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In this study, we investigate the correlation between the residuals of a neGMM (non-ergodic Ground Motion Model) and the physics-based parameters obtained using a non-parametric GIT approach (Generalized Inversion Technique) to lay the groundwork for the implementation of an ad-hoc FAS (Fourier Amplitude Spectra) neGMM for the Central Italy region. This region is particularly suitable for data-driven methodologies as those applied in this work because of the large amount of available data due to the recent multiple main shock–aftershock sequences occurred in this area. Both neGMM and GIT models are developed for Fourier spectra in the frequency range between 0.5 and 25 Hz and using the same reference sites. The comparison of the non-ergodic terms with the source, path and site spectral parameters provides interesting results. First, we find a strong correlation between the source parameters, stress drop Δσ and decay |${k}_{\mathrm{ source}}$| and the source neGMM corrective terms (the combination of the between-event δBe and the location-to-location terms δL2L). This correlation is frequency dependent and, at high frequency, is remarkably positive for Δσ and negative for |${k}_{\mathrm{ source}}$|⁠. Concerning the attenuation terms, the path-to-path residuals (δP2P) are clearly associated with the deviations from the regional Q estimates obtained from GIT analysis. This indicates that the neGMM properly captures the properties of the anelastic attenuation and that the corrective terms δP2P can be used to account for differences in travel paths across different crustal domains. Finally, adopting the same reference sites for neGMM and non-parametric GIT, we observe that the systematic site terms (δS2Ss) and the GIT-derived amplification functions are in good agreement. The next step for an appropriate modelling is to identify the physical parameters (e.g. VS,30 and |${k}_0$|⁠) describing the empirical amplification curves to be introduced as explanatory variables in the ground motion model. [ABSTRACT FROM AUTHOR]

We investigate the preparatory phase of the 2009, Mw 6.1 L'Aquila earthquake in central Italy by analyzing the temporal evolution and spatial distribution of the seismic moment, M0, to radiated energy, ES. Our approach focuses on monitoring the deviations of the scaling between M0 and ES with respect to a model calibrated for the background seismicity. The temporal evolution of these deviations, defined as Energy Index (EI), identifies the onset of the activation phase 1 week before the mainshock. We show that foreshocks are characterized by a progressive increase in slip per unit stress, in agreement with the diffusion of highly pressurized fluids before the L'Aquila earthquake proposed by previous studies. Our results suggest that the largest events occur where energy index (EI) is highest, in agreement with the existing link between energy index (EI) and the mean loading stress. Plain Language Summary: Understanding how the machine generating large earthquakes works is one of the fundamental challenging scientific questions. Pioneering studies have shown that large magnitude earthquakes are sometimes anticipated by foreshocks and slip instabilities. Until now, retrospective analyses of foreshocks during the preparatory phase of large earthquakes have focused mainly on their distribution in space, time and magnitude. In this study, we show that also the dynamic properties of the rupture process associated to foreshocks evolve both in time and space. Our results indicate that the temporal evolution of radiated energy and size of small magnitude earthquakes provide useful information to identify the begin of the final activation phase of the 2009 Mw 6.1 L'Aquila, Italy, earthquake, in agreement with seismicity rate information. Our study suggests that, for the investigated case, foreshocks had dynamic characteristics distinct from those of normal rate (background) seismicity. Thus, it can contribute with new evidence to the open debate whether foreshocks are different phenomena from background seismicity. Key Points: We observe foreshocks dynamic characteristics before the 2009, Mw 6.1 L'Aquila earthquake in central ItalyDeviations of radiated energy over seismic moment from a reference model highlight the preparatory phase of the main eventForeshocks are characterized by a progressive increase in slip per unit stress, in agreement with diffusion of highly pressurized fluids [ABSTRACT FROM AUTHOR]

