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In this paper, we separate the residuals of ground motion prediction equations into different components, calculating the repeatable site-specific ( $$\delta S2S_{s}$$ ), location-specific ( $$\delta L2L_{r}$$ ) and path-specific ( $$\delta P2P_{er}$$ ) correction for the median model. In this way, we can reduce the total standard deviation (sigma) of the ground-motion model by Lanzano et al. (Bull Seismol Soc Am 106(1):73-92, 2016), removing these components and overcome the ergodic assumption. These repeatable terms are empirically estimated using a dataset composed by acceleration waveforms of Italian events mainly occurred in the Po plain and Eastern Alps (Northern Italy), in the time interval 1976-2015. The analysis is carried out on 2241 recordings, from 88 shallow earthquakes recorded by 168 sites. A local model, specifically tailored for Northern Italy, is used as the reference GMPE, which predicts the geometric mean of the horizontal peak ground accelerations and response spectral ordinates in the period range 0.04-4 s. Because most of the propagation paths sampled only once, the path-specific components and the resulting aleatory variability are also calculated from the spatial correlation of residuals, following the approach of Lin et al. (Bull Seismol Soc Am 101(5):2281-2295, 2011). We find a significant reduction of the overall ground motion variability to an extent comparable to what observed from previous studies on empirical and simulated datasets. The estimated median corrections and variance components can be used in probabilistic seismic hazard assessment for a single site and a single path in Northern Italy. As an example, we compute the hazard curves at some sites by means of three different approaches (ergodic, partially non-ergodic and full non-ergodic), in order to quantify the impact of relaxing the ergodic assumption. [ABSTRACT FROM AUTHOR]

Abstract: Background: Earthquakes are one of the most frequently occurring natural disasters and extensive research has been conducted on mental disorders on exposed populations, particularly on post-traumatic stress disorder (PTSD). On April 6th 2009, the town of L''Aquila (Abruzzo), in central Italy, was struck by an earthquake with a strength of 5.9 on the Richter scale. In the town of L''Aquila many buildings collapsed and large parts of the town were destroyed. Overall, 309 people were killed, 1600 injured among which 200 severely injured and hospitalized, more than 65,000 people were displaced. Methods: The aim of the present study was to investigate prevalence rates of PTSD, either full-blown or partial PTSD, among 512 students attending the last year of high school in L''Aquila about 10months after the earthquake. According to the literature, partial PTSD was defined as the presence of symptoms in the DSM-IV Criterion B and C or D for PTSD diagnosis. Gender differences in the symptoms reported were investigated. Assessments included the Trauma and Loss Spectrum-Self Report (TALS-SR) and the Impact of Event Scale (IES). Results: The results of the present study showed the presence of a diagnosis of PTSD in 192 (37.5%) of the students examined, with significantly (p =.000) higher rates in women than men (N =120, 51.7% and N =72, 25.7%, respectively). Moreover, 153 (29.9%) students reported partial PTSD (75, 32.3% women and 78, 27.9% men respectively). Significantly higher PTSD symptoms were reported by women with respect to men. Limitations: The lack of information on the impact of the earthquake on subjects and on the presence of Axis I psychiatric comorbidities are two major limitations besides the use of self-report instruments. Conclusions: Our results show high rates of full or partial PTSD in adolescents who survived the April 2009 L''Aquila earthquake, with women being the most affected. Thus, these results highlight the need to carefully explore these conditions. [Copyright &y& Elsevier]

We derive S-wave attenuation characteristics, earthquake source parameters and site amplification functions at seismic stations used for earthquake early warning in the Irpinia-Basilicata region, using non-parametric spectral inversion of seismograms from 49 local events with M = 1.5-3.1. We obtain relatively low Q values ( Q = 28 at a frequency of 1 Hz) in conjunction with a strong frequency-dependence (close to linear). The source spectra can be satisfactorily modeled using the omega-square model, with stress drops ranging between 0.01-2 MPa, and in the narrow magnitude range available for analysis, the source spectra seem to scale self-similarly. The local magnitude M shows a linear correlation with moment magnitude M, however with a systematic underestimation by about 0.5-magnitude units. The results obtained in this work provide important insights into the ground-motion characteristics that are required for appropriate seismic hazard assessment and are of practical relevance for a suite of applications, such as the calibration of ground-motion prediction equations or the correction for site amplification in earthquake early warning and rapid calculation of shake-maps for seismic emergency management. [ABSTRACT FROM AUTHOR]

