to be important for two reasons: (1) the large range of magnitudes and recorded peak accelerations allowed the study of the non-stationary frequency response; (2) the results also show how a simple, real-time monitoring system using cost-effective accelerometers could be used as a tool to provide information on the damage state and usability of the school.

After the ML = 6.0 earthquake which occurred on 24th August 2016 in central Italy, some unexpected variability in the damage distribution were identified in many villages located around the epicentral area. In particular, despite a distance of only about 1300 m, the villages of Pescara del Tronto and Vezzano (both districts in the Arquata del Tronto municipality) had a different damage assessment. Pescara del Tronto suffered heavy damage, with many collapsed masonry buildings and 48 fatalities, whereas Vezzano suffered negligible to slight damage to a few buildings. This paper provides vulnerability and damage assessment in order to detect potential significant differences in the building vulnerability and damage level. Geophysical prospectings were performed to assess whether site effects could have increased the damage in Pescara del Tronto compared to Vezzano.

Local earthquake tomography allows to both image the subsurface elastic properties of an area and to locate earthquakes. In this work, we discuss the choice of best parameterization in a tomographic model and the influence of retrieved velocity models on the accuracy of earthquake location in the High Agri Valley, southern Italy. The tomographic inversions were carried out with two datasets (dataset A and dataset B). Dataset B was obtained by integrating in the dataset A the data recorded by a very dense seismic network deployed around a specific cluster of seismicity. Velocity models obtained from the inversion of the two datasets are characterized by the same parameterization. However, the anomalies retrieved by the inversion of the second dataset look more reliable, based on results of checkerboard test. The retrieved 3D velocity model contributed to improve the accuracy of earthquake locations with respect to the 1D model. Data recorded by a very dense network in dataset B further contributed to reduce the errors and to improve the clustering of hypocentral positions of the best azimuthally covered cluster of seismicity. The importance of a 3D velocity model and of a proper network geometry for earthquake location is therefore demonstrated.

In this paper we present the result of a magnetotelluric (MT) investigation carried out across the High Agri Valley (HAV), southern Italy. Several MT soundings were carried out in order to obtain a ~15 km long 2-D resistivity model with an investigation depth of ~10 km. The main aim was to provide valuable data on the geological and structural setting of the HAV. The MT model was compared with pre-existing geological, geophysical and seismic data. The MT model can be schematized as a superposition of three stack lateral varying layers with different thickness and resistivity values: a surficial low–medium resistivity layer associated with the Quaternary deposits and to the allochthonous units; and a deeper high resistivity layer related to the Apulia Platform, separated by a thin layer connected to the mélange zone and to the Pliocene terrigenous marine deposits. Sharp lateral resistivity variations are interpreted as faults that, on the basis of accurate focal mechanism computations, display normal-faulting kinematics.

In this paper, we investigate the time dynamics of the seismicity of the area of the artificial Pertusillo Lake (southern Italy) by using two advanced statistical techniques: the robust periodogram and the singular spectrum analysis. Such methodologies are well suited to unveil the main characteristics (periodicities and long-term trend) of short time series, for which the application of standard statistical techniques fail. Our findings are that the monthly number of earthquakes occurred in the investigated area from 2002 to 2012 reveals the presence of the annual periodicity, which is reasonably linked with the yearly loading/unloading operational cycle of the lake. This indicates that the seismicity of the Pertusillo Lake area is effectively induced by the time-varying water level of the artificial lake. This result from one side sheds light on the nature of the earthquakes occurring in the investigated area as reservoir-induced, but, more generally, from another side suggests a robust manner to investigate the time dynamics of short seismic series. © 2014, Springer-Verlag Berlin Heidelberg.

On 2 June 2006 the wastewater produced during the oil and gas field exploitation in High Agri Valley (southern Italy) started to be managed by disposal through pumping the fluids back into the subsurface at the Costa Molina 2 (CM2) injection well, located in the southeastern sector of the valley. The onset of microearthquakes (Ml ≤ 2) after 4 days at about 1.3 km SW of CM2 well suggests fluid injection induced seismicity by the diffusion of pore pressure. Moreover, the space-time evolution of 196 high-resolution relocated events reveals a previously unmapped NE dipping fault. We investigate the physical processes related to the fluid injection induced seismicity and delineate the previously unmapped fault by jointly analyzing seismicity data, geological observations, fluid injection data, the stratigraphic log of the CM2 well, and the electrical resistivity tomography survey carried out in the study area.

This letter aims at analyzing the potentialities of the ground-based microwave radar interferometry technique for the dynamic characterization of civil infrastructures. This technique has been applied to estimate the fundamental dynamic parameters of the reinforced concrete Musmeci bridge in Basilicata region (southern Italy). The results have been validated by the comparison with the ones obtained applying consolidated techniques using data from accelerometers and tromometers. The good agreement obtained could suggest the joint application of such techniques as a new technological approach to set up a non-invasive and non-destructive evaluation procedure for structural health monitoring of infrastructures.

This paper aims at analysing the potentialities of a new technological approach for the dynamic monitoring of civil infrastructures. The proposed approach is based on the joint use of a high-frequency thermal camera and a microwave radar interferometer to measure the oscillations due to traffic excitations of the Sihlhochstrasse Bridge, Switzerland, which was selected as test bed site in the ISTIMES project (EU - Seventh Framework Programme). The good quality of the results encourages the use of the proposed approach for the static and dynamic investigation of structures and infrastructures. Moreover, the remote sensing character of the two applied techniques makes them particularly suitable to study structures located in areas affected by natural hazard phenomena, and also to monitor cultural heritage buildings for which some conventional techniques are considered invasive. Obviously, their reliability needs further experiments and comparisons with standard contact sensors.

The Campi Flegrei caldera (southern Italy) is one of the most hazardous areas in the world because it is home to several hundred thousand people live there and an important center of socio-economic activities. The caldera includes the western-most part of the city of Naples and extends into the Gulf of Pozzuoli (eastern Tyrrhenian basin; Figure 1). The main feature of the present volcanic activity of the caldera is the episodic slow and high-amplitude soil movement (bradyseism) accompanied by intense and shallow seismic activity that only occurs during the uplift phase. The most recent strong bradyseismic episode occurred between 1982 and 1984, when there was a maximum ground uplift of more than 170 cm, which was followed by slow and continuous subsidence, accompanied by rare low-amplitude uplifts (of a few centimeters). The maximum uplift was observed in the center of the caldera, in the town of Pozzuoli, while toward the caldera margins the uplift decreased gradually. The amplitude and the areal distribution of the vertical soil displacement that occurred over time in the marine sector, which covers more than one third of the caldera area, is completely unknown. During this 1982–84 bradyseismic episode, there were more than 10,000 shallow earthquakes (

In this paper the seismic behaviour of a Submerged Floating Tunnel (SFT) solution for the Messina Strait Crossing is investigated. The Submerged Floating Tunnel (SFT) is an innovative structural solution for the realization of waterway crossings, which features several advantages from the structural, economic and environmental impact points of view. In particular, it seems to be a suitable system for waterway crossings in high seismicity zones, thanks to the deformability of the overall structure. Moreover the interaction with the water provides additional damping and inertia to the structural motion. In order to evaluate the SFT structural response to seismic events, time domain dynamic analyses are carried out considering a ground multi-support excitation scenario determined through the generation of synthetic accelerograms by simulating the fault breaking mechanism. This is important due to the distance among the tunnel supports, also because it can lead to significant excitation of tunnel vibration modes featuring a negligible participating mass, which would not be excited in case of synchronous ground motion. Moreover the propagation of the vertical ground motion into the water and the fluid-structure interaction are taken into account in the analyses. Different structural solutions are considered, mainly differing for the cable system configuration. The dynamic properties of the considered solutions and the main aspects of their structural response are illustrated. The obtained results, although they cannot lead to definitive conclusions, give useful indications about the seismic response of Submerged Floating Tunnels and confirm that such an innovative structural solution for waterway crossings feature great potentialities, in particular when large spans have to be surpassed, such as in the Messina Strait crossing.

By using the global and local coefficient of variation and the Allan Factor we investigated the time-clustering properties of the time dynamics of fluid-injection–induced microseismicity. The experiment consists of a microseismic monitoring through a nearly vertical borehole of 12 receivers of a hydraulic fracturing stimulation along a horizontal well separated into more than 20 sections (stages) The main finding of the applied methodology is the discrimination between fault triggering and new fracturing, being the first characterized by a clusterization of the induced microseismic events and the second by a Poissonian behaviour of the generated events.

A non-linear, global-search, probabilistic, double-difference earthquake location technique is illustrated. The main advantages of this method are the determination of comprehensive and complete solutions through the probability density function (PDF), the use of differential arrival times as data and the possibility to use a 3-D velocity model both for absolute and double-difference locations, all of which help to obtain accurate differential locations in structurally complex geological media. The joint use of this methodology and an accurate differential time data set allowed us to carry out a high-resolution, earthquake location analysis, which helps to characterize the active fault geometries in the studied region. We investigated the recent microseismicity occurring at the Campanian-Lucanian Apennines in the crustal volume embedding the fault system that generated the 1980 M-S 6.9 earthquake in Irpinia. In order to obtain highly accurate seismicity locations, we applied the method to the P and S arrival time data set from 1312 events (M-L < 3.1) that occurred from August 2005 to April 2011 and used the 3-D P- and S-wave velocity models optimized for the area under study. Both manually refined and cross-correlation refined absolute arrival times have been used. The refined seismicity locations show that the events occur in a volume delimited by the faults activated during the 1980 MS 6.9 Irpinia earthquake on subparallel, predominantly normal faults. We find an abrupt interruption of the seismicity across an SW-NE oriented structural discontinuity corresponding to a contact zone between different rheology rock formations (carbonate platform and basin residuals). This 'barrier' appears to be located in the area bounded by the fault segments activated during the first (0 s) and the second (18 s) rupture episodes of the 1980s Irpinia earthquake. We hypothesize that this geometrical barrier could have played a key role during the 1980 Irpinia event, and possibly controlled the delayed times of activation of the two rupture segments.