The 2016–2017 central Italy earthquake sequence began with the first main shock near the town of Amatrice on August 24 (M w 6.0), and was followed by two subsequent large events near Visso on October 26 (M w 5.9) and Norcia on October 30 (M w 6.5), plus a cluster of four events with M w > 5.0 within few hours on 18 January 2017. The affected area had been monitored before the sequence started by the permanent Italian National Seismic Network (RSNC), and was enhanced during the sequence by temporary stations deployed by the National Institute of Geophysics and Volcanology and the British Geological Survey. By the middle of September, there was a dense network of 155 stations, with a mean separation in the epicentral area of 6–10 km, comparable to the most likely earthquake depth range in the region. This network configuration was kept stable for an entire year, producing 2.5 TB of continuous waveform recordings. Here we describe how this data was used to develop a large and comprehensive earthquake catalogue using the Complete Automatic Seismic Processor (CASP) procedure. This procedure detected more than 450 000 events in the year following the first main shock, and determined their phase arrival times through an advanced picker engine (RSNI-Picker2), producing a set of about 7 million P - and 10 million S -wave arrival times. These were then used to locate the events using a non-linear location (NLL) algorithm, a 1-D velocity model calibrated for the area, and station corrections and then to compute their local magnitudes (M L). The procedure was validated by comparison of the derived data for phase picks and earthquake parameters with a handpicked reference catalogue (hereinafter referred to as 'RefCat'). The automated procedure takes less than 12 hr on an Intel Core-i7 workstation to analyse the primary waveform data and to detect and locate 3000 events on the most seismically active day of the sequence. This proves the concept that the CASP algorithm can provide effectively real-time data for input into daily operational earthquake forecasts, The results show that there have been significant improvements compared to RefCat obtained in the same period using manual phase picks. The number of detected and located events is higher (from 84 401 to 450 000), the magnitude of completeness is lower (from M L 1.4 to 0.6), and also the number of phase picks is greater with an average number of 72 picked arrival for a M L = 1.4 compared with 30 phases for RefCat using manual phase picking. These propagate into formal uncertainties of ±0.9 km in epicentral location and ±1.5 km in depth for the enhanced catalogue for the vast majority of the events. Together, these provide a significant improvement in the resolution of fine structures such as local planar structures and clusters, in particular the identification of shallow events occurring in parts of the crust previously thought to be inactive. The lower completeness magnitude provides a rich data set for development and testing of analysis techniques of seismic sequences evolution, including real-time, operational monitoring of b -value, time-dependent hazard evaluation and aftershock forecasting. [ABSTRACT FROM AUTHOR]

We introduce in the on-site earthquake early warning (EEW) a partially non-ergodic perspective from the site effects point of view. We consider the on-site EEW approach where the peak ground velocity (PGV) for S waves is predicted from an early estimate, over the P waves, of either the peak-displacement (PD) or cumulative squared velocity (IV2). The empirical PD-PGV and IV2-PGV relationships are developed by applying a mixed-effect regression where the site-specific modifications of ground shaking are treated as random effects. We considered a large data set composed of almost 31 000 selected recordings in central Italy, a region struck by four earthquakes with magnitude between 6 and 6.5 since the 2009 L'Aquila earthquake. We split the data set into three subsets used for calibrating and validating the on-site EEW models, and for exemplifying their application to stations installed after the calibration phase. We show that the partially non-ergodic models improve the accuracy of the PGV predictions with respect to ergodic models derived for other regions of the world. Moreover, considering PD and accounting for site effects, we reduce the (apparent) aleatory variability of the logarithm of PGV from 0.31 to 0.36, typical values for ergodic on-site EEW models, to about 0.25. Interestingly, a lower variability of 0.15 is obtained by considering IV2 as proxy, which suggests further consideration of this parameter for the design of on-site EEW systems. Since being site-specific is an inherent characteristic of on-site EEW applications, the improved accuracy and precision of the PGV predicted for a target protection translate in a better customization of the alert protocols for automatic actions. [ABSTRACT FROM AUTHOR]

The size of an earthquake can be defined either from the seismic moment (M 0) or in terms of radiated seismic energy (E r). These two parameters look at the source complexity from different perspectives: M 0 is a static measure of the earthquake size, whereas E r is related to the rupture kinematics and dynamics. For practical applications and for dissemination purposes, the logarithms of M 0 and E r are used to define the moment magnitude M w and the energy magnitude M E, respectively. The introduction of M w and M E partially obscure the complementarity of M 0 and E r. The reason is due to the assumptions needed to define any magnitude scale. For example, in defining M w, the apparent stress (i.e. the ratio between M 0 and E r multiplied by the rigidity) was assumed to be constant, and under this condition, M w and M E values would only differ by an off-set which, in turn, depends on the average apparent stress of the analysed data set. In any case, when the apparent stress is variable and, for example, scales with M 0, the value of M E derived from M w cannot be used to infer E r. In this study, we investigate the similarities and differences between M w and M E in connection with the scaling of the source parameters using a data set of around 4700 earthquakes recorded at both global and regional scales and belonging to four data sets. These cover different geographical areas and extensions and are composed by either natural or induced earthquakes in the magnitude range 1.5 ≤ M w ≤ 9.0. Our results show that M E is better than M w in capturing the high-frequency ground shaking variability whenever the stress drop differs from the reference value adopted to define M w. We show that M E accounts for variations in the rupture processes, introducing systematic event-dependent deviations from the mean regional peak ground motion velocity scaling. Therefore, M E might be a valid alternative to M w for deriving ground motion prediction equations for seismic hazard studies in areas where strong systematic stress drop scaling with M 0 are found, such as observed for induced earthquakes in geothermal regions. Furthermore, we analyse the different data sets in terms of their cumulative frequency–magnitude distribution, considering both M E and M w. We show that the b values from M w (b Mw) and M E (b ME) can be significantly different when the stress drop shows a systematic scaling relationship with M 0. We found that b ME is nearly constant for all data sets, while b M w shows an inverse linear scaling with apparent stress. [ABSTRACT FROM AUTHOR]