We simulated strong-motion records from the Umbria-Marche, central Italy, earthquake (Mw 6) of September 1997 using a frequency-dependent S-wave radiation function. We compared the observed acceleration spectra, from strong-motion instruments located in the near field and at regional distances, with those simulated using the stochastic modeling technique of Beresnev and Atkinson (1997, 1998), and modified to account for a frequency-dependent radiation pattern correction. By using the frequency-dependent radiation function previously obtained by Castro et al. (2006), we reduced the overall fitting error of the acceleration spectra by about 9%. In general, we observed that the frequency-dependent radiation pattern correction has a small effect on the spectral amplitudes compared with site effects, which is an important factor controlling the strong-motion records generated by the 1997 Umbria-Marche earthquake. In addition, we modeled the observed ground-motion records using the dynamic corner frequency model of Motazedian and Atkinson (2005) to reproduce the directivity effects, reducing the average error of the spectral amplitudes by 24%. We concluded that although the frequency-dependent radiation pattern correction affects the frequency content of the spectral amplitudes simulated, site and directivity effects are more relevant. [ABSTRACT FROM AUTHOR]

Strombolian-type eruptive activity, common at many volcanoes, consists of regular explosions driven by the bursting of gas slugs that rise faster than surrounding magma. Explosion quakes associated with this activity are usually localized at shallow depth; however, where and how slugs actually form remain poorly constrained. We used spectroscopic measurements performed during both quiescent degassing and explosions on Stromboli volcano (Italy) to demonstrate that gas slugs originate from as deep as the volcano-crust interface (∼3 kilometers), where both structural discontinuities and differential bubble-rise speed can promote slug coalescence. The observed decoupling between deep slug genesis and shallow (∼250-meter) explosion quakes may be a common feature of strombolian activity, determined by the geometry of plumbing systems. [ABSTRACT FROM AUTHOR]

A spectral analysis of strong-motion data and ambient noise at the Tolmezzo-Ambiesta dam accelerograph (TLM1) site is performed to explain the high horizontal peak acceleration of 0.36g recorded during the Mw 6.4, 6 May 1976 Friuli (northeastern Italy) earthquake. The spectral response of the accelerographic site is estimated from the mainshocks and aftershocks of the 1976 seismic sequence by different techniques. In addition, new seismic data are used to characterize the near-surface S-wave velocity distribution versus depth at TLM1 by means of an analysis of the phase-velocity dispersion of Rayleigh waves. An average, spectral amplification curve is computed for TLM1, whose mean value is at about 1.5. It features two main lobes of amplification with peaks at 2-3.5 Hz and 6-7 Hz that are explained, by the horizontal-to-vertical spectral ratio (HVSR) of noise measurements, as the effects of the vibration of a nearby relief and the dam-reservoir system, respectively. When the site response is evaluated from earthquake recordings, the frequency of resonance due to near-surface S-wave velocity profile at about 5 Hz is strongly attenuated in comparison with the 6-7 Hz peak due to the dam-reservoir system. Finally, by filtering the site effects of the 1976 record, the acceleration peak is reduced from the original value of 349.99 cm/sec² to 188.76 cm/sec². [ABSTRACT FROM AUTHOR]

We computed the source parameters of 135 local earthquakes that occurred in southeastern Sicily (Italy) between 1994 and 2001. Magnitudes ranged from 0.6 to 2.5. The source parameters were determined from the spectral analysis of P waves, alter corrections for attenuation and site effects. P-wave quality (QP) and site (S) factors are known in the two frequency ranges 3-9 Hz and 16-27 Hz (Giampiccolo et al., 2003). Because the correction for QP and S over the whole spectrum could not be performed, a new approach to estimate spectral parameters was applied. We defined the new notion of "holed spectrum" to specify a spectrum lacking corrected spectral amplitude values within a certain frequency range, whereas we referred to a "whole spectrum" to specify when the entire analyzed frequency band was used. A detailed statistical analysis showed that dealing with the holed spectrum did not lead to significant differences in the estimate of spectral parameters. Displacement holed spectra, corrected by the attenuation and site response, were then used to estimate source parameters. Seismic moments ranged from 1017 to 1020 dyne cm, and source dimensions from 150 to 500 m. In general, the stress-drop values obtained analyzing P-wave spectra were very low, because they mainly span the range of 0.05-5 bars. [ABSTRACT FROM AUTHOR]

Evidence of complex site effects in two-dimensional geological configurations is illustrated first, and the related difficulties in interpreting ground motion observations are discussed, using weak motion data recorded in three alpine valleys in Northern Italy. While, on one hand, such valleys are mostly located in regions of low or moderate seismic hazard, where ground motion data are scarce, on the other hand investment in buildings and infrastructure has been substantial and may not always have been protected by adequate earthquake-resistant provisions and zoning criteria. Moreover, experience and data obtained in regions hit by destructive earthquakes cannot be easily transferred to such a different context. The combined influence of one-dimensional propagation effects on the dominant frequencies of motion, and of two-dimensional effects on the amplification level and significant frequency band, are highlighted. Concerning design elastic spectra, estimates of response spectra on hard and soft soil are performed, using observed weak motion data and the empirical Green's functions method. Comparison of results with Eurocode 8 spectra shows that the latter may not be conservative at periods larger than 1 s. The relatively large response at such is related to the geological configuration of the valleys, which appear to require a reasonably accurate definition of their two-dimensional geometry. [ABSTRACT FROM AUTHOR]