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We propose a new fully nonergodic ground motion model for Central Italy, which is one of the most sampled areas in the world after the occurrence of the last seismic sequences of 2009 and 2016–2017. The model predicts 69 ordinates of the Fourier Amplitude Spectrum in the magnitude range 3.2–6.5 and is constrained on a dense set of seismological and geophysical parameters (i.e. stress-drop Δ σ , shear-wave velocity in the uppermost 30 m, VS,30 and high-frequency attenuation parameter at source κ source and site κ 0 ) made available from a non-parametric generalized inversion technique (GIT). The aim of this work is to capture the underlying physics of ground motion related to different source energy levels, as well as to the crustal and geological structure of the region, thus providing less uncertain predictions. Calibration is performed using a stepwise regression approach which has the advantage of taking a more complex functional form (advanced model) when all physical parameters are known while returning a simpler form (base model) when physical data are missing. As a result, the advanced model reproduces the reference rock motion of the region in case the site additional proxies are set to their average values (VS,30 = 1100 m/s, κ 0 =15 ms). We show that the inclusion of the set of physically-based explanatory variables in the regression has a beneficial effect in constraining the uncertainty, leading to a reduction of the high-frequency variability of about 70% on the between-event and 35% on the site-to-site. This reduction can be viewed as the result of the combination of a more effective physical description through the incorporation of the additional proxies and a calibration embedded in a completely nonergodic framework. [ABSTRACT FROM AUTHOR]

This study develops a new spatial correlation model for Italy using the most up-to-date and densest dataset of accelerometer and velocimeter records available. The objective is to estimate the average correlation length and assess its impact on the prediction accuracy of the Italian Shakemap compared to the global model (Loth and Baker, 2013–LB13) adopted in the default configuration of the program. We compute the spatial covariance structure using a geostatistical approach based on traditional variography applied to standardized residuals within the events of a reference ground motion model (ITA10). We observe spatial clusters of the correlation lengths and a wide variability over the Italian territory linked to the profound heterogeneity of the geological and geomorphological context. The obtained estimates are then implemented within the LB13 co-regionalization model in place of the default values while assuming the same cross-correlation coefficients among spectral parameters. Although our results are quite consistent with previous models calibrated for Italy, we find that the inclusion of the new correlation lengths in the Shakemap predictions, assessed through a leave-one-out cross-validation technique, results in a non-appreciable improvement over the global model, thus indicating that the adopted approach is not able to resolve the regional features and the corresponding spatial correlation with reference to individual scenarios. These findings may suggest the need to move towards nonergodic models in the Shakemap computing to better capture the spatial variability or to determine different co-regionalisation matrices more suitable for the regional applications. [ABSTRACT FROM AUTHOR]

This work aims at identifying and modelling statistical dependencies between empirical amplification functions of sites in central Italy and the main geological and geophysical characteristics of the region, within a geostatistical analysis framework. The empirical functions, named δS2S, are estimated by decomposing the residuals of the median predictions of a non-ergodic ground motion model of elastic acceleration response spectra developed for the reference region. To select the model that best describes the spatial variability of the data, the performance of stationary and non-stationary spatial models is compared, the latter being able to constrain the prediction of the empirical functions to physical quantities available in the region and descriptive of the geology, topography and geographical location of the site. Finally, we obtain optimal models of δS2S, for each spectral ordinate, parameterised as a function of geographical coordinates and an input map of shear wave velocity in the upper 30 m (Vs30) constructed ad hoc by combining information gathered from two high-resolution maps available for the region. The methodology allows the development of a new practice-oriented framework for the empirical estimation of site amplification, which can be adopted for the generation of shaking scenarios in the context of regional hazard and seismic risk assessment. • We map the empirical site-to-site response δS2S derived from a nonergodic ground motion model for central Italy. • Predictions of δS2S are obtained by means of a geostatistical approach that allows dealing with spatial non-stationarity. • The best spatial model is obtained as a function of geographic coordinates and Vs30. • Lithologic maps do not show significant improvements in predictions compared with the corresponding stationary models. [ABSTRACT FROM AUTHOR]