Abstract: The 2016–2017 Central Italy seismic sequence ruptured overlapping normal faults of the Apennines mountain chain, in nine earthquakes with magnitude Mw > 5 within a few months. Here we investigate the structure of the fault system using an extensive aftershock data set, from joint permanent and temporary seismic networks, and 3‐D Vp and Vp/Vs velocity models. We show that mainshocks nucleated on gently west dipping planes that we interpret as inverted steep ramps inherited from the late Pliocene compression. The two large shocks, the 24 August, Mw = 6.0 Amatrice and the 30 October, Mw = 6.5 Norcia occurred on distinct faults reactivated by high pore pressure at the footwall, as indicated by positive Vp/Vs anomalies. The lateral extent of the overpressurized volume includes the fault patch of the Norcia earthquake. The irregular geometry of normal faults together with the reactivated ramps leads to the kinematic complexity observed during the coseismic ruptures and the spatial distribution of aftershocks. [ABSTRACT FROM AUTHOR]

In this study, we analyse a regional data set composed by about 9000 waveforms from 231 earthquakes in the magnitude range from 3 to 6 and recorded in central Italy in the time period 2008-2013. We derive a seismological model whose source, attenuation and site parameters are used to explain the ground motion variability associated with a set of ground motion prediction equation (GMPE) calibrated ad hoc for both Fourier and acceleration response spectra. The main results are the following: (1) the between-event residuals δBe show a clear dependence on the stress drop for frequencies above 2 Hz; (2) the standard deviation τ of δBe is strongly reduced (up to 80 per cent) by introducing in the functional form the stress drop values estimated from each source spectrum; (3) the standard deviation τ depends on the magnitude scale used to calibrate the GMPE: while the moment magnitude better describes the source variability at low frequency, the local magnitude better capture the source-related ground motion variability at frequencies larger than 2 Hz; (4) for frequencies higher than 10 Hz, the observed increase of τ with frequency correlate well with the attenuation parameter ksource, computed from the high-frequency slope of the source spectra. Regarding the station-to-station residuals δS2S, their frequency dependency is in good agreement with the site amplifications extracted from the S-wave spectra. Finally, while the overall dependences of the ground motion variability on seismological parameters are similar when observed either in the Fourier or in the response spectra domains (e.g. the dependency of the between event on stress drop), differences in the results suggest that the response spectra do not allow to fully capture the ground motion variability, as well as the site amplifications, at high frequencies. [ABSTRACT FROM AUTHOR]

This study compares 12 hazard models based on dated and recent ground-motion prediction equations (GMPEs) to evaluate the improvement provided by new equations on probabilistic seismic-hazard assessments in Italy. To this end, a statistical procedure is applied to score the outcomes of each hazard model at 56 different accelerometric sites that have been operating for at least 25 years. This procedure, which calculates the likelihood of the outcomes of the hazard models relative to available observations, evaluates the performance of each model and, indirectly, the influence of the selected GMPEs in providing effective hazard estimates. We have found that older GMPEs tend to yield high-frequency ground-motion hazard values that are overconservative at shorter mean return periods and underconservative at longer ones. To identify the sources of the different behavior between older and more recent equations, the biasing of each GMPE is evaluated by comparing median predictions with observations available at two accelerometric sites where a relatively large number of ground motions from different earthquakes have been recorded and local soil conditions are well established. Results indicate that two decades of research on GMPEs have resulted in a significant reduction of bias with an improvement in the accuracy of predictions. Major improvements have been observed from 2008 to 2010. These may be related to the increased completeness of regression data sets and to an increased effectiveness of functional forms, which allow a better modeling of the physical process governing the propagation of ground motions. Since then, the GMPE bias has remained almost stable and no significant improvement in the performances of the relative hazard models has been observed. Our results also indicate that worldwide GMPEs applied to Italy are less effective at providing hazard results corroborated by observations. [ABSTRACT FROM AUTHOR]

