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DInSAR data provide a powerful tool to recognize the Earth's surface where permanent deformations are concentrated and undergo the strongest ground motion during an earthquake, i.e., defining the epicentral area. We analyzed three recent seismic events in the Apennines belt in Italy related to extensional and contractional earthquakes and documented that the largest macroseismic intensity is recorded where the ground underwent the largest vertical component of motion and the stronger vertical component of the peak ground acceleration. Besides site amplification effects that may occur everywhere even outside the epicentral area, we infer that the vertical oscillations in the so-called near-field allow the horizontal shaking to be more effective, hence producing larger damage above the active crustal volume. The active volume is the one moving vertically and is contemporaneously crossed by seismic waves nucleated by the shear on the fault. The surrounding passive volume in the far field is only crossed by seismic waves. The near field areas are elliptical and cover areas of 300–600 km2 for a range of M w 6–6.9, and they should be the areas where the highest seismic hazard must be expected. Therefore, their area is too large to be neglected for seismic hazard assessment. • Coseismic vertical deformation is recorded for three Apenninic seismic sequences. • Vertical deformation coincides with the largest shaking recorded (PGA). • Maximum vertical DInSar data delimit the highest macroseismic and intensity measures. • The largest damage is recorded in the so-called active crustal volume. • The active volume is where vertical displacement occurs while crossed by seismic waves. [ABSTRACT FROM AUTHOR]

Abstract: The influence of underground cavities in assessing local seismic response was studied in some test sites in the urban area of Catania. The investigations were performed both in a natural cavity and in artificial tunnels, taking into account the near-surface geological features. Earthquake and ambient noise records were processed through spectral ratio techniques, investigating also on the possible directional effects. A set of 70 local and regional earthquakes was recorded by seismic stations deployed nearby a grotto located in the northern part of the town as well as in a reference site on the bedrock. As regards ambient noise measurements, about 30 recording sites were selected, locating the mobile stations inside the cavities as well as along short profiles crossing them. Spectral ratios coming out from performed measurements show that spectral peaks in the frequency range 3.0–7.0 Hz appear stable nearby the cavity, and show a tendency to be less pronounced at increasing distance from it. Moreover, the natural period of buildings erected nearby and over the considered cavity was evaluated to investigate on possible soil-structure interactions. The results so far obtained point out that the height of the cavities plays an important role. It appears evident that only cavities having height greater than about 4m show significant H/V amplification peaks. Moreover, spectral ratios deriving from measurements performed inside the cavities show less pronounced spectral peaks than those obtained from measurements over and outside the cavities. Investigations about the interaction with nearby edifices show slight increments in the amplitude of spectral peaks representing the fundamental period of buildings located over the investigated grotto. Finally, our observations set into evidence a tendency toward a pronounced polarization of the ground motion that is parallel to the main axis of the grotto. [Copyright &y& Elsevier]

Abstract: The influence of site effects on landslide triggering during earthquakes has been inferred in several studies, but its evaluation is made difficult by the complexity of factors controlling the dynamic response of potentially unstable slopes and also by the lack of local ground motion instrumental observations. This work explores this problem and reports new findings based on an ongoing long term accelerometric monitoring conducted on a landslide-prone test area in the Apennine Mountains, Italy, where the presence of site effects enhancing seismic susceptibility of local slopes has been invoked on the basis of historic accounts of landsliding triggered at large epicentral distance. The recordings relative to low-to-moderate magnitude earthquakes showed significant amplifications affecting hillslope portions covered by thick (>5m) colluvia and pronounced amplification maxima oriented along the local maximum slope direction on a recent deep-seated landslide. While the amplifications seem most likely linked to high impedance contrast between surface materials and underlying substratum, the causes of directivity are less clear. The case of the monitored test site together with evidence of site response directivity identified on other hillslopes, suggest that the directivity phenomena can result from a combination of topographic, lithological and structural factors that act together to re-distribute shaking energy, focusing it on site-specific directions. Thus, it is difficult to single out the critical factors controlling such phenomena and no general criterion for the identification of sites affected by directivity is proposed here. Nevertheless, the presence and orientation of site response directivity can be revealed through reconnaissance techniques by using recordings of seismic weak motion and/or ambient microtremors, and calculating azimuthal variation of shaking energy and horizontal-to-vertical ground motion spectral ratios. A comparison with the recordings obtained during the recent MW =6.3 earthquake that hit the Abruzzo region in April 2009 demonstrated that analysis relying on data from low energy events can furnish valid indications for slope behaviour also under stronger shaking, provided the data are well differentiated in terms of distance, azimuth and source characteristics. Furthermore, the comparative analysis of the Abruzzo earthquake recordings at a landslide and reference sites showed that directivity properties of strong shaking had been correctly anticipated using earlier weak motion observations. However, under the complex slope conditions the identification of resonance frequencies from horizontal-to-vertical spectral ratios estimated from weak-motion accelerometric recordings does not seem reliable, and better results have been obtained by velocimetric microtremor recordings. [Copyright &y& Elsevier]

Prediction of surface ground motion based on advanced approaches is a non-trivial task at large area. In fact, advanced approaches require a detailed geological and geotechnical subsoil model based on geological, physical and mechanical properties retrieved from in situ investigations and laboratory data, and to perform time consuming numerical simulation of the seismic site response. Bearing in mind that there is a lack of available site investigations and laboratory data at large area, simplified methods based on "soft data" are often adopted. On this regard, a methodology to perform seismic site response analyses at national scale is proposed in this paper, based on the following assumptions: 1) homogeneous areas were identified at national scale based both on morpho-geological and lithological properties, in order to classify and analyse site-data archived in the Italian database of seismic microzonation studies; 2) geotechnical subsoil one-dimensional models of the Italian site conditions were defined according to site-data; 3) in accordance with the reference seismic hazard levels, pseudo-acceleration response spectra were selected as input motions for numerical simulations. About thirty million numerical simulations of seismic site response were performed, and national maps of seismic shaking amplification factors were produced in terms of ratio of response spectra referred to three intervals of period. This estimation of surface ground motion based on the proposed procedure is a supporting tool for large area territorial and emergency planning. • Numerical models of national site conditions were identified from Italian database. • Numerical models were extended down to the seismic bedrock. • Morpho-geological clusters were used to spatialize input and output data. • National maps of amplified seismic intensity were proposed. • The proposed procedure will support seismic risk mitigation at large area. [ABSTRACT FROM AUTHOR]

Many existing earth dams have been designed and built worldwide before the establishment of a seismic code, so that it is of relevant interest to evaluate their seismic performance and post-seismic operational conditions. This requires an accurate geotechnical characterisation of the dam and foundation soils, a proper definition of the seismic scenarios at the site of the dam, the use of simplified procedures for screening-level seismic analyses and advanced non-linear dynamic analyses to study the most critical seismic scenarios. This process has been used for the evaluation of the seismic performance of a zoned earth dam located in a high seismic hazard area of Southern Italy. In this paper the available data of historical seismicity at the site of the dam and the results of a probabilistic seismic hazard analysis are first discussed and input ground motions are selected using compatibility criteria with the energy and frequency content of the expected target motion in a range of vibration period relevant for the non-linear response of the dam. Seismic performance of the dam is then evaluated through procedures based on Newmark-type computations, in which permanent displacements are related to ground motion characteristics and to the seismic resistance of the dam, the latter evaluated detecting the earthquake-induced plastic mechanisms and the corresponding critical accelerations. Also, an original improvement of the well-known Makdisi & Seed procedure, was proposed to better capture the actual influence of non-linear soil behaviour in the evaluation of horizontal acceleration and permanent displacements of the crest of the dam. The analysis results pointed out the relevant role of the earthquake-induced shear strength reduction on the dam permanent displacements. • The seismic performance of an earth dam is evaluated through displacement analyses. • A finite difference model was calibrated using laboratory and field data. • Input motions were defined through historical and probabilistic hazard analysis. • Permanent displacements were estimated using well-known and an original procedure. • The role of shear strength reduction occurring in the dam materials is highlighted. [ABSTRACT FROM AUTHOR]

In this study, we derive a large-scale V s30 map for Italy starting from the global terrain geomorphological classification based on normalized slope, local convexity, and surface texture (after Iwahashi et al., 2018). The novelty of the present work is the integration of a large amount of data from the Italian seismic microzonation dataset, consisting in about 35,000 borehole logs and 11,300 Vs profiles. The results of our analysis suggest that the geomorphological classes are correlated to subsoil lithologies and V s30 values more than surface lithological types (after Amanti et al., 2008). As already done in Japan (Matsuoka and Wakamatsu, 2006), Greece (Stewart et al., 2014), Central and Eastern North America (Parker et al., 2017), and Pacific Northwest Region of North America (Ahdi et al., 2017), we found a proxy dependence of V s30 from slope gradient and elevation through a lognormal linear regression model for each geomorphological class. A stepwise method allowed us to give meaning and statistical robustness to the regression model dependencies. The polygons inconsistent with the Iwahashi et al. (2018) approach (e.g., Meso-Cenozoic carbonate units of Apulian block and Hyblean Plateau related to the foreland domain) were replaced with the polygons of the lithological map (Amanti et al., 2008) and the associated V s30 lognormal average values. Therefore, a hybrid raster V s30 map was created with a spatial resolution of 50 × 50 m. The comparison with other previous maps shows how the forecast improves in terms of both accuracy and precision. For these reasons, the new V s30 proxy-based map for Italy based on the seismic microzonation dataset represents a useful tool for improving several applications: ShakeMaps, stochastic event based hazard map, total hazard map, assessment of coseismic instabilities, seismic risk assessment for spatially distributed emergency and resilience systems. V s30 raster maps and supplementary material are available in the Research Data (doi: 10.17632/8458tgzc73.1). • Vs30 Italy map was created starting from the global geomorphological classification. • Seismic microzonation dataset was used for better estimation of Vs30 for Italy. • Geomorphological classes represent the best strategy for Vs30 large scale mapping. • The new Vs30 map is a useful tool for seismic risk assessment at large scale. [ABSTRACT FROM AUTHOR]

The emergency management system is a complex network consisting of structural components, such as buildings, infrastructure and emergency areas, and non-structural elements, such as procedures, emergency workers, information management, etc. This document describes the evaluation of only its structural components. The system was adopted at the territorial scale and is defined by a multi-municipality area extension. This paper presents a methodology for the probabilistic evaluation of operating the emergency structural system in the case of a seismic event occurrence and, in detail, it highlights the methodology for calculating the seismic hazard including seismic local effects (amplification and permanent co-seismic effects). Systemic seismic risk and associated impact were considered in a rigorous and unified way. Moreover, the importance of the interconnection and interdependence between elements at risk belonging to the same system and between different networks at urban or territorial scales is well known. The aim of the proposed methodology is to evaluate the operational losses of an emergency system considering the connections between the components of the system, contributing, in an original way, to the estimation of the seismic effects. The fundamental characteristics of this calculation are: • Estimating ground motion amplification at the territorial scale using a Vs30 from a probabilistic map obtained with the seismic microzonation national database; • Estimating shaking scenarios in terms of PGA and PGV depending on the Vs30; • Co-seismic permanent failure and deformations (landslide and liquefaction) evaluated with regression logistic methods. Finally, a case study is presented showing the application of the methodology on a real emergency system in an area of southern Italy. Stochastic evaluation of structural emergency system of a Territorial Context (TCSO index). Stochastic evaluation of seismic hazard with spatial correlation ground motion fields. Probabilistic Vs30 map from Seismic Microzonation Databe (DBMS). Coseismic effects for landslide and liquefaction triggered for any realization of stochastic base hazard. [ABSTRACT FROM AUTHOR]

Total seismic hazard assessment (i.e. the base hazard modified by local site conditions) plays a key role in seismic risk prevention and mitigation. This is an important topic due to the impact of a reliable hazard assessment on the resilience of local communities in the case of an earthquake. This paper presents a study that evaluates the total seismic hazard for the entire Italy (excluding the Island of Sardinia). The results are expressed in terms of amplification factors and total hazard parameters. To this end, soil characterisation was performed, firstly using Italian Seismic Network data for 259 sites uniformly distributed across Italy, and secondly using the mean value of the shear wave velocity, available from a global dataset produced by the United States Geological Survey. The amplification effects were quantified according to i) an approach consistent with the Italian Building Code; and ii) one-dimensional site response analyses. These two procedures are referred to as "parsimonious" and "rigorous" here, respectively. The results indicate a generally satisfactory match between the estimates obtained by means of these two procedures for periods lower than 0.5 s, while parsimonious procedures at periods longer than 0.5 s provide an upper limit on the total seismic hazard. Finally, a seismic classification in terms of the classes of total hazard parameters is proposed for the Italian peninsula area. • Prediction of shear wave velocity was cross-checked against data from Italian sites; • The total seismic hazard was satisfactory estimated based on "poor" data; • Basic procedures can be used for a precautionary estimate of total seismic hazard; • National maps of the total seismic hazard were proposed; • Total seismic hazard maps can support urban planning and seismic risk mitigation. [ABSTRACT FROM AUTHOR]

This study presents a first attempt to couple two of the most important components of seismic risk mitigation strategies: probabilistic seismic hazard analysis (PSHA) and seismic microzonation. We show an application in the westernmost sector of the Liguria region in northwestern Italy, an area where strong earthquakes (up to about magnitude 6.5) occurred in the past producing hundreds of casualties. The final goal is to produce probabilistic seismic hazard maps for peak ground acceleration and spectral acceleration that incorporate site amplification (by amending existing ground motion attenuation models for rock conditions with an additional amplification term provided by microzonation studies) on a municipal scale. To this end, a partially non-ergodic approach is applied according to modern practice. Compared to conventional, ergodic hazard assessments for rock conditions and flat topography, such maps provide at a glance a finer picture of the actual hazard of the area under study, highlighting those sites where the ground motion hazard is dominated by local amplification effects. At these sites, the expected ground motions are up to twice the values resulting from the traditional, ergodic PSHA on rock. Besides hazard maps, results are also presented in terms of uniform hazard spectra for a number of target sites. Comparison with the isoseismal maps of past earthquakes have revealed a good agreement between the spatial distribution of the assessed hazard and that of felt intensities, with greater damage observed in areas presenting significant amplification effects and, consequently, a higher seismic hazard. • We analyze the role of local geology on seismic hazard. • Site effects from seismic microzonation maps are incorporated into PSHA in a robust, fully probabilistic way. • Partially non ergodic, site-specific probabilistic seismic hazard maps are defined. • Site-specific hazard is up to twice the traditional, ergodic hazard on rock. • The hazard distribution agrees well with the damage distribution associated with past earthquakes. [ABSTRACT FROM AUTHOR]