Evaluation of Conjugate Stresses to Seth’s Strain Tensors

An explicit expression providing the symmetric stress tensor T(m) conjugate to the Seth’s strain measure E(m) for each integer m unequal 0 is presented. The result is obtained by exploiting an original approach for the solution of a tensor equation in the unknown T(m) expressed as function of the powers of the right stretch tensor U. The proposed approach is based upon the spectral decomposition of U and exploits some peculiar features of the set of fourth-order tensors obtained as linear combination of dyadic and square tensor products of the eigenprojectors of U. On the basis of such properties it is shown that the unknown T(m) can be expressed in the given reference frame as linear combination of six fourth-order tensors scaled through coefficients which are rational functions of the eigenvalues of U

High-resolution imaging of basin-bounding normal faults in the Southern Apennines seismic belt (Italy) by traveltime and frequency-domain full-waveform tomography

We apply a two-step seismic imaging flow by combined first-arrival traveltime and frequency-domain waveform tomographies to dense wide aperture data collected in the Val d’Agri basin (southern Italy). A large wavelength Vp model determined by first-arrival traveltime tomography is used as a starting model for waveform tomography. The multiscale waveform tomography consisting of successive inversion of increasing frequencies allows to progressively reconstruct the short wavelengths of the velocity model, providing valuable information on the Quaternary basin and on range-bounding normal-faulting systems

Diagnosis of centrocestus formosanus infection in zebrafish (Danio rerio) in Italy: A window to a new globalization-derived invasive microorganism

Centrocestus formosanus is a digenetic trematode with a complex life cycle, involving invertebrate and vertebrate hosts, humans included. In particular, it causes gill lesions and mortality in freshwater fish species, and gastrointestinal symptoms in infected humans. Here, we describe the occurrence of C. formosanus infection in zebrafish imported in Italy and propose a newly designed species-specific primer pair to ameliorate the diagnostic investigations for C. formosanus. Gill arches of 30 zebrafish were examined for the presence of encysted metacercariae under a stereomicroscope and processed through molecular analyses targeting the ribosomal internal transcribed sequence 2 (ITS2). Although C. formosanus distribution was originally restricted to Asia, it has been subsequently reported in new countries, revealing itself as an invasive species and raising important concerns for biodiversity, economy, scientific research, as well as animal and public health. Given the crucial role played by the ornamental fish industry in spreading this parasite, there is an urgent need for control measures to prevent the introduction and establishment of C. formosanus in non-endemic areas, including Europe. We also suggest developing new strategies in microbiology and epidemiology to better explore this new globalization-derived invasive species

From 3D to 4D passive seismic tomography: The sub-surface structure imaging of the Val d’Agri region, southern Italy

Local earthquakes (passive seismic) tomography (LET) is a well established tool for the imaging of the sub-surface structure. Alternative to active seismics, the main advantages of using natural sources are the better sounding in deeper portions of the upper crust, the relatively low cost, and the direct availability of S-waves. The main drawback is the achievable model resolution, which is limited by the density of the seismic network and the distribution of elastic sources, rather than the elastic wave frequency. Recently, 4D variations (in space and time) of velocity anomalies have been recognized in active volcanoes (Patanè et al., 2006) and normal faulting systems and ascribed to the medium response to transient geological processes, like dyke intrusions or fluid pressure increase on fault planes. In this paper we show how LET contributes to the imaging of the upper crust in a very attractive region like the Val d’Agri in southern Italy, which hosts both significant oil fields and seismogenic structures. We show that LET allows to improve the definition of the crust structure, at depths larger than those sampled by conventional seismic profiles, and detect the space-time dependency of elastic properties in response to local variations of fluid pressur

Radiography of a normal fault system by 64,000 high-precision earthquake locations: The 2009 L'Aquila (central Italy) case study

We studied the anatomy of the fault system where the 2009 L'Aquila earthquake (M_W 6.1) nucleated by means of ~64 k high-precision earthquake locations spanning 1 year. Data were analyzed by combining an automatic picking procedure for P and S waves, together with cross-correlation and double-difference location methods reaching a completeness magnitude for the catalogue equal to 0.7 including 425 clusters of similar earthquakes. The fault system is composed by two major faults: the high-angle L'Aquila fault and the listric Campotosto fault, both located in the first 10 km of the upper crust. We detect an extraordinary degree of detail in the anatomy of the single fault segments resembling the degree of complexity observed by field geologists on fault outcrops. We observe multiple antithetic and synthetic fault segments tens of meters long in both the hanging wall and footwall along with bends and cross fault intersections along the main fault and fault splays. The width of the L'Aquila fault zone varies along strike from 0.3 km where the fault exhibits the simplest geometry and experienced peaks in the slip distribution, up to 1.5 km at the fault tips with an increase in the geometrical complexity. These characteristics, similar to damage zone properties of natural faults, underline the key role of aftershocks in fault growth and co-seismic rupture propagation processes. Additionally, we interpret the persistent nucleation of similar events at the seismicity cutoff depth as the presence of a rheological (i.e., creeping) discontinuity explaining how normal faults detach at depth

