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Abstract: We investigate the L'Aquila 2009 earthquake (AQE, Mw 6.3, Italy) through a 3‐D Finite Element (FE) mechanical model based on the exploitation of ENVISAT DInSAR and GPS measurements and an independently generated fault model. The proposed approach mainly consists of (a) the generation of a 3‐D fault model of the active structures involved in the sequence and those neighboring to them, benefiting of a large geological and seismological data set; (b) the implementation of the generated 3‐D fault model in a FE environment, by exploiting the elastic dislocation theory and considering the curved fault geometry and the crustal heterogeneities information; and (c) the optimization of the seismogenic crustal blocks model parameters in order to reproduce the geodetic measurements. We show that our modeling approach allows us to well reproduce the coseismic surface displacements, including their significant asymmetric pattern, as shown by the very good fit between the modeled ground deformations and the geodetic measurements. Moreover, a comparative analysis between our FE model results and those obtained by considering a classical analytical (Okada) model, for both the surface displacements and the Coulomb stress changes, has been performed. Our model permits to investigate the coseismic stress and strain field changes relevant to the investigated volume and their relationships with the surrounding geological structures; moreover, it highlights the very good correlation with the seismicity spatial distribution. The retrieved stress field changes show different maxima: (a) at few kilometers depth, within the main event surface rupture zone; (b) at depths of 5–9 km in correspondence of main event hypocentral area, along the SW dipping Paganica Fault System (PFS); and (c) at depths of 12–14 km, in correspondence of the largest aftershock hypocentral area, along a steep segment of an underlying east dipping basal detachment. Moreover, the main event hypocenter is localized in a region of high‐gradient strain field changes, while a deeper volumetric dilatation lobe involves the largest aftershock zone. From these findings, we argue that the AQE hanging wall downward movement along the steep portion of PFS might have been modulated by the underlying basal detachment; on the other hand, the coseismic eastward motion of the PFS footwall might have triggered further slip on the OS, thus releasing the largest aftershock on an independent source. The retrieved stress and strain field changes, which support the active role of the OS, have been also validated through a comparative analysis with those obtained from independent geological, seismological, and GPS measurements. [ABSTRACT FROM AUTHOR]

We present the results of an interdisciplinary study aimed at defining the geometry of the fault segments activated by the Emilia 2012 thrust sequence (MW up to 6.1), which are located at the front of the Ferrara Arc (northern Italy) and partially overlap with an area undergoing hydrocarbon exploitation since 1980 (Cavone oil field). We relocate 40 well-recorded earthquakes with MW prevailingly ≥4.0 in the time interval from May 20 to June 12, 2012, plus an event that occurred in a nearby area on July 17, 2011 (MW 5.0). The geological and seismotectonic setting of the area is discussed, some interpretative geological sections across the hypocentral volumes are elaborated, and the shape of the identified individual seismogenic fault segments is schematically represented as depth contour lines. The resulting earthquake/fault association highlights a rather complex segmentation pattern, with four neighbouring sources involved, all belonging to the SSW-dipping Ferrara Thrust System. The two main events of the Emilia 2012 sequence did not activate the Mirandola thrust underlying the Cavone reservoir, although this thrust was illuminated by some subsidiary activity mainly concentrated close to the hydrocarbon field. The likelihood of triggered seismicity effects due to the extraction/ injection activities within the Cavone oil field are discussed. [ABSTRACT FROM AUTHOR]

The seismogenic potential of active faults in the Abruzzo region of central Italy has been tragically brought to the general attention by the April 6, 2009 L'Aquila earthquake. In this region, a system of SW-dipping normal faults has been active both in historical and recent times, with at least three moderate-to-large earthquakes (Avezzano 1915, Barrea 1984, and L'Aquila 2009) and several minor seismic sequences. Some highly populated areas, like the Sulmona basin at the hanging wall of the Mt. Morrone fault (a segment capable of releasing destructive earthquakes, Mmax~6.7), have not experienced significant earthquakes in the last millennium; the time lapse since the last event should therefore be comparable with the recurrence time assigned to this fault, enhancing its contribution to seismic hazard in a time-dependent perspective. With the aim of increasing our knowledge on the active deformation pattern, geometry and seismogenic depth of the potential structures by means of low-magnitude seismicity, a bulk of temporary seismometric stations has been installed in the Sulmona area. The small network is managed by OGS (Istituto Nazionale di Oceanografia e Geofisica Sperimentale) and GeosisLab (Chieti-Pescara University) and it consists of six mobile stations set in continuous recording mode and local data storage. The data processing consists in the recognition on the continuous recordings of local events, undetected by the permanent Italian seismic network managed by INGV (Istituto Nazionale di Geofisica e Vulcanologia), and in the location of these small events. Event identification during an ongoing seismic sequence (in our case the 2009 L'Aquila one) is not easy; when the processing of manual pickings is completed, we expect the temporary seismic network to lower the magnitude of completeness in the Sulmona area by about 1 degree, to M<1 events, with significant advantages for studies with seismotectonic and seismic hazard purposes. Some preliminary results on the quality of the seismic recorded data from May 27 to July 15, 2009 and on their spatial distribution are presented. [ABSTRACT FROM AUTHOR]

