Stochastic Finite-Fault Ground Motion Simulation in a Wave Field Diffusive Regime: Case Study of the Mt. Vesuvius Volcanic Area

The main aim of the present work consists in the validation of stochastic method for simulating weak ground motion in a diffusive regime due to low-to-moderate magnitude earthquakes, and in particular in its application to a volcanic area. We simulated the peak ground acceleration and the response acceleration spectra caused by two earthquakes scenarios (MD = 4.3 and MD = 5.4) at Mt. Vesuvius volcanic area by using the stochastic finite-fault simulation method. We validated the stochastic methodology by combining source, path and site parameters of the investigated area considering the time duration parameter, Trms, calculated on the study seismograms. The values of time durations are confirmed by calculating the same parameter, Trms, on the seismogram energy envelope described by multiple scattering models, in terms of scattering and the intrinsic dissipation coefficient. Initially, the simulations were evaluated for 10 local earthquakes (1.7 ≤ MD ≤ 3.6) that occurred at Mt Vesuvius in 1999 and are then compared with the observed data. The comparison between simulated and observed seismograms has been used to calibrate the stochastic procedure, and has been considered as the starting point for simulating ground motion for the scenario earthquake (MD > 3.6) that could occur in the study area. The scenario earthquake and the relative fault features were chosen on the base of statistical, tectonic, structural and historical studies of the study area. We simulated ground motions for a maximum magnitude value, Mmax, of 4.3, determined from examination of the Gutenberg-Richter law for the study area, and also for an Mmax = 5.4, a magnitude that is associated with the earthquakes that struck the ancient town of Pompei 17 years before the eruption of Mt Vesuvius that occurred in 79 AD. The largest values of Amax for the MD = 4.3 seismic event are in the range of 0.140 g to 0.029 g. In the case of MD = 5.4, we obtain PGA values in the range between 0.17 and 0.55 g

Site effects Estimation and Source_Scaling Dynamics for Local Earthquakes at Mt. Vesuvius, Italy

Local microearthquakes were used to estimate site effects and source dynamic-scaling characteristics at Mt. Vesuvius, Italy. The selected data set is composed of low magnitude events (1.1 £ Md £ 3.6) recorded in 1996 and 1999 by nine digital shortperiod (1-Hz) seismic stations. Site response was evaluated by analysing data with three different approaches: 1) spectral ratios method of S-waves with respect to the average amplitude spectrum; 2) generalized inversion for site and source from the S-waves; and 3) generalized inversion from the coda waves. The results obtained with all three methods showed amplification of a factor of 1.5-2.5 in the 8-14 Hz frequency band for BKE and SGV sites and an amplification of 3 in a narrow band around 8 Hz for the CDT site. Method 2 allowed simultaneous determination of the source spectral shape for each earthquake. By assuming an w2 source model, we estimated the seismic moment Mo and corner frequency fc. The results show that most of the selected earthquakes are characterized by stress drops of 10 bars. The present results are encouraging for further investigation into the techniques for site-effect evaluation and for improving our knowledge of the scaling law of the source spectrum at Mt. Vesuvius

Application of the spac method to ambient noise recorded in the vesuvius area (italy)

Noise measurements were recorded using a dense short-period seismic array in Terzigno (Naples), a town that is located about 6 km from the Vesuvius crater. The aim of this study was to calculate a surface velocity model of the area under investigation through the application of the Spatial Autocorrelation (SPAC) method, with the hypotheses that ambient noise is stationary both in time and space, and that it is composed of surface dispersive waves. The correct knowledge of the surface structure is an important goal in site-effects studies. Correlation coefficients were calculated as functions of the azimuth on noise recorded at pairs of equally spaced stations in the frequency range of 1-8 Hz. Then, the spatial average correlation coefficients were compared to estimates over long-term recordings. The results appear to validate the hypothesis that ambient noise can be considered as a stochastic process. The correlation-frequency curves have been fitted to Bessel functions, from which the Rayleigh wave dispersion curve has been calculated. A velocity model has been derived from the dispersion curve using both trial and error and a standard inversion procedure. The results are consistent with those obtained from array measurements in the area in other studies (Scarpa et al., 2003)

Numerical modeling of bifacial PV string performance: Perimeter effect and influence of uniaxial solar trackers