Radiography of a normal fault system by 64,000 high-precision earthquake locations: The 2009 L’Aquila (central Italy) case study

We studied the anatomy of the fault system where the 2009 L’Aquila earthquake (MW 6.1) nucleated by means of ~64 k high-precision earthquake locations spanning 1 year. Data were analyzed by combining an automatic picking procedure for P and S waves, together with cross-correlation and double-difference location methods reaching a completeness magnitude for the catalogue equal to 0.7 including 425 clusters of similar earthquakes. The fault system is composed by two major faults: the high-angle L’Aquila fault and the listric Campotosto fault, both located in the first 10 km of the upper crust. We detect an extraordinary degree of detail in the anatomy of the single fault segments resembling the degree of complexity observed by field geologists on fault outcrops. We observe multiple antithetic and synthetic fault segments tens of meters long in both the hanging wall and footwall along with bends and cross fault intersections along the main fault and fault splays. The width of the L’Aquila fault zone varies along strike from 0.3 km where the fault exhibits the simplest geometry and experienced peaks in the slip distribution, up to 1.5 km at the fault tips with an increase in the geometrical complexity. These characteristics, similar to damage zone properties of natural faults, underline the key role of aftershocks in fault growth and co-seismic rupture propagation processes. Additionally, we interpret the persistent nucleation of similar events at the seismicity cutoff depth as the presence of a rheological (i.e., creeping) discontinuity explaining how normal faults detach at depth

Critical Behavior of a Three-State Potts Model on a Voronoi Lattice

We use the single-histogram technique to study the critical behavior of the three-state Potts model on a (random) Voronoi-Delaunay lattice with size ranging from 250 to 8000 sites. We consider the effect of an exponential decay of the interactions with the distance,$J(r)=J_0\exp(-ar)$, with $a>0$, and observe that this system seems to have critical exponents $\gamma$ and $\nu$ which are different from the respective exponents of the three-state Potts model on a regular square lattice. However, the ratio $\gamma/\nu$ remains essentially the same. We find numerical evidences (although not conclusive, due to the small range of system size) that the specific heat on this random system behaves as a power-law for $a=0$ and as a logarithmic divergence for $a=0.5$ and $a=1.0$Comment: 3 pages, 5 figure

Fault structure and slip localization in carbonate-bearing normal faults: An example from the Northern Apennines of Italy

Carbonate-bearing normal faults are important structures for controlling fluid flow and seismogenesis within the brittle upper crust. Numerous studies have tried to characterize fault zone structure and earthquake slip processes along carbonate-bearing faults. However, due to the different scales of investigation, these studies are not often integrated to provide a comprehensive fault image. Here we present a multi-scale investigation of a normal fault exhumed from seismogenic depths. The fault extends for a length of 10 km with a maximum width of about 1.5 km and consists of 5 sub-parallel and interacting segments. The maximum displacement (370e650 m) of each fault segment is partitioned along sub-parallel slipping zones extending for a total width of about 50 m. Each slipping zone is characterized by slipping surfaces exhibiting different slip plane phenomena. Fault rock development is controlled by the protolith lithology. In massive limestone, moving away from the slip surface, we observe a thin layer (<2 cm) of ultracataclasite, cataclasite (2e10 cm) and fault breccia. In marly limestone, the fault rock consists of a cataclasite with hydrofractures and smectite-rich pressure solution seams. At the micro-nanoscale, the slip surface consists of a continuous and thin (<300 mm) layer composed of coarse calcite grains (~5e20 mm in size) associated with sub-micrometer grains showing fading grain boundaries, voids and/or vesicles, and suggesting thermal decomposition processes. Micrometer-sized calcite crystals show nanoscale polysynthetic twinning affected by the occurrence of subgrain boundaries and polygonalized nanostructures. Investigations at the kilometres-tens of meter scale provide fault images that can be directly compared with high-resolution seismological data and when combined can be used to develop a comprehensive characterization of seismically active fault structures in carbonate lithologies. Micro and nanoscale investigations along the principal slipping zone suggest that different deformation processes, including plastic deformation and thermal decomposition, were active during seismic slip

The 2009 L’Aquila (Central Italy) Seismic Sequence.