This work offers a novel methodological framework to address the problem of generating data-driven earthquake shaking fields at different vibration periods, which are key to support decision making and civil protection planning. We propose to analyse the entire profiles of spectral accelerations and project their information content to unsampled locations in the system, based on the theory of Object Oriented Spatial Statistics. The proposed methodology combines a non-ergodic ground motion model with a fully functional model for the residual term, the latter consisting of (i) the spatially-varying systematic effects due to source, site and path, and (ii) the remaining aleatory error. The proposed methodology allows to generate multiple shaking scenarios conditioned on the data, jointly and consistently for all the vibration periods, overcoming the intrinsic limitations of existing multivariate approaches to the problem. The approach is tested on a vast dataset of ground motion records collected in the study-area of the Po Plain (Northern Italy), for which a region-specific fully non-ergodic GMM was previously calibrated. Our validation tests demonstrate the potentiality of the approach, which is capable to effectively simulate spectral acceleration profiles, while keeping the ability to capture the main physical features of ground motion patterns in the region. [ABSTRACT FROM AUTHOR]

The Engineering Strong-Motion (ESM) flatfile is a parametric table which contains verified and reliable metadata and intensity measures of manually processed waveforms included in the ESM database. The flatfile has been developed within the Seismology Thematic Core Service of EPOS-IP (European Plate Observing System Implementation Phase) and it is disseminated throughout a web portal (http://esm.mi.ingv.it/flatfile-2018/flatfile.php) for research and technical purposes. The adopted criteria for flatfile compilation aim to collect strong motion data and related metadata in a uniform, updated, traceable and quality-checked way to develop Ground Motion Models (GMMs) for Probabilistic Seismic Hazard Assessment (PSHA) and engineering applications. In this paper, we present the characteristics of ESM flatfile in terms of recording, event and station distributions, and we discuss the most relevant features of the Intensity Measures (IMs) of engineering interest included in the table. The dataset for flatfile compilation includes 23,014 recordings from 2179 earthquakes and 2080 stations from Europe and Middle-East. The events are characterized by magnitudes in the range 3.5-8.0 and refer to different tectonics regimes, such as shallow active crustal and subduction zones. Intensity measures include peak and integral parameters and duration of each waveform. The spectral amplitudes of the (5% damping) acceleration and displacement response are provided for 36 periods, in the interval 0.01-10 s, as well as the 103 amplitudes of the Fourier spectrum for the frequency range 0.04-50 Hz. Several statistics are shown with reference to the most significant metadata for GMMs calibrations, such as moment magnitude, focal depth, several distance metrics, style of faulting and parameters for site characterization. Furthermore, we also compare and explain the most relevant differences between the metadata of ESM flatfile with those provided by the previous flatfile derived in RESORCE (Reference Database for Seismic Ground Motion in Europe) project. [ABSTRACT FROM AUTHOR]

The 1915, M w 6.7, Fucino earthquake is one of the most destructive events occurred in the central-southern Apennines (Central Italy) in pre-instrumental era, involving normal faulting in a deep alluvial basin. This study shows the application of the empirical non-ergodic approach (NESK method) for mapping ground shaking related to this historical event, taking into account the regional features of source, propagation and site contributions. Corrections of the source-region and spatially correlated maps of site and path residuals are combined with median prediction at the reference rock (i.e. without site amplification) to generate spatially variable ground shaking and associated variability in terms of peak ground acceleration and spectral ordinates at vibration periods from 0.01s to 2s. The method captures the main spatial non-stationarities and anisotropies of the shaking fields produced by this earthquake in and around the Fucino basin. In particular, we obtain patterns of seismic motion quite in accordance with the results of other methods and the macroseismic intensity field. Marked amplifications of the shaking in the long-periods are also captured, due to the coupling of 3D site effects, especially in the deeper portion of the basin, with propagation effects mainly focused towards the eastern part of the fault. These results confirm that the non-ergodic shaking scenarios from NESK can provide useful indications even in the case of very complex seismological and geological contexts, such as in the case of strong events in deep sedimentary basins. • The shaking scenario of the 1915 Fucino event is reconstructed using a non-ergodic approach. • The empirical method maps effects on shaking due to source, site, and propagation. • Spatial non-stationarities and anisotropies of the shaking field are captured. [ABSTRACT FROM AUTHOR]