The bifacial photovoltaic (PV) systems have recently met large interest. The performance of such systems heavily depends on the installation conditions and, in particular, on the albedo radiation collected by the module rear side. Therefore, it is of crucial importance to have an accurate performance model. To date, in the scientific literature, numerous models have been proposed and experimental data collected to study and optimize bifacial PV system performance. Currently, 3D and 2D models of bifacial PV devices exist. Though the former are more mathematically complex, they can lead to more accurate results, since they generally allow to fully consider the main aspects influencing a bifacial PV system performance. Recently, we have proposed and validated through experimental data a 3D model tested as a function of module height, tilt angle, and ground albedo. In this work, through such a model, we studied the role played by the perimeter zones surrounding the PV string, by considering PV strings of 30 or 60 modules. We considered the cases of fixed installation with optimal PV module tilt and of installation with uniaxial horizontal solar tracker. We evaluated the PV energy yield as a function of the size of the perimeter zones for the two cases, i.e., both with and without the solar tracker. In optimal perimeter conditions, we then studied the behavior of bifacial and mono-facial PV strings by varying the geographical location in a large latitude range

Imaging the buried rim of Campi flegrei caldera (Italy) from array analysis

On September an extended active seismic survey(SERAPIS,Seismic Reflection Acquisition Project for Imaging Structure)was conducted in the Gulf of Naples and Pozzuoli with the aimof providing new insights on the Campi Flegrei caldera structure and of investigating its feeding system(fig.1).About3000air-gunsea-shots were shot(fig.3a,b,c).In the frame work of this project,anarray of 28 vertical-component and 4 three component sensors was deployed in the Solfatara crater(fig.2).The array had an aperture of about 200m,and receivers had a natural frequency of 1Hz.An example of the recorded wave forms is shown in figure 4

Patterns of Brain Structural Changes in First-Contact, Antipsychotic Drug-Naïve Patients with Schizophrenia

BACKGROUND AND PURPOSE: Previous studies have suggested that structural changes do occur in the brain of patients with schizophrenia compared with healthy control participants. However, findings from such studies are inconclusive, probably because of the different methodologic approaches, the clinical heterogeneity of patient samples, and also the fact that patients enrolled were treated with antipsychotic drugs. The aim of this study was to investigate brain GM volumes and intrinsic structural WM changes in first-contact, antipsychotic drug-naive patients with schizophrenia. MATERIALS AND METHODS: A total of 43 first-contact, drug-naive, patients with schizophrenia and 17 age-matched control participants were studied. All participants underwent T1-weighted MR imaging and DTI scans. Voxel-based morphometry and tract-based spatial statistics were used to compare GM volumes and WM DTI metrics between groups. MR imaging measures were correlated with the duration of the untreated psychosis and the clinical positive and negative symptoms. RESULTS: Compared with control participants, patients with schizophrenia showed smaller volumes of the temporal, parietal, and occipital GM, and a pattern of decreased mean diffusivity and increased fractional anisotropy in the brain stem and cerebellum bilaterally, interhemispheric and cortico-cortical connections bilaterally, and right anterior and posterior limb of the internal capsule. In patients, decreased mean diffusivity and increased fractional anisotropy in several brain regions were related to a longer duration of the untreated psychosis and the severity of positive symptoms. CONCLUSIONS: First-contact, drug-naive, patients with schizophrenia present with volumetric and DTI changes, which correlated with their clinical features. This study increases our knowledge on the neural networks involved in the pathophysiologic mechanisms of schizophrenia

Trace elements in stomach oil of Scopoli's shearwater (Calonectris diomedea) from Linosa's colony

Calonectris diomedea is a colonial Procellariiform breeding on Mediterranean islands. The stomach oil produced during chick rearing is a peculiar trait of this species. The composition of the stomach oil is likely to reflect the composition of the prey ingested and might reveal the contaminants uptake with prey becoming a possible tool for the marine pollution monitoring. We examined the concentration of 15 trace elements by ICP-MS and direct mercury analyser. The principal component analysis revealed a heterogeneous pattern of metal concentration, showing a significant separation between samples collected 20 and 70 days after hatching. The data obtained in this work give preliminary information on the feeding habits and breeding ecology of Linosa's colony of Scopoli's shearwater. The trace metals variability found suggest that the stomach oil may have a role as trophic markers to understand predator-prey relationships and to have evidence on the accumulation of pollutants in the latter

Site Amplification map of Campi Flegrei and Vesuvius estimated from the combined analysis of Lithological and Seismological information

Seismic stations used for the site analysis. • Site Transfer functions resulted from the two different techniques: Generalized Inversion Technique (GIT) and Horizontal to Vertical Spectral Method. • Definition of homogeneous areas using the geological information. • Site amplification maps obtained for different frequency bands. All these analysys are done both for Vesuvius and Campi Flegre