Many joint inversion schemes use 1D forward modelling in the integrated interpretation of various geophysical data. In extending the joint inversion approach to the investigation of 2D structures, the discretization of the model parameters and the appropriate choice of the forward-modelling procedure play a very important role. In this paper, a hybrid seismic–geoelectric joint inversion method is proposed for the investigation of 2D near-surface geological structures. The electric and seismic models are coupled together through the use of common boundaries between the adjacent layers. Assuming a 2D model composed of homogeneous layers with curved boundaries, a fast ray-tracing algorithm is used for the calculation of refraction seismic traveltime data. In the geoelectric forward modelling, a locally 1D approximation is used. The boundary surfaces are written in the form of series expansion; the inversion algorithms are formulated for the expansion coefficients and the petrophysical parameters as unknowns. Two versions of the inversion method are proposed: in versions A and B, interval-wise constant functions and Chebyshev polynomials are, respectively, used as basis functions of the series expansion. The versions are tested by means of synthetic and in situ measured data. The tests show that both methods are stable and accurate. [ABSTRACT FROM AUTHOR]

Despite the high detection level of the Italian seismic network and the risk associated with its fault networks, Central‐Southern Italy has no unique geophysical model of the crust able to illuminate its complex tectonics. Here, we obtain seismic attenuation and scattering tomography models of this area; both reveal high attenuation and scattering anomalies characterizing the entire Apenninic Chain and related to its East‐ and West‐dipping extensional Quaternary tectonic alignments. Fault‐associated fractured zones become preferential ways for circulating and degassing high‐attenuation CO2‐bearing fluids. A previously undetected fluid source area is a high‐attenuation volume below the Matese complex, while a similar smaller anomaly supports a fluid source near L'Aquila. The most prominent low attenuation and scattering volumes reveal a locked aseismic zone corresponding to the Fucino‐Morrone‐Porrara fault systems, representing a zone of significant seismic hazard. Plain Language Summary: Geophysical methods are the most used tools for imaging the subsurface. Still, their resolution and reliability depend on the amount of good‐quality data and the sensitivity of the technique used for the target structures. Improvements in the seismic detection infrastructures of the last decade allow imaging zones characterized by sparse seismicity, like Central‐Southern Italy. Once combined with these data, new imaging techniques targeting attributes with higher sensitivity to stress and fluid saturation provide unprecedented resolution on tectonic interactions and fluid sources in this area. Here, we measured and mapped in 3D the energy lost by seismic waves during their propagation. Our results show a high‐attenuation volume elongated in the direction of the Apenninic Chain and particularly intense in Southern Italy, mapping fluid‐filled fracturing and a fluid source likely coinciding with the Matese area. The principal normal and reverse faults in the area control high‐attenuation zones. The most prominent low attenuation and scattering volume marked locked areas with low seismic energy release, suggesting them as the zones of stress accumulation. Key Points: Scattering and attenuation tomography image the tectonics of the Apennine Mountain Belt ChainHigh‐attenuation anomalies mark crustal sources of CO2 following major structural alignmentsA high‐attenuation/high‐scattering volume reveals an extended fluid source beneath the Matese Mountains [ABSTRACT FROM AUTHOR]

Abstract: A quantitative prediction of seismic site effects requires the definition of a subsoil parametric model for ground motion numerical modelling. This paper describes an application of integrated geophysical methods to define an earthquake engineering parametric model for the seismic zonation of the municipal area of Celano, Italy. In municipal areas of such extent, particularly in case of complex geology, subsurface characterization is an optimization procedure, where the objective function to be minimized is the uncertainty related to the subsoil features, under the constraint of fixed resources and logistical limitations. In the particular case of Celano, correlation between different geophysical results was very profitable in discriminating different geological scenarios in the historical centre and in areas designed for urban expansion, while defining the elastic properties of the near-surface deposits throughout the municipal area. [Copyright &y& Elsevier]

The integrated interpretation of high-resolution multibeam bathymetry, seismic profiles and backscatter data in the S. Eufemia Gulf (SEG; Calabro-Tyrrhenian continental margin, south-eastern Tyrrhenian Sea) documents the relationship between postglacial fault activity and morpho-sedimentary processes. Three systems of active normal faults that affect the seafloor or the shallow subsurface, have been identified: 1) the S. Eufemia fault system located on the continental shelf with fault planes mainly oriented N26E-N40E; 2) the offshore fault system that lies on the continental slope off Capo Suvero with fault planes mainly oriented N28E-N60E; 3) the Angitola Canyon fault system located on the seafloor adjacent to the canyon having fault planes oriented N60E-N85E. The faults produce a belt of linear escarpments with vertical displacement varying from a few decimeters to about 12 m. One of the most prominent active structures is the fault F1 with the highest fault length (about 9.5 km). Two main segments of this fault are identified: a segment characterised by seafloor deformation with metric slip affecting Holocene deposits; a segment characterised by folding of the seafloor. A combined tectono-stratigraphic model of an extensional fault propagation fold is proposed here to explain such different deformation. In addition to the seabed escarpments produced by fault deformation, in the SEG, a strong control of fault activity on recent sedimentary processes is clearly observed. For example, canyons and channels frequently change their course in response to their interaction with main tectonic structures. Moreover, the upper branch of the Angitola Canyon shows straight flanks determined by fault scarps. Tectonics also determined different sediment accumulation rates and types of sedimentation (e.g., the accumulation of hanging wall turbidite deposits and the development of contourite deposits around the Maida Ridge). Furthermore, the distribution of landslides is often connected to main fault scarps and fluids are locally confined in the hanging wall side of faults and can escape at the seabed, generating pockmarks aligned along their footwall. • Active faults are imaged by multibeam bathymetry and seismic profiles. • Three main systems of faults affect the continental shelf and slope sectors. • A tectono-stratigraphic model of an extensional fault propagation fold is proposed. • Tectonic activity exerts a strong control on seabed morphology and recent processes. • Margin shaping results from the interplay between tectonic and non-tectonic factors. [ABSTRACT FROM AUTHOR]