In this work, we test a fully automatic procedure to obtain local earthquake tomography (LET), starting from seismic waveforms and applying the capability of the automatic phase picker and locator engine "RSNI-Picker" (Spallarossa et al., 2014), which is based on a multistep iterative procedure working on P and S arrival times. This code is currently operating as part of the Earthquake Monitoring System at the University of Genoa (RSNI designates the regional seismic network of northwestern Italy). In particular, we compare P- and S-wave tomographic results obtained using this fully automatic procedure for picking and locations with those based on data from accurate manual picking and revised locations. We use a dataset of 409 earthquakes that occurred in the Trentino region (Northeastern Italy) in the 1994-2007 period. The highly variable waveform qualities (e.g., signal-to-noise ratio), mainly due to recording stations equipped with different types of sensors and digitizers (including both one-component narrowband stations and three-component broadband seismic stations), ensure a severe test for the automatic procedure. The comparison of the two 3D velocity propagation models for the Trentino region (i.e., LET images) from the automatic and manual procedures, shows maximum differences of 0.54 and 0.34 km/s for P and S waves, respectively (if we consider 90% of all the computed absolute velocities, as a reference percentage). The automatic LET shows velocity anomaly distributions and reliability patterns (e.g., resolution diagonal element [RDE] values) similar to those obtained using the manual procedure; 90% of RDE differences are lower than 0.15. The results obtained by testing the RSNI-Picker engine suggest it can be used to automatically process large amounts of seismic recordings in order to identify P and S wavepicks for reliable LET analysis. [ABSTRACT FROM AUTHOR]

In this study we derive a spectral model describing the source, propagation and site characteristics of S waves recorded in central Italy. To this end, we compile and analyse a high-quality data set composed of more than 9000 acceleration and velocity waveforms in the local magnitude (M1) range 3.0-5.8 recorded at epicentral distances smaller than 120 km. The data set spans the time period from 2008 January 1 to 2013 May 31, and includes also the 2009 L'Aquila (moment magnitudeMw 6.1,M1 = 5.8) sequence. This data set is suitable for the application of data-driven approaches to derive the empirical functions for source, attenuation and site terms. Therefore, we apply a non-parametric inversion scheme to the acceleration Fourier spectra of the S waves of 261 earthquakes recorded at 129 stations. In a second step, with the aim of defining spectral models suitable for the implementation in numerical simulation codes, we represent the obtained non-parametric source and propagation terms by fitting standard parametric models. The frequency-dependent attenuation with distance r shows a complex trend that we parametrize in terms of geometrical spreading, anelastic attenuation and highfrequency decay parameter k. The geometrical spreading term is described by a piecewise linear model with crossover distances at 10 and 70 km: in the first segment, the spectral ordinates decay as r-1.01 while in the second as r-1.68. Beyond 70 km, the attenuation decreases and the spectral amplitude attenuate as r-0.64. The quality factor Q(f) and the high-frequency attenuation parameter k, are Q(ƒ) = 290 ƒ0.16 and k = 0.012 s, respectively, the latter being applied only for frequencies higher than 10 Hz. The source spectra are well described by ω² models, from which seismic moment and stress drops of 231 earthquakes are estimated. We calibrate a new regional relationship between seismic moment and local magnitude that improves the existing ones and extends the validity range to 3.0-5.8. We find a significant stress drop increase with seismic moment for events with Mw larger than 3.75, with so-called scaling parameter ε close to 1.5. We also observe that the overall offset of the stress-drop scaling is controlled by earthquake depth. We evaluate the performance of the proposed parametric models through the residual analysis of the Fourier spectra in the frequency range 0.5-25 Hz. The results show that the considered stress-drop scaling with magnitude and depth reduces, on average, the standard deviation by 18 per cent with respect to a constant stress-drop model. The overall quality of fit (standard deviation between 0.20 and 0.27, in the frequency range 1-20 Hz) indicates that the spectral model calibrated in this study can be used to predict ground motion in the L'Aquila region. [ABSTRACT FROM AUTHOR]

The impact on probabilistic ground-motion hazard of different definitions of the horizontal component of ground shaking is examined. The scope is to highlight how such a minor detail within the complex computation chain of a probabilistic seismic- hazard assessment can play a crucial role on final results. This is achieved by comparing hazard maps produced for Italy considering different definitions of the groundmotion component at different spectral periods. In our exercise, special attention is paid to the treatment of the aleatory variability of ground motion (sigma) when one switches from one metric to another. The results show that differences in the definition of the horizontal component could imply differences in the hazard results as large as 40%. [ABSTRACT FROM AUTHOR]

A seismic hazard assessment is often thought of as a process that calculates the mean annual rates of exceeding given ground-motion values on rock at a specific location. However, in many applications this view is reductive. A more complete definition should account for the hazard due to other effects induced by seismic activity at a site, such as the effect of soil deposits (including cyclic mobility and liquefaction) and topography on surface ground-motion, and for sites on slopes and for those straddle by fault lines, the effects of slope instability and of possible tectonic movements along faults. Moreover, for some coastal sites the effects of tsunami waves, not discussed in this paper, should be taken into account. The aim of this article is to present an overview of different probabilistic methods for advanced site-specific seismic hazard applications based on an extensive literature review and authors' experience. Application to real cases is also presented and discussed. [ABSTRACT FROM AUTHOR]

In this study, microseism recordings from a near coast seismic station and concurrent significant sea wave heights ($H_{\frac{1}{3}}$) are analysed to calibrate an empirical relation for predicting sea wave height in the Ligurian Sea. The study stems from the investigation of the damaging sea storms occurred in the Ligurian Sea between 2008 October and November. Analysing data collected in this time frame allows identification of two types of microseism signal, one associated to the local sea wave motion and one attributable to a remote source area. The former is dominated by frequencies greater than 0.2 Hz and the latter by frequencies between 0.07 and 0.14 Hz. Moreover, comparison of microseism spectrogram and significant sea wave heights reveals a strong correlation in that the spectral energy content of microseism results proportional to the sea wave height observed in the same time window. Hence, an extended data set including also observations from January to December 2011 is used to calibrate an empirical predictive relation for sea wave height whose functional form is a modified version of the classical definition of $H_{\frac{1}{3}}$. By means of a Markov chain Monte Carlo algorithm we set up a procedure to investigate the inverse problem and to find a set of parameter values for predicting sea wave heights from microseism. [ABSTRACT FROM AUTHOR]

The goals of this work are to review the Northern-Italy ground-motion prediction equations (GMPEs) for amplitude parameters and to propose new GMPEs for frequency content and duration parameters. Approximately 10,000 weak and strong waveforms have been collected merging information from different neighboring regional seismic networks operating in the last 30 yr throughout Northern Italy. New ground-motion models, calibrated for epicentral distances ≤100 km and for both local (ML) and moment magnitude (Mw), have been developed starting from a high quality dataset (624 waveforms) that consists of 82 selected earthquakes with ML and Mw up to 6.3 and 6.5, respectively. The vertical component and the maximum of the two horizontal components of motion have been considered, for both acceleration (peak ground horizontal acceleration [PGHA] and peak ground vertical acceleration [PGVA]) and velocity (peak ground horizontal velocity [PGHV] and peak ground vertical velocity [PGVV]) data. In order to make comparisons with the most commonly used prediction equations for the Italian territory (Sabetta and Pugliese, 1996 [hereafter, SP96] and Ambraseys et al. 2005a,b [hereafter, AM05]) the coefficients for acceleration response spectra (spectral horizontal acceleration [SHA] and spectral vertical acceleration [SVA]) and for pseudovelocity response spectra (pseudospectral horizontal velocity [PSHV] and pseudospectral vertical velocity [PSVV]) have been calculated for 12 periods ranging between 0.04 and 2 sec and for 14 periods ranging between 0.04 and 4 sec, respectively. Finally, empirical relations for Arias intensities (IA), Housner intensities (IH), and strong motion duration (DV) have also been calibrated. The site classification based on Eurocode (hereafter, EC8) classes has been used (ENV, 1998, 2002). The coefficients of the models have been determined using functional forms with an independent magnitude decay rate and applying the random effects model (Abrahamson and Youngs, 1992; Joyner and Boore, 1993) that allow the determination of the interevent, interstation, and record-to-record components of variance. The goodness of fit between observed and predicted values has been evaluated using the maximum likelihood approach as in Spudich et al. (1999). Comparing the proposed GMPEs with SP96 and AM05, it is possible to observe a faster decay of predicted ground motion, in particular for distances greater than 25 km and magnitudes higher than 5.0. The result is an improvement in fit of about one order of size for magnitudes spanning from 3.5 to 4.5. [ABSTRACT FROM AUTHOR]

In this paper, waveform similarity analysis is adapted and implemented in a declustering procedure to identify foreshocks and aftershocks, to obtain instrumental catalogues that are cleaned of dependent events and to perform an independent check of the results of traditional declustering techniques. Unlike other traditional declustering methods (i.e. windowing techniques), the application of cross-correlation analysis allows definition of groups of dependent events (multiplets) characterized by similar location, fault mechanism and propagation pattern. In this way the chain of intervening related events is led by the seismogenetic features of earthquakes. Furthermore, a time-selection criterion is used to define time-independent seismic episodes eventually joined (on the basis of waveform similarity) into a single multiplet. The results, obtained applying our procedure to a test data set, show that the declustered catalogue is drawn by the Poisson distribution with a degree of confidence higher than using the Gardner and Knopoff method. The declustered catalogues, applying these two approaches, are similar with respect to the frequency–magnitude distribution and the number of earthquakes. Nevertheless, the application of our approach leads to declustered catalogues properly related to the seismotectonic background and the reology of the investigated area and the success of the procedure is ensured by the independence of the results on estimated location errors of the events collected in the raw catalogue. [ABSTRACT FROM AUTHOR]

In the present work, we develop some local magnitude scales for northwestern Italy based on vertical short-period records. This study is motivated by the possibility of applying the computed scales to an instrumental catalog of more than 25,000 local earthquakes, as this region has been continuously monitored by 12 short-period vertical-component (1C) stations since the mid-1980s. Furthermore, a digital network of three-component (3C) broadband or 5 second sensors has monitored northwestern Italy since 1996. Today, a significant number of earthquakes have been simultaneously recorded by both networks, allowing the calibration of the 1C local scale by using magnitudes computed according to a scale derived for the 3C digital network. Moreover, because station Sant' Anna di Valdieri houses both a 3C (code STV2) and 1C (code STV) sensors, the magnitude scales for the two networks can be developed using the same reference station. The magnitude scale ML = log A + log(R/100) + 0.0054(R - 100) + 3 - S is derived for the 3C digital network with the requirement that the correction S of station STV2 is zero. This scale is based on 10,057 maximum amplitudes (2822 earthquakes) computed from horizontal synthesized Wood-Anderson seismograms, in the hypocentral distance 10 to 310 km and in the range 0 ≤ ML ≤ 5. With respect to an carlier magnitude scale derived for the 3C network constraining the sum of all the station corrections to zero, the magnitudes predicted by the previous equations show an average bias of (-0.2 ± 0.1), which can be ascribed to the different constraint applied to the station corrections. The magnitudes predicted by the scale for the 3C network are used to calibrate magnitude scales based on either total duration or maximum amplitude from synthesized Wood-Anderson seismograms computed for each short-period vertical recording. The magnitude scale obtained considering maximum amplitudes from vertical short-period... [ABSTRACT FROM AUTHOR]

Northwestern Italian weak-motion data were used to study attenuation characteristics of horizontal peak ground acceleration (PGA) and horizontal peak ground velocity (PGV) from earthquakes of local magnitudes (Ml) up to 5.1. Data have been provided by the RSNI (Regional seismic network of Northwestern Italy) and RSLG (Regional seismic network of Lunigiana-Garfagnana) waveform database. The database consists of more than 14 000 horizontal components recorded in the period 1999–2002 by both broadband and enlarged band seismometers. The accuracy of the procedure used to extract PGA values from the velocity recordings was verified comparing observed and derived PGA values at station STV2, which was equipped with both a temporary K2 Kinemetrics accelerometer and Guralp CMG40 broadband sensor. The attenuation of both peak ground acceleration and peak ground velocity was found to be logarithmically distributed with a strong attenuation for low distances (less than 50 km) and low Ml values (<3.0). The resulting equations are: \begin{eqnarray*} {\rm Log(PGA)} & = & - 3.19 + 0.87 M - 0.042 M^2 - 1.92\ {\rm Log}(R) + 0.249S\,,\\[5pt] {\rm Log(PGA)} & = & - 4.23 + 0.76 M - 0.018 M^2 - 1.56\ {\rm Log}(R) + 0.230S\,, \end{eqnarray*} where PGA is expressed in g, PGV is expressed in m/s, M is local magnitude, R is the hypocentral distance in kilometers and S is a dummy variable assuming values of 0 and 1 for rock and soil respectively. For increasing distance and magnitude, both PGA and PGV values show a linear distribution. The validity range of the obtained attenuation relationships is 0–200 km for distances and Ml up to 4.5. Sensitivity studies performed by analysis of residuals, showed that predicted PGA and PGV values are stable with respect to reasonable variations of the model and distances providing the data. Comparisons with attenuation relationships proposed for Italian region, derived from strong motion records, are also presented. [ABSTRACT FROM AUTHOR]

