Venuti, Alessandra

We provide a database of the surface ruptures produced by the 26 December 2018 Mw 4.9 earthquake that struck the eastern flank of Mt. Etna volcano in Sicily (southern Italy). Despite its relatively small magnitude, this shallow earthquake caused about 8 km of surface faulting, along the trace of the NNW-trending active Fiandaca Fault. Detailed field surveys have been performed in the epicentral area to map the ruptures and to characterize their kinematics. The surface ruptures show a dominant right-oblique sense of displacement with an average slip of about 0.09 m and a maximum value of 0.35 m. We have parsed and organized all observations in a concise database, with 932 homogeneous georeferenced records. The Fiandaca Fault is part of the complex active Timpe faults system affecting the eastern flank of Etna, and its seismic history indicates a prominent surface-faulting potential. Therefore, this database is essential for unravelling the seismotectonics of shallow earthquakes in volcanic areas, and contributes updating empirical scaling regressions that relate magnitude and extent of surface faulting.

We present the results of a combined analysis of remote sensing and geophysical ‐ geotechnical data carried out in the Acque Albule Basin, a sinkhole prone area located close to the city of Roma, where a wide travertine wedge is present. We carried out geophysical measurements and borehole drillings over two test areas to image the subsoil where paroxysmal sur fi cial dynamics occur. One site is marked by subsidence occurring at least since the early 2000s, whereas the other site hosts the “ La Regina ” and “ Colonnelle ” sinkhole lakes, which discharge sulfur ‐ carbonated waters. The stability of these two sites threatens highway, railway, and airport facilities, and this study helps to assess the geological hazard. For example, InSAR and LiDAR data helped de fi ne wide scale subsidence over the last 20 years and previously undetected small ‐ scale morphologies. Geophysical measurements of the latter revealed shallow and deep dissolution affecting the travertine and driving sur fi cial paroxysmal events. Both study sites were found to lie inside a large depression located at the junction between Jurassic carbonate and Plio ‐ Pleistocene units in association with paleo karst morphologies in the travertine deposits and affected by the present ‐ past spillage of sulfurous waters. Given these elements, multidisciplinary geophysical observations are crucial for assessing and mitigating the geological risk and guiding land use planning and management.

Il terremoto del 26 dicembre 2019, ore 02:19 UTC, che ha colpito il basso versante sud-orientale dell’Etna, ha prodotto non solo danni gravi e distruzioni nell’area epicentrale, pari al grado 8 EMS (Azzaro et al., in questo volume), ma anche vistose rotture superficiali lungo la faglia di Fiandaca, che è la struttura più meridionale del sistema tettonico delle Timpe (Fig. 1a). Gli effetti di fagliazione cosismica in area etnea sono storicamente piuttosto frequenti in occasione di terremoti superficiali (< 2-3 km), anche per valori di magnitudo relativamente modesti (M ≥ 3.5, vedi Azzaro, 1999). Con una magnitudo Mw 4.9 (Regional Centroid Moment Tensors, https://doi.org/10.13127/rcmt/italy), il terremoto in questione rappresenta l’evento più significativo, in termini di entità e complessità della fagliazione associata, verificatosi nell’area etnea negli ultimi 70 anni, con una estensione della rottura superiore rispetto a quelle storiche (< 6.5 km). Il gruppo di emergenza per il rilievo degli effetti geologici cosismici EMERGEO (http://emergeo.ingv.it) dell’INGV, si è pertanto attivato effettuando quattro campagne di misura con squadre che si sono alternate sul terreno (per un totale di 60 gg/persona), supportate da personale del proprio Centro Operativo per l’organizzazione dei dati e il popolamento del database (43 gg/persona). Il rilievo ha consentito la raccolta e catalogazione di circa 900 punti di misura relativi a posizionamento, geometria, rigetto e cinematica delle fratture cosismiche.

We present a 1:10,000 scale map of the coseismic surface ruptures following the 26 December 2018 Mw 4.9 earthquake that struck the eastern flank of Mt. Etna volcano (southern Italy). Detailed rupture mapping is based on extensive field surveys in the epicentral region. Despite the small size of the event, we were able to document surface faulting for about 8 km along the trace of the NNW-trending active Fiandaca Fault, belonging to the Timpe tectonic system in the eastern flank of the volcano. The mapped ruptures are characterized in most cases by perceivable opening and by a dominant right-oblique sense of slip, with an average slip of about 0.09 m and a peak value of 0.35 m. It is also noteworthy that the ruptures vary significantly in their kinematic expression, denoting locally high degree of complexity of the surface faulting.

We provide a database of the coseismic geological surface effects following the Mw 6.5 Norcia earthquake that hit central Italy on 30 October 2016. This was one of the strongest seismic events to occur in Europe in the past thirty years, causing complex surface ruptures over an area of >400 km2. The database originated from the collaboration of several European teams (Open EMERGEO Working Group; about 130 researchers) coordinated by the Istituto Nazionale di Geofisica e Vulcanologia. The observations were collected by performing detailed field surveys in the epicentral region in order to describe the geometry and kinematics of surface faulting, and subsequently of landslides and other secondary coseismic effects. The resulting database consists of homogeneous georeferenced records identifying 7323 observation points, each of which contains 18 numeric and string fields of relevant information. This database will impact future earthquake studies focused on modelling of the seismic processes in active extensional settings, updating probabilistic estimates of slip distribution, and assessing the hazard of surface faulting.