This laboratory study deals with a comprehensive investigation of modified concrete specimens using rubber particles obtained from End of Life Tyres (ELT). Different types of mixes have been studied with different percentages of rubber particles used as a partial substitute for natural aggregates by using and comparing mixtures with various types of addition and surface treatment. Three types of rubber particles (ash rubber, crumb rubber and tyre chips) have been employed in the rubberised concrete mixtures replacing partially the natural aggregates. Test results shown that the rubberised concrete mix had some appealing characteristics such as a low mass density but worse compressive strength in line with previous studies. Among the most important findings, a decline in mechanical performance was observed in rubberised concrete specimens at an age of about 60 days. Moreover, cracking and delamination phenomena occurred on the test specimens cured under moist conditions which have never been described in the literature so far. The main innovation is in description of these results regarding time-dependent degradation of rubberised concrete and in a preliminary investigation about the causes of this phenomenon. [ABSTRACT FROM AUTHOR]

Abstract: This paper investigates the optimum design of tuned mass dampers (TMDs) for the seismic protection of inelastic structures. A single linear TMD is treated and is assumed to be applied to a single nonlinear degree of freedom system, described by the Bouc–Wen hysteretic model. The seismic load is modelled by a stationary filtered stochastic process to consider its intrinsic stochastic nature. The optimization problem is set by taking into consideration three different possible objective functions (OFs): the maximum of the peak structural displacement standard deviation, the average hysteretic dissipated energy of a protected building with reference to an unprotected one, and a functional damage that considers the two indexes previously described. Different numerical examples and parametric analysis are shown to confront the three optimization criteria and to determine the best tuning frequency and damping ratio of the TMDs to be used in the structure. Results confirm that the application of a TMD system reduces the amount of the hysteretic dissipated energy, which is a direct measure of damage in the structure, and so it is beneficial for the protection of buildings that develop a nonlinear behaviour under severe dynamic loadings. [Copyright &y& Elsevier]

Abstract: One of the most widely adopted and studied strategies for vibration control both in civil and in mechanical engineering is based on the use of tuned mass dampers (TMD) devices. Many conventional optimization criteria of mechanical parameters have been proposed, based on different approaches typically of a “conventional” type; in other words, they are based on the implicit assumption that all parameters involved are deterministically known. Removing this hypothesis means to convert a conventional optimization into a robust one, so that the solution must be able not only to minimize a performance but also to limit its variation induced by uncertainty in system parameters. In this work, a robust optimal design criterion for a single TMD device is proposed. The analyzed case concerns the structural vibration control of a main system subject to stochastic dynamic loads by a single linear TMD. The dynamic input is represented by a random base acceleration, modelled by a stationary filtered white noise process. It is assumed that not only mechanical parameters regarding main structure and TMD but also input spectral contents are affected by uncertainty. The problem is treated characterizing all uncertain parameters by a nominal mean value and a variance. It is also assumed that all these parameters are statistically independent. The protected main structure covariance displacement (dimensionless by dividing for the unprotected one) is adopted as the deterministic objective function (OF). Its mean and standard deviation are evaluated to perform the robust design. Robustness is formulated as a multiobjective optimization problem, in which both the mean and the standard deviations of the deterministic OF are minimized. Comparisons with a conventional approach based on the same OF show that the robust approach induces a significant improvement in performance stability. [Copyright &y& Elsevier]

Abstract: In this paper, a parametric stochastic analysis of isolated bridge is proposed with the aim to assess isolation performance and to investigate effects of energetic influence on protection efficiency. The analysis has been carried out in terms of two stochastic parameters of pear-deck maximum displacement and hysteretic energy response, of which a qualitative trend has been observed. Isolated bridge is described by a simple two degree of freedom (TDoF) Bouc–Wen hysteretic model, which has been introduced for its intrinsic ability in reproducing a wide range of real devices behavior. With the aim of taking into consideration intrinsic stochastic nature of seismic events, the ground motion and the structural response have been described by random vibration approach. Results obtained show that protection achieved by shifting structural natural period and reducing input energy by devices dissipation have counteracting effects if related to deck lateral displacement. [Copyright &y& Elsevier]