Background: Increased fractional exhaled NO concentrations (FENO) and blood/tissue eosinophilia are frequently reported in allergic children with mild asthma and are thought to reflect the intensity of the inflammation characterising the disease. The aim of this study was to investigate possible differences in FENO levels or in the intensity of the blood eosinophilia in allergic and non-allergic asthmatic children.Methods: 112 children with stable, mild, intermittent asthma with a positive bronchial challenge to methacholine were consecutively enrolled in the study; 56 were skin prick test and RAST negative (non-sensitised) while 56 were sensitised to house dust mites (23 only to house dust mites (monosensitised) and 33 were sensitised to mites and at least another class of allergens (pollens, pet danders, or moulds)). Nineteen sex and age matched healthy children formed a control group.Results: Compared with non-allergic patients, allergic children had a significantly higher rate of blood eosinophilia (p=0.0001) with no differences between mono- and polysensitised individuals. Forced expiratory volume in 1 second (FEV(1)), forced vital capacity (FVC), forced expiratory flow at 25-75% of vital capacity (FEF(25-75%)), and the degree of bronchial reactivity to methacholine were similar in non-atopic and atopic children, with no differences between mono- and polysensitised individuals. FENO levels measured by chemiluminescence analyser were higher in asthmatic children (15.9 (14.3) ppb) than in the control group (7.6 (1.6) ppb, p=0.04) and higher in allergic patients (23.9 (2.1) ppb) than in non-allergic patients (7.9 (0.8) ppb, p=0.0001), but there were no differences between mono- and polysensitised individuals (p>0.1). Significant correlations between blood eosinophilia and FENO levels were seen only in allergic (r=0.35, p<0.01) and in polysensitised individuals (r=0.45, p<0.05).Conclusions: In children with mild asthma, a similar degree of functional disease severity may be associated with a higher inflammatory component in allergic than in non-allergic subjects. [ABSTRACT FROM AUTHOR]

Background: Bronchial hyperresponsiveness and airway inflammation are distinctive features of asthma. Evaluation of nitric oxide (NO) levels in expired air have been proposed as a reliable method for assessing the airway inflammatory events in asthmatic subjects. A study was undertaken to evaluate whether airway hyperresponsiveness is related to levels of exhaled NO.Methods: Thirty two steroid-naive atopic children with mild intermittent asthma of mean (SD) age 11.8 (2.3) years and 28 age matched healthy controls were studied to investigate whether baseline lung function or airway hyperresponsiveness is related to levels of exhaled NO. Airway responsiveness was assessed as the dose of methacholine causing a 20% decrease in forced expiratory volume in one second (FEV(1)) from control (PD(20) methacholine) and exhaled NO levels were measured by chemiluminescence analysis of exhaled air.Results: At baseline asthmatic children had significantly higher NO levels than controls (mean difference 25.87 ppb (95% CI 18.91 to 32.83); p<0.0001) but there were no significant differences in lung function parameters (forced vital capacity (FVC), FEV(1) (% pred), and forced expiratory flows at 25-75% of vital capacity (FEF(25-75%))). In the asthmatic group exhaled NO levels were not significantly correlated with baseline lung function values or PD(20) methacholine.Conclusions: These results suggest that levels of exhaled NO are not accurate predictors of the degree of airway responsiveness to inhaled methacholine in children with mild intermittent asthma. [ABSTRACT FROM AUTHOR]

In this article, H/V ratio are evaluated using different spectral techniques applied to both earthquake and microtremor data (Nakamura technique). In particular, in order to avoid numerical instability, two different numerical techniques are taken into account: (a) a smoothing procedure applied to the spectra of the seismogram components and (b) a regularization method applied to the H/V ratio (Landweber scheme). The data set consists of more than 70 earthquake events recorded by three component sensors displaced in the town of Fabriano (Central Italy) during the Umbria-Marche sequence started on September 1997. The local magnitudes range between 2.7 and 4.4, while the epicentral distances range between nearly 30 and 60 km. The stations were set to continuous recording so that a huge amount of microtremors was stored. The results are compared in terms of predominant frequencies and amplification levels in order to point out the influence of the adopted methods. The H/V ratio provides similar results if applied to a smoothed version of both earthquake and microtremor spectra, confirming that Nakamura technique is a cheap and a fast method to collect information on the site amplification effects. Moreover, the results relevant to earthquake data seem not to depend on the method used to stabilize the H/V ratio, whereas those relevant to microtremor data does. The explanation of this fact is suggested by the behaviour of the Landweber filter showing that the predominant frequency detected by means of microtremor data lies in a high instability region of the spectra. [ABSTRACT FROM AUTHOR]

Investigates the source parameters of the data set of small earthquakes using iterative and constrained deconvolution with empirical Green's functions (EGF) in Italy. Estimation on the relative source time function of the events (RSTF); Use of high-precision relative location to assess the EGF; Determination of the duration of the RSTF.

Objective: To investigate whether during acute asthma episodes a decrease in blood eosinophil count could correlate with the severity of the disease.Design: Prospective study on paediatric asthmatic patients admitted for acute asthma exacerbation between January 1992 and August 1993. All patients were regularly followed up in an outpatient clinic and had had a complete clinical evaluation < 1 month before admission.Setting: Pulmonary division of the G Gaslini paediatric research institute, Genoa, Italy.Subjects: 21 asthmatic patients, 59 (SEM 9) months of age, admitted for acute asthma exacerbation. On the basis of clinical evaluation and the results of blood and microbiological tests performed during acute asthma exacerbations, patients were divided into two subgroups: infected (n = 13) and non-infected (n = 8).Results: All but one of the patients showed a marked decrease in blood eosinophil count during the acute asthma episode, in comparison with recent count (< 1 month before admission) obtained in clinically stable conditions: 662 (116) v 210 (54) eosinophils/mm3, p < 0.0003. The decrease in the eosinophil count was more pronounced in the infected patients than in the non-infected patients, but the difference was not statistically significant (p > 0.05). Similarly, transcutaneous arterial oxygen pressure (PaO2) values measured during acute asthma exacerbations tended to be lower in infected patients, without, however, reaching statistical significance: 8.6 (0.7) v 10.1 (0.9) kPa, p > 0.05). The correlation between the decrease in blood eosinophil count and PaO2 during the acute asthma exacerbations was significant in all the patients (r2 = 0.235, p = 0.022) and in the non-infected patients (r2 = 0.653, p = 0.015), but not in infected patients. In this latter subgroup, a significant negative correlation was found between blood neutrophil counts during acute asthma exacerbations and PaO2 (r2 = 349, p = 0.026).Conclusions: During acute asthma exacerbations in atopic patients without clinical evidence of infection, the decrease in blood eosinophil count correlates significantly with the decrease in PaO2, further supporting the role of eosinophils in allergic asthma. [ABSTRACT FROM AUTHOR]

Abstract: The accuracy of automatic procedures for locating earthquakes is influenced by several factors such as errors in picking seismic phases, network geometry, modeling errors and velocity model uncertainties. The main purpose of this work is to improve the performances of the automatic procedure employed for the “quasi-real-time” location of seismic events in North Western Italy by developing a procedure based on a waveform similarity analysis and by using only one seismic station. To detect “earthquake families” a cross-correlation technique was applied to a data set of seismic waveforms recorded in the period 1985–2002, in a small test area (1600km2) located in the South Western Alps (Italy). Normalized cross-correlation matrices were calculated using about 2700 seismic events, selected on the basis of the signal to noise ratio, manually picked and located by using the Hypoellipse code. The waveform similarity analysis, based on the bridging technique, allowed grouping about 65% of the selected events into 80 earthquake families (multiplets) located inside the area considered. For each earthquake family a master event is selected, manually re-picked and re-located by using Hypoellipse code. Having chosen a reference station (STV) on the basis of the completeness of the available data set, an automatic procedure has been developed with the aim of cross-correlating new seismic recordings (automatically picked) to the waveforms of the events belonging to the detected families. If the new event is proved to belong to a family (on the basis of the cross-correlation values), its hypocenter co-ordinates are defined by the location of the master event of the associated family. The performance of the proposed procedure is tested and demonstrated using a data set of 104 selected earthquakes recorded in the period January 2003–June 2004 and located in the test area. The automatic procedure is able to locate, associating events with the multiplets detected by the waveform similarity analysis, about 50% of the test events, almost independently of the accuracy of the automatic phase picker and without the biasing of the network geometry and of the velocity model uncertainties. [Copyright &y& Elsevier]

The zonation presented in this study has been developed with the aim of applying it as a branch of the logic tree that will be used for the new Italian seismic hazard map, presently in preparation according to the approach of seismotectonic probabilism. With respect to the zonation used for the present official seismic hazard map of Italy, the zonation proposed here considers narrower sources and is based on new and updated seismological data. In particular, some new seismogenic zones are proposed here, introducing areas that were not considered seismogenic until now (e.g., the narrow sources characterised by the presence of transform faults which are almost normal to the trend of the northern Apennines). The preliminary seismic hazard estimates produced with this new zonation aim to identify possible problems that the zonation introduces in the seismicity characterization of the seismogenic zones. As the present seismic hazard assessment was computed by considering a different attenuation model with respect to the one applied for the previous national seismic hazard maps, a re-elaboration of the most recent map referring to Italy has been developed: the comparison of the two maps is a good indicator of the areas where additional seismological investigation is needed to support the zonation presented here. In particular, some zones are not adequately documented with regard to seismicity and a different computation of the seismicity rates is suggested. [ABSTRACT FROM AUTHOR]