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The site-corrected source scaling pattern is estimated for local earthquakes (0.9 ≤ MD ≤ 3.6) at Mt. Vesuvius. The dataset comprises 35 low-to-moderate local earthquakes recorded by 14 three-component seismic stations during 1993, 1996, and 1999. Site-transfer functions in the frequency range 1 Hz-25 Hz are estimated from the spectra of S waves and coda waves and from the horizontal-to-vertical (H/V) spectral ratios. We applied the direct spectral ratios method to S waves, considering as a reference the average spectrum and the inversion method to S waves and coda waves. The site amplification on the coda waves was also compared with that evaluated using the wavelet transform. The standard deviation associated with the experimental results is computed for all of the used methods. Results indicate a general agreement among the methods, and the site-transfer functions show interesting features. The highest amplifications are found for frequencies lower than 12 Hz for sites located at lower altitude. The methods based on coda waves show highest amplification with respect to the methods based on S waves for most of the sites located in the summit part of the volcano. This can be a phenomenon of coda localization, which consists in the trapping inside the upper part of the volcano of scattered waves. The H/V spectral ratios do not show total agreement with the other methods, mostly for the sites located in the summit part of the volcano. The discrepancies among the results obtained in this work are also due to the different normalization applied in the methods of analysis. Generalized inversion method allowed us to estimate the source scaling of the site-corrected source seismic spectrum for the investigated area. The source scaling obtained in terms of seismic moment and source radii shows that the seismicity of Mt. Vesuvius is characterized by stress drop as low as a few bars (10 bars) except for the event of MD 3.6 (Δσ = 100 bars). The scaling pattern shows an apparent linear relationship between source size and seismic moment (for MD ≤ 3.3) but the statistical test shows that the linear trend has low reliability. [ABSTRACT FROM AUTHOR]

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-tomoderate 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 yr before the eruption of Mt. Vesuvius that occurred in A.D. 79. The largest values of Amax for the MD 4.3 seismic event are in the range of 0.140g-0.029g. In the case of MD 5.4, we obtain peak ground acceleration values in the range between 0.17g and 0.55g. [ABSTRACT FROM AUTHOR]