On April 6 (01:32 UTC) 2009 a MW 6.1 normal faulting earthquake struck the axial area of the Abruzzo region in Central Italy. The earthquake heavily damaged the city of L’Aquila and its surroundings, causing 308 casualties, 70,000 evacuees and incalculable losses to the cultural heritage. We present the geometry of the fault system composed by two main normal fault planes, reconstructed by means of seismicity distribution: almost 3000 events with ML≥1.9 occurred in the area during the 2009. The events have been located with a 1D velocity model we computed for the area by using data of the seismic sequence. The mainshock, located at around 9.3 km of depth beneath the town of L’Aquila, activated a 50° (+/- 3) SW-dipping and ~135° NW-trending normal fault with a length of about 16 km. The aftershocks activated the whole 10 km of the upper crust up to the surface. The geometry of the fault is coherent with the mapped San Demetrio-Paganica and Mt. Stabiata normal faults. The whole normal fault system that reached about 50 km of length by the end of December in the NW-trending direction, was activated within the first few days of the sequence when most of the energetic events occurred. The main shock fault plane was activated by a foreshock sequence culminated with a MW 4.0 on the 30th of March (13:38 UTC), showing extensional kinematic with a minor left lateral component. The second major structure, located to the north close to Campotosto village, is controlled by a MW 5.0 which occurred on the same day of the main shock (the 6th of April at 23:15 UTC) and by a MW 5.2 event (9th of April - 00:53 UTC). The fault plane shows a shallower dip angle with respect to the main fault plane, of about 35° with a tendency to flattening towards the deepest portion. Due to the lack of seismicity above 5 km depth, the connection between this structure and the mapped Monti della Laga fault is not straightforward. This northern segment is recognisable for about 12-14 km of length, always NW-trending and forming a right lateral step with the main fault plane. The result is a en-echelon system overlapping for about 6 km. Seismicity pattern also highlights the activation of numerous minor normal fault segments within the whole fault system. The deepest is located at around 13-15 km of depth, south of the L’Aquila mainshock, and it seems to be antithetic to the main fault plane

The 2009 L'Aquila (central Italy) seismic sequence

On April 6 (01:32 UTC) 2009 a MW 6.1 normal faulting earthquake struck the axial area of the Abruzzo region in central Italy. The earthquake heavily damaged the city of L’Aquila and its surroundings, causing 308 casualties, 70,000 evacuees and incalculable losses to the cultural heritage. We present the geometry of the fault system composed of two main normal fault planes, reconstructed by means of seismicity distribution: almost 3000 events with ML≥1.9 occurred in the area during 2009. The events have been located with a 1D velocity model we computed for the area by using data of the seismic sequence. The mainshock, located at around a 9.3 km depth beneath the town of L’Aquila, activated a 50° (+/- 3) SW-dipping and ~135° NW-trending normal fault with a length of about 16 km. The aftershocks activated the whole 10 km of the upper crust up to the surface. The geometry of the fault is coherent with the mapped San Demetrio-Paganica and Mt. Stabiata normal faults. The whole normal fault system that reached about 40 km of length by the end of December in the NW-trending direction, was activated within the first few days of the sequence when most of the energetic events occurred. The main shock fault plane was activated by a foreshock sequence that culminated with a MW 4.0 on March 30 (13:38 UTC), showing extensional kinematics with a minor left lateral component. The second major structure, located to the north close to Campotosto village, is controlled by an MW 5.0 event, which occurred on the same day of the main shock (April 6 at 23:15 UTC), and by an MW 5.2 event (April 9 at 00:53 UTC). The fault plane shows a shallower dip angle with respect to the main fault plane, of about 35° with a tendency to flattening towards the deepest portion. Due to the lack of seismicity above a 5 km depth, the connection between this structure and the mapped Monti della Laga fault is not straightforward. This northern segment is recognisable for about 12-14 km of length, always NW-trending and forming a right lateral step with the main fault plane. The result is a en-echelon system overlapping for about 6 km. The seismicity pattern also highlights the activation of numerous minor normal fault segments within the whole fault system. The deepest is located at around a 13-15 km depth, south of the L’Aquila mainshock, and it seems to be antithetic to the main fault plane