We present a 1:25,000 scale map of the coseismic surface ruptures following the 30 October 2016 M-w 6.5 Norcia normal-faulting earthquake, central Italy. Detailed rupture mapping is based on almost 11,000 oblique photographs taken from helicopter flights, that has been verified and integrated with field data (>7000 measurements). Thanks to the common efforts of the Open EMERGEO Working Group (130 people, 25 research institutions and universities from Europe), we were able to document a complex surface faulting pattern with a dominant strike of N135 degrees-160 degrees (SW-dipping) and a subordinate strike of N320 degrees-345 degrees (NE-dipping) along about 28km of the active Mt. Vettore-Mt. Bove fault system. Geometric and kinematic characteristics of the rupture were observed and recorded along closely spaced, parallel or subparallel, overlapping or step-like synthetic and antithetic fault splays of the activated fault systems, comprising a total surface rupture length of approximately 46km when all ruptures were considered.

We present the results of multidisciplinary investigations of two significant sites, located in the Acque Albule Basin (AAB), 25 km Northeast of Rome (Italy). This basin has been interpreted as a transtensional structure, lying in the western margin of the Apennine range and affecting the Plio-Pleistocene sedimentary and volcanic sequences. During late Pleistocene times, AAB has been filled in with thermogenic travertine of variable thickness. Since historical time, lithoid travertine has been quarried, becoming the main building material during the Roman period (Lapis Tiburtinus). At present, the mining activity still represents the main economic resource of the region together with thermal baths. After the end of the II World War this area has experienced a strong urbanization and marshy lands were transformed into densely populated areas affected by subsidence and sinkhole phenomena. In order to characterize these environmental hazards from the geophysical and geotechnical point of view, we chose two test sites close to relevant anthropic infrastructures. Site A, located at the southern side of the Guidonia military airport and beside an important road; site B, a few kilometers South-East of site A, lies next to the Regina and Colonnelle Lakes and close to the Roma- Pescara railway. The former feature is a large sinkhole depression, hundreds of meters in width, characterized by ongoing subsidence, whereas the latter consists of two sinkholes actually acting as springs. Both sites lie in proximity of inferred faults, which would affect the AAB in the N-S and NE-SW– directions respectively. The aim of this study is to compare the two cases by collecting geological, geomorphological and geophysical parameters and thus testing the variable controlling their formation and development. We also extended the geophysical campaign in the surrounding area using a multidisciplinary approach to image both surface and subsurface features. We carried out stratigraphic and geomorphological survey, 2 and 3D Geoelectrical Tomography (ERT), differential GPS altimetry, gravity, magnetic, seismic, and soil gas measurements. Moreover, two drillings have been bored inside and outside the depression area of the Site A, reaching depths of 60 and 20 meter, respectively. Geotechnical parameters of the recovered stratigraphy were also measured by laboratory tests. In general, the approach we propose could provide key elements to recognize similar situations in sinkhole prone areas. Moreover, comparative analysis together with the monitoring of the A site can represent useful tools to understand the genesis and dynamics of phenomena and hopefully to forecast their evolution, particularly in the parts of the basin where active movements caused fractures and damages to buildings and infrastructures.

Magnetic susceptibility (MS) is employed among others magnetic pa- rameters to investigate pollution along a high traffic density road. In this study, MS field survey and magnetic laboratory analyses were applied to five sites along the Via Salaria road in the northern districts of Rome. Scanning electron microscope and energy dispersive spectroscopy analy- ses have also been employed to reveal the nature of Fe rich particles of an- thropogenic origin. In general, the soil samples revealed to contain low coercivity minerals (e.g., magnetite) with different grain size, Fe-oxides occurring in various forms (spherules, aggregates, octahedral crystals and angular particles) are typically found close to the road side border at some of the analyzed sites. Magnetic minerals concentration in proximity of the road border resulted higher at sites with higher traffic volume and, in general, decreases with the distance from it. Evidences of anthropogenic material in topsoils were found within the first 5 m from the road border. The study confirms that the in situ measurements of the magnetic sus- ceptibility are a valuable tool to rapidly investigate variations in the mag- netic susceptibility profile related to anthropogenic contribution.

The Plio-Quaternary Acque Albule Basin is already known for the occurrence of sinkholes; since the spring 2014, it has been ongoing the study of an active subsidence process, which formed a depressed area near the Guidonia village. During the last year, the phenomenon has become more intense giving rise to two collapses along the eastern rim of the depression. Thus, geophysical and geogeochemical investigation campaigns started in order to understand the genesis and evolution of the phenomenon. Survey results allowed a geological and structural characterization, showing the presence of “travertino” at the depression margins and its absence therein. It has been recognized, by the geophysics, features with NW-SE and NNE-SSW direction ascribable to a possible depression fracturing and consistent with regional structural trends. Thus, it has been possible to plan and perform geognostic investigation consisting in two drillings aimed to define the stratigraphy of the marginal and inner part of the depression.

Sinkhole occurrence along the Tyrrhenian margin of the Central Apennines is of great importance for applied research, land management and civil protection. This study reports on GPS-altimetry magnetic, gravity, geoelectric, seismic, and soil gas measurements of a rapidly developing sinkhole near the Guidonia military airport. The measurements revealed an elliptical 2-m depression elongated 220 m in the NNE-SSW direction with the minor axis of 110 m. In spring of 2013, two vertical cavities formed in the eastern and northeastern flanks of the depression whose depths and shapes are rapidly evolving with the formation of widespread fracturing along the same side. The geophysical observations image the developing sinkhole to a depth of some 50 m, the presence of the Travertino lithotype around the depression (down to at least 40 m), and the lack of this lithotype below the lowered area. The sinkhole's evolution appears to be structurally controlled by local and regional faulting. These results are useful for designing further geophysical, geotechnical and geochemical studies to monitor the sinkhole's evolution and to assess the hazard it presents in densely urbanized area.