Motivated by the crucial implications of Ground Motion Models in terms of seismic hazard analysis and civil protection planning, this work extends a scalar Ground Motion Model for Italy to the framework of Functional Data Analysis. The inherent characteristic of seismic data to be incomplete over the observation domain of oscillation periods entails embedding the analysis in the context of partially observed functional data and performing data reconstruction. This work proposes a novel methodology that accounts for the fact that parts of the curves are directly observed and other parts are reconstructed, thus, characterized by greater uncertainty. The method defines observation-specific functional weights, which enter the estimation process to reduce the impact that the less reliable portions of the curves have on the final estimates. The classical methods of smoothing and concurrent functional regression are extended to include weights. The advantages of the proposed methodology are assessed on synthetic data. Eventually, the weighted functional analysis performed on seismological data is shown to provide a natural smoothing and stabilization of the spectral estimates of the Ground Motion Model considered. for this article are available online. [ABSTRACT FROM AUTHOR]

Rupture directivity and its potential frequency dependence is an open issue within the seismological community, especially for small‐to‐moderate events. Here, we provide a statistical overview based on empirical evidence of seismological observations, thanks to the large amount of high‐quality seismic recordings (more than 30,000 waveforms) from Central Italy, which represents an excellent and almost unique natural laboratory of normal faulting earthquakes in the magnitude range between 3.4 and 6.5 within the time frame 2008–2018. In order to detect an anisotropic distribution of ground motion amplitudes due to the rupture directivity, we fit the smoothed Fourier Amplitude Spectra (FAS) cleared of source‐, site‐ and path‐effects. According to our criteria, about 36% of the analyzed events (162 out of 456) are directive and the distribution of rupture direction is aligned with the strikes of the major faults of the Central Apennines. We find that the directivity is a band‐limited phenomenon whose width may extend up to five times the corner frequency. The results of this research provide useful insights to parameterize directivity, to be explicitly implemented in future ground motion modeling and scenario predictions. Plain Language Summary: In seismology, directivity is one of the source phenomena that causes large spatial variability of earthquake ground motions and is related to the features of the rupture propagation along the fault. The importance of this effect is very well known for large‐magnitude events (M > 6), while it is still an open issue for small‐to‐moderate events. The aim of this paper is to recognize directive events and quantify their strength in Central Italy, using a large data set of earthquakes in the magnitude range 3.4–6.5 that occurred between 2008 and 2018. We find that about 36% of the analyzed events are directive, caused by rupture propagations oriented along the NW‐SE alignment of the Central Apennines fault systems. Furthermore, we find that directivity is a band‐limited phenomenon and that as the directivity gets stronger, the frequency band becomes wider. Our contribution provides a useful insight with the possibility to improve the parametrization of directivity within the empirical seismic hazard assessment. Key Points: Statistical procedure to detect directivity effects in small‐to‐moderate earthquakes analyzing the aleatory residuals of the ground motionThe directive events are the 36% of the data set and the distribution of rupture direction is aligned with the strikes of the faults systemThe observed directivity is a frequency‐dependent band‐limited phenomenon, which can occur up to five times the value of corner frequency [ABSTRACT FROM AUTHOR]

This work introduces a new Ground Motion Model (GMM) to predict the horizontal and vertical components of PGA, PGV and acceleration response spectra up to 5s for the volcanic events in Italy. The model updates the GMM for the horizontal components, recently developed by Lanzano & Luzi [1], and shows relevant amplitudes in near-source and a frequency content richer in intermediate-to-low frequencies. The comparison with an event not used for the calibration and belonging to another volcanic district in Italy is promising for the extension of the model to other areas. Finally, we present a case study of a site, in the proximity of Mount Etna in eastern Sicily region, which allows us to evaluate the impact of these models in the framework of a Probabilistic Seismic Hazard Analysis (PSHA). • a ground motion model for the vertical component of volcanic earthquakes in Italy is proposed. • The ground motion can be high in near-source conditions for shallower events. • The shallow volcanic events attenuates with distance rapidly than the active crustal ones. • The peak frequency content of volcanic events is shifted to lower frequencies. • a PSHA case study is discussed with focus on the impact of the use of the GMM proposed in the paper. [ABSTRACT FROM AUTHOR]

The characterization of the fling-step represents a challenging task due to the shortage of near-source records with permanent tectonic displacement and the limitation in retrieving the fling-amplitude from accelerometric waveforms. In recent years, innovative ground-motion processing techniques have been developed for a more accurate estimation of both fling-displacements and spectral displacements in contrast to traditional bandpass filtering, although their application is still unusual. In this paper, we exploit the newly released dataset of the Near-Source Strong-motion records (NESS2) uniformly processed with the extended BASeline COrrection technique (eBASCO), against which we propose: (1) a new empirically-based ground motion model (GMM) for the prediction of the fling-step, and (2) an adjustment factor of the spectral displacements predicted by a reference GMM to account for the contribution of the fling-step at long periods. Such models are in agreement with observations and existing GMMs, and thus could be advantageously employed in seismic hazard analyses. • A new model for fling is calibrated on the dataset of near-source records (NESS2). • We propose a corrective function of displacement spectra to account for fling-effect. • The calibration dataset is uniformly processed with a baseline correction technique. [ABSTRACT FROM AUTHOR]

Abstract: The primary objective of the present study is to explore a new definition of seismic response spectrum, where the uncertainty, that strongly affects the system and excitation parameters, is treated by fuzzy random theory. The proposed work is based on a simultaneous probabilistic and credibilistic representation of uncertainty used in a specific variety generally known as fuzzy probabilistic approach. The standard stochastic approaches normally consider the ground acceleration as the only source of uncertainty modeled as a stochastic process with deterministic structural parameters. But, in reality the parameters of the ground acceleration have a fuzzy credibilistic nature. In the present study, a methodology is proposed to describe the ground motion model that considers the credibilistic nature of the parameters involved. At the same time, the structural parameters are also considered to be fuzzy type, in order to take into account properly the level of approximation that affects their determinations. Thereby, a fuzzy version of the classical stochastic response spectrum evaluation of linear systems is obtained. The consistency of fuzzy stochastic response spectrum obtained by the proposed approach is studied with respect to available non-probabilistic formulations reported in the literature. [ABSTRACT FROM AUTHOR]

Tuned mass dampers (TMD) are well known as one of the most widely adopted devices in vibration control passive strategies. In the past few decades, many methods have been developed to find the optimal parameters of a TMD installed on a structure and subjected to a random base excitation process, but most of them are usually based on an implicit assumption that all of the structural parameters are deterministic. However, in many real cases this simplification is unacceptable, so robust optimal design criteria becomes a viable alternative to better support engineers in the design process. In Robust Design Optimization (RDO) approaches, indeed the solution must be able to not only minimize the performance but also to limit its variation induced by uncertainty. Most of the currently available RDO methods are based on a probabilistic description of the model uncertainty, even if in many cases they are not able to explicitly include the influence of all the possible sources of uncertainties. Therefore, in this study, a fuzzy version of the robust TMD design optimization problem is proposed. The consistency of the fuzzy approach is studied with respect to the available non-probabilistic formulations reported in the literature and an application to an example of a robust design of a linear TMD subjected to base random vibrations in the presence of fuzzy uncertainties. The results show that the proposed fuzzy-based approach is able to give a set of optimal solutions both in terms of structural efficiency and sensitivity to mechanical and environmental uncertainties. [ABSTRACT FROM AUTHOR]

Steel bars pitting corrosion is a process that strongly jeopardises the reliability of the reinforced concrete structures exposed to chlorides. The proper treatment of uncertainties that affects geometrical, mechanical and chemical involved parameters is for some aspects still an open question because the probabilstic approach, ordinarily adopted, presents some limitations not only when few data are available to characterise involved variables but especially when some parameters are ambiguously defined, not only in terms of distribution type. In these circumstances a possibilistic approach could respresent a reasonable alternative to perform this specific reliability analysis. In the present study, the problem parameters are modelled by using a complete fuzzy criterion and a time-dependent fuzzy safety factor is defined in order to evaluate how the residual flexural resistance is greater or less than the bending moment. Moreover, the study provides a more proper mathematical analysis of the chloride penetration into concrete. [ABSTRACT FROM AUTHOR]

Abstract: This paper is focused on the comparison between different approaches in structural optimization. More precisely, the conventional deterministic optimum design, based on the assumption that the only source of uncertainty concerns the forcing input, is compared to robust single-objective and multi-objective optimum design methods. The analysis is developed by considering as case of study a single-degree-of-freedom system with uncertain parameters, subject to random vibrations and equipped with a tuned mass damper device (TMD). The optimization problem concerns the selection of TMD mechanical characteristics able to enlarge the efficiency of the strategy of vibration reduction. Results demonstrate the importance of performing a robust optimum design and show that the multi-objective robust design methodology provides a significant improvement in performance stability, giving a better control of the design solution choice. [Copyright &y& Elsevier]

In this paper we present the ground response analyses (GRA) of a site where an industrial facility is planned. Due to its location on an active normal fault system known as a relevant seismic gap, the Mt. Morrone Fault system (MMF), and at the edge of a basin filled with slow velocity continental deposits, a inter-disciplinary and non-standard approach has been applied to assess the seismic input of the dynamic numerical analyses. It includes geological, seismological, geotechnical and engineering contributions. Two fault scenarios, MMF1 and MMF2, were considered and scenario-based (SSHA) and probabilistic (time-dependent, TD, and time-independent, TI) seismic hazard (PSHA) analyses were implemented. Comparison among the spectra corresponding to the 90th percentile of the SSHA statistical distribution and the PSHA average ones shows that the SSHA MMF2 has values similar to the PSHA TD model. The SSHA 90th percentile distribution was selected as target spectra to retrieve the seismic input for GRA. Nonlinear numerical simulations of seismic wave propagation were implemented to derive surface ground motion parameters. GRA acceleration response spectra and their PGA are notably higher, and thus on the side of safety, than those obtained following the Italian code approach for seismic resistant buildings. These results confirm that a scenario-based methodology can better capture the shaking effect in near-field conditions, avoiding possibly unconservative underestimations of the seismic actions and in view of a more robust performance-based approach used by engineers for either new design and/or assessment/retrofit purposes of the built environment. • A site-specific surface ground motion analyses of a near-fault industrial site using a interdisciplinary methodology. • Similarity of response spectra for deterministic scenario-based and probabilistic time dependent seismic hazard analyses at the bedrock. • The seismic input at the bedrock from the fault scenarios, is more severe than the values predicted by the seismic resistant code for a rock site. • A fully nonlinear modeling is more appropriate than an equivalent linear one due to the high strain level induced by the scenario seismic input. [ABSTRACT FROM AUTHOR]

The main objective of this work is to provide two zonations of Italy useful to incorporate regional source and path effects in empirical Ground Motion Models (GMMs). To this end, we revise existing zonations developed for seismic and tsunami hazard studies, based on the results of a residual analysis between the observations of the ITACAext dataset and the predictions of ITA18, a GMM recently developed for Italy. The analysis consists in the decomposition of the residuals into repeatable terms, according to the well-established approach used for the calibration of non-ergodic models. Based on the spatial trend of the interpolated residuals, and geological and seismological considerations, the zonations are proposed and discussed, in the perspective of supporting regionalization of a future generation of GMMs for Italy. • The goal is to provide the tools to regionalize seismic motion in Italy. • Zonation for source effects is based on spatial variability of the event residuals. • Zonation for propagation effects is based on spatial variability of random residuals. [ABSTRACT FROM AUTHOR]