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Mining wastewater (MWW) can contain mercury in high concentrations. In this study, four autochthonous aquatic plant species (Eichhornia Crassipes—EC, Marsilea Quadrifolia—MQ, Ludwigia Helminthorrhiza—LH, and Lemna Minor—LM) were identified and tested for phytoaccumulation of total mercury (THg). To better study the accumulation phenomenon and macrophyte responses, this work has been divided into three phases, and pilot-scale reactors have been used to simulate real conditions. The results highlighted that, in case of 15 µgTHg,fed, the bioconcentration factor (BCF) was significantly higher in EC (19.04) and LH (18.41) with respect to MQ and LM (almost six times and two times higher, respectively). EC granted the best results in terms of THg accumulation (50.90%) and lower evapotranspiration of THg phenomenon with respect to LH. A significant decrease of the BCF (from 23.45 to 21.98) and an increase of the TF (from 0.23 up to 0.73) after 42 d highlighted that a breaking-time in terms of THg accumulation was reached due to the deterioration of the roots. In terms of the kinetics of THg removal by bioaccumulation, an HLT of 69.31 d was found, which is more than the breaking-time of the EC system, proving that a periodic replacement of exhausted macrophytes is required to obtain a higher percentage of THg removal.

Kosovo is one of the most seismically active regions in Europe, lying within the Alpine-Mediterranean tectonic belt. Historical records for the region show several catastrophic earthquakes with epicentral intensity IX (MCS). However, due to Kosovo’s high population density, high prevalence of traditional construction, and insufficient enforcement of building codes, Kosovo is vulnerable to earthquake damage. In this study, we present earthquake hazard maps for bedrock conditions in Kosovo based on the well-known Neo-deterministic Seismic Hazard Assessment (NDSHA) method. NDSHA relies upon the fundamental physics of wave generation and propagation in complex geologic structures to generate realistic time series, used as input for the computation of several ground motion parameters, integrating the available knowledge of seismic history, seismogenic zones and morphostructural nodes. In accordance with continuum mechanics, the tensor nature of earthquake ground motion is preserved, producing realistic signals using structural models obtained by tomographic inversion and earthquake source information readily available in literature. Our maps are generally consistent with the observed intensity IX (MCS) and suggest that, in some instances, intensity X could be reached.

The regional seismic hazard in Pakistan and adjoining regions is assessed using the Neo-deterministic seismic hazard assessment approach (NDSHA). Synthetic seismograms are generated by the modal summation technique at the nodes of a grid that covers the studied area. The main input for the computations consists of a set of earthquake sources and of the structural model where the seismic waves propagate. The earthquake sources are parameterised within the active seismogenic areas by defining the focal mechanism, the depth and the magnitude, obtained through the analysis and re- elaboration of the past seismicity. The peak displacement (Dmax), peak velocity (Vmax) and design ground acceleration (DGA) are then extracted from the synthetic signals and plotted on the 0.2° x 0.2° grid to construct the seismic hazard map of the studied area. There are few probabilistic hazard maps available for Pakistan, however, this is the first study aimed at producing a neo-deterministic seismic hazard map for Pakistan and adjoining regions.The most severe hazard is found in the epicentral zone of the great Muzaffarabad earthquakes of 2005 and its surroundings, where the DGA estimate falls in the highest range 0.60 g – 1.2 g. The peak velocity and displacement in the same region are estimated as 60−120 cm s−1 and 30−60 cm, respectively.

The procedure we developed, and applied to a few relevant cases, leads to the seismic verification of a building by: a) use of a scenario based neodeterministic approach (NDSHA) for the calculation of the seismic input, and b) control of the numerical modeling of an existing building, using free vibration measurements of the real structure. The key point of this approach is the strict collaboration, from the seismic input definition to the monitoring of the response of the building in the calculation phase, of the seismologist and the civil engineer. The vibrometry study allows the engineer to adjust the computational model in the direction suggested by the experimental result of a physical measurement. Once the model has been calibrated by vibrometric analysis, one can select in the design spectrum the proper range of periods of interest for the structure. Then, the realistic values of spectral acceleration, which include the appropriate amplification obtained through the modeling of a “scenario” input to be applied to the final model, can be selected. Generally, but not necessarily, the “scenario” spectra lead to higher accelerations than those deduced by taking the spectra from the national codes (i.e. NTC 2008, for Italy). The task of the verifier engineer is to act so that the solution of the verification is conservative and realistic. We show some examples of the application of the procedure to some relevant (e.g. schools) buildings of the Trieste Province. The adoption of the scenario input has given in most of the cases an increase of critical elements that have to be taken into account in the design of reinforcements. However, the higher cost associated with the increase of elements to reinforce is reasonable, especially considering the important reduction of the risk level.

Lessons learnt from the destructive earthquakes occurred during the new millennium provide new opportunities to take action, revise and improve the procedure for seismic hazard assessment. When dealing with cultural heritage and critical structures (e.g. nuclear power plants), where it is necessary to consider extremely long time intervals, the standard hazard estimates are by far unsuitable, due to their basic heuristic limitations. A viable alternative to traditional seismic hazard assessment is represented by the use of the scenario earthquakes, characterized at least in terms of magnitude, distance and faulting style, and by the treatment of complex source processes. The scenario-based methods (NDSHA) for seismic hazard analysis, where realistic and duly validated synthetic time series, accounting for source, propagation and site effects, are used to construct earthquake scenarios. The NDSHA procedure provides strong ground motion parameters based on the seismic waves propagation modeling at different scales accounting for a wide set of possible seismic sources and for the available information about structural models. Actually, the proposed method can be applied at regional (national) scale, computing seismograms at the nodