Galvani, Alessandro

An accurate survey of old and new datasets allowed us to probe the nature and role of fluids in the seismogenic processes of the Apennines mountain range in Italy. New datasets include the 1985–2021 instrumented seismicity catalog, the computed seismogenic thickness, and geodetic velocities and strains, whereas data from the literature comprise focal mechanism solutions, CO2 release, Moho depth, tomographic seismic velocities, heat flow and Bouguer gravity anomalies. Most of the inspected datasets highlight differences between the western and eastern domains of the Apennines, while the transition zone is marked by high geodetic strain, prevailing uplift at the surface and high seismic release, and spatially corresponds with the overlapping Tyrrhenian and Adriatic Mohos. Published tomographic models suggest the presence of a large hot asthenospheric mantle wedge which intrudes beneath the western side of the Apennines and disappears at the southern tip of the southern Apennines. This wedge modulates the thermal structure and rheology of the overlying crust as well as the melting of carbonate-rich sediments of the subducting Adriatic lithosphere. As a result, CO2-rich fluids of mantle-origin have been recognized in association with the occurrence of destructive seismic sequences in the Apennines. The stretched western domain of the Apennines is characterized by a broad pattern of emissions from CO2-rich fluids that vanishes beneath the axial belt of the chain, where fluids are instead trapped within crustal overpressurized reservoirs, favoring their involvement in the evolution of destructive seismic sequences in that region. In the Apennines, areas with high mantle He are associated with different degrees of metasomatism of the mantle wedge from north to south. Beneath the chain, the thickness and permeability of the crust control the formation of overpressurized fluid zones at depth and the seismicity is favored by extensional faults that act as high permeability pathways. This multidisciplinary study aims to contribute to our understanding of the fluid-related mechanisms of earthquake preparation, nucleation and evolution encouraging a multiparametric monitoring system of different geophysical and geochemical observables that could lead the creation of a data-constrained and reliable conceptual model of the role of fluids in the preparatory phase of earthquakes in the Apennines.

The identification of the mechanisms responsible for the deformation of calderas is of primary importance for our understanding of the dynamics of magmatic systems and the evaluation of volcanic hazards. We analyze twenty years (1997–2018) of geodetic measurements on Ischia Island (Italy), which include the Mt. Epomeo resurgent block, and is affected by hydrothermal manifestations and shallow seismicity. The data from the GPS Network and the leveling route show a constant subsidence with values up to 􀀀15 2.0 mm/yr and a centripetal displacement rate with the largest deformations on the southern flank of Mt. Epomeo. The joint inversion of GPS and levelling data is consistent with a 4 km deep source deflating by degassing and magma cooling below the southern flank of Mt. Epomeo. The depth of the source is supported by independent geophysical data. The Ischia deformation field is not related to the instability of the resurgent block or extensive gravity or tectonic processes. The seismicity reflects the dynamics of the shallow hydrothermal system being neither temporally nor spatially related to the deflation.

We investigated the interseismic GPS velocity field across the transition zone between Central and Southern Apennine comprising the Meta–Mainarde-Venafro and Alto Molise–Sannio-Matese mounts. The kinematic field obtained by combining GPS network solutions is based on data collected by the unpublished episodic campaigns carried out on Southern Apennine Geodetic network (SAGNet from 2000 to 2013), IGM95 network (Giuliani et al., 2009 from 1994 to 2007) and continuous GPS stations. The data collected after the 29 December 2013 earthquake (Mw 5.0) until early 2014 allowed estimating displacements at 15 SAGNet stations. The extension rate computed across the Matese massif along an anti-Apennine profile is 2.0±0.2 mm/yr. The interseismic velocities projected along the profile show that the maximum extension does not follow the topographic high of the Apennines but is shifted toward the eastern outer belt. No significant GPS deformation corresponding to inner faults systems of the Matese massif is detected. Taking into account our results and other geophysical data, we propose a conceptual model, which identifies the 2013–2014 seismic sequence as not due to an extensional deformation style usual along the Apennine chain. In fact, we have measured too large “coseismic” displacements, that could be explained as the result of tectonic regional stress, CO2-rich fluid migration and elastic loading of water in the karst Matese massif. We recognized a tensile source as model of dislocation of 2013–2014 earthquakes. It represents a simplification of a main fault system and fracture zone affecting the Matese massif. The dislocation along NE-dipping North Matese Fault System (NMFS) could be the driving mechanism of the recent seismic sequences. Moreover, to the first time the SAGnet GPS data collected from 1994 to 2014, are share and available to the scientific community in the open access data archive.

We investigated whether the joint inversion of geodetic and stress direction data can constrain long‐term fault slip rates in the central Apennines, and ultimately how extension is partitioned among fault slip and bulk lithosphere permanent strain. Geodetic velocities are collected in the fault interseismic stage with steady secular deformation; thus, long‐term estimates can be derived with a model of elastically unloading seismogenic faults within a viscously deforming lithosphere. As the average spacing of permanent Global Navigation Satellite Systems (GNSS) stations is similar to the average length of seismogenic faults (25–35 km), if not larger, we decided to merge permanent and temporary GNSS measurements, resulting in a denser geodetic data set. Given that most normal faults in the Apennines have slip rates around or below 1 mm/a, and most campaign GNSS velocities carry similar uncertainties, simple local back slip models cannot be applied. More sophisticated modeling is required to extract reasonable bulk deformation rates and long‐term fault slip rates at signal‐to‐noise ratio of order unity. Given the spatial distribution of the GNSS network, we estimated the long‐term slip rate of seven major fault systems that are in satisfactory agreement with available geological slip rates. The resulting spatial distribution of bulk deformation rates locally fits short‐term transients; in other cases, they represent the currently unclear signature of tectonic processes like upper‐crustal viscoplastic deformation and aseismic slip, or indicate missing faults in the adopted database. We conclude that the time is ripe for determining fault slip rates using geodetic and stress direction data, particularly where fault activity rates are hard to determine geologically.

The Sorrentina Peninsula is a densely populatedarea with high touristic impact. It is located in a morphologically complex zone of Southern Italy frequently affected by dangerous and calamitous landslides. This work contributes tothe prevention of such natural disasters by applying a GIS-based interdisciplinary approach aimed to map the areas more potentially prone to trigger slope instability phenomena. We have developed the Landslide Susceptibility Index (LSI) combining five weighted and ranked susceptibility parameters on a GIS platform. These parameters are recognized in the literature as the main predisposing factors for triggering landslides. This work combines analyses conducted on Remote Sensing, Geo-Lithology and Morphometry data and it is organized in the following logical steps: i) Multi-temporal InSAR technique was applied to Envisat-ASAR (2003–2010) and COSMO-SkyMed (2013–2015) datasets to obtain the ground displacement time series and the relative mean ground velocity maps. InSAR allowed the detection of the areas that are subjected to ground deformation and the main affected municipalities;ii) Such deformation areas were investigated through airborne photointerpretation to identify the presence of geomorphological peculiarities connected to potential slope instability. Subsequently, some of these peculiarities were checked on the field; iii) In these deformation areas the susceptibility parameters were mapped in the entire territory of Amalfi and Conca dei Marini and then investigated with a multivariate analysisto derive the classes and the respective weights used in the LSI calculation. The resultingLSI map classifies the two municipalities with high spatial resolution (2m) according to five classes of instability. The map highlights that the high/very high susceptibility zones cover6% of the investigated territory and correspond to potential landslide source areas characterized by 25°-70° slope angles. A spatial analysis between the map of the historical landslides and the areas classifiedaccording to susceptibility allowed testing of the reliability of the LSI Index, resulting in 85% prediction accuracy.

Deep Seated Gravitational Slope Deformations are characterized by low deformation rates although they can experience partial-collapse phases or more rapid movements, especially in presence of active tectonic structures. In the Central Italy, considering the high seismicity rate, seismic activity must be considered to be an important trigger of deep slope movements. We aim to contribute to the research in this field by reporting the results of a monitoring program on a Deep Seated Gravitational Slope Deformation in this region that involves marly calcareous rocks. We documented the pre-earthquakes evolution of the phenomenon and measured its displacements during the seismic sequence in 2016 and 2017 in Central Italy, which largest events were Mw 5.0-to-6.5. A multidisciplinary approach that combines a field geomorphological survey, installation of permanent GPS stations, and InSAR elaborations was adopted for this study. The average ground motion rate of the slope deformation before the earthquakes was very low (< 3 mm/y) and not spatially homogenous, as detected by GPS and InSAR. In detail, the uppermost area of the slope instability likely moves faster than the lowest sector. On the other hand, GPS and InSAR recorded significant step-like movements, one to ten times higher than the normal activity rate, triggered by the M-w 5.0-to-6.5 earthquakes. In detail, the movement mainly depended on the magnitude of the earthquake and the distance from the epicenter, and only secondarily on the number of larger magnitude earthquakes on a given day. In conclusion, we furnished monitoring data on the activity rate of a Deep Seated Gravitational Slope Deformation in seismic context, we indicated two sectors of the investigated deformation that resulted more unstable and we proved that the combination of InSAR and GPS data is a useful monitoring system for earthquake activated, slow-moving slope instabilities.

We investigate a large geodetic data set of interferometric synthetic aperture radar (InSAR) and GPS measurements to determine the source parameters for the three main shocks of the 2016 Central Italy earthquake sequence on 24 August and 26 and 30 October (Mw 6.1, 5.9, and 6.5,respectively). Our preferred model is consistent with the activation of four main coseismic asperities belonging to the SW dipping normal fault system associated with the Mount Gorzano-Mount Vettore-Mount Bove alignment. Additional slip, equivalent to aMw~ 6.1–6.2 earthquake, on a secondary (1) NE dipping antithetic fault and/or (2) on a WNW dipping low-angle fault in the hanging wall of the main system is required to better reproduce the complex deformation pattern associated with the greatest seismic event (the Mw 6.5 earthquake). The recognition of ancillary faults involved in the sequence suggests a complex interaction in the activated crustal volume between the main normal faults and the secondary structures and a partitioning of strain release.

We present a full 3-D velocity field of the Earth’s surface in the Euro-Mediter ranean area obtained from a combination of three different velocity solutions computed at the Centro Nazionale Terremoti (CNT) of the Istituto Nazionale di Geofisica e Vulcanologia (INGV). All the publicly available GPS data since 1993, have been fully reprocessed by three different software tools and the final velocity field is estimated combining three independent velocity solutions in a least squares sense. The input velocity solutions are treated as stochastic sam- ples of the true velocity field by loosening the reference frame constraints in the associated variance-covariance matrix. The proposed approach allows for a fast and efficient combination of multi velocity solutions, taking into account the full network covariance, if available. The velocity map for the Euro-Medi- terranean region will be updated and released regularly on the web portal of the National GPS Network (http://ring.gm.ingv.it) and made available to the scientific community. Here we show and discuss the data analysis and the combination schemes, and the results of the combined velocity field.

The GPS results are of utmost relevance for the study of the complex plate boundary geodynamics. The lithosphere strain partitioning is part of the seismic cycle. We present the first GPS kinematic pattern obtained during the interseismic phase by a dense episodic GPS network, the Southern Apennine Geodetic Network - SAGNet (Sepe et al., 2009), in the time span 2002-2013. This network is located across the transition zone between central and southern Apennine, including Meta-Mainarde-Venafro and AltoMolise-Sannio-Matese mounts. This region is characterized by seismogenic fault systems responsible, in the past, for several destructive earthquakes of intensity I ≥ IX MCS and, in more recent years, characterised mainly by some moderate magnitude seismic sequences (max magnitude Mw 5.0, December 29 2013) and single small events (Ml < 2.5).SAGNet GPS data were processed by BERNESE sw v.5.0 and the resulting velocities were least-squares combined with the permanent stations velocity field and with the velocity solution of Giuliani et al. 2009. The combined GPS velocity field, shows a perpendicular maximum extension with respect to the Apennine chain of about 2.0 mm/y.The Matese area was hit on December 29, 2013 by a Mw=5.0 (Convertito et al., 2016) earthquake. It was followed by an intense seismic activity until the beginning of February 2014. After the mainshock a GPS survey was carried out on the SAGnet stations. We collected data from 2013, 30 December to 2014, 4 April. The time series of 17 stations are affect by an offsets on the linear drift. The map of horizontal coseismic displacements (Figure 3) shows a sub-radial displacement shape with respect to the epicentre. Larger displacements are observed in correspondence of NE portion of the Matese massif. Considering the Matese Lake Fault as the probable source of the mainshock (dip 65°, strike 116, rake 270 – MLF, Ferranti et al, 2015), we found that the Okada modelling does not fit the observed displacements and only a small fraction of displacements are resolved with a simple slip.Figure 4 resembles the results of previous studies compared with our GPS analysis. We considered seismological analyses, tomographic models, degassing of CO2 data and conceptual model of processes recognized in South Apennine (L. Bisio, et al., 2004; Chiarabba and Chiodini, 2013; Improta et al., 2014; Ventura et al., 2007, R. Di Stefano and M.G. Ciaccio, 2014; Ferranti et al., 2015; Convertito et al., 2016;). The GPS results indicate that the relative motion between Eurasia and Adria plates is responsible of the active deformation in the Apennines. The most important outcomes of this study are: (i) During the interseismic phase the differential motion between Adriatic and Tyrrhenian domains seems to be accommodated in a narrow belt bordering the westward flank of the Sannio Mts, showing a 2 mm/y extension. (ii) The maximum extension does not follow the topographic high of the chain but is shifted toward the eastern outer belt. (iii) No significant GPS deformation is highlighted in correspondence of major and known fault systems where the GPS velocities appear almost steady. We propose that the observed coseismic displacements are only marginally explained by a slip on the MLF fault. The vertical directivity and depth distribution of the seismic sequence (Convertito et al., 2016), the vertical and horizontal heterogeneity of lower crust and upper mantle (Bisio et al., 2004; Di Stefano and Ciaccio, 2014), the high flux of CO2 degassing (Ventura et al., 2007, Chiarabba e Chiodini, 2013 ), the probable presence of pressurized CO2 bodies fed by fluids uprising from the mantle wedge (Improta et al.,2014 ), suggest instead that the seismic sequence could be caused by sub-vertical cracks that originate at the Moho interface and reach the bottom of the seismogenic layer (10km depth).

We used continuous Global Positioning System (GPS) measurements to infer the fault geometry and the amount of coseismic slip associated to the August 24, 2016 Mw 6 Amatrice earthquake. We realized a three-dimensional coseismic displacement field by combining different geodetic solutions generated by three independent analyses of the raw GPS observations. The coseismic deformation field described in this work aims at representing a “consensus” solution that minimizes the systematic biases potentially present in the individual geodetic solutions. Because of the limited number of stations available we modeled the measured coseismic displacements using a uniform slip model, deriving the geometry and kinematics of the causative fault, finding good agreement between our geodetically derived fault plane and other seismological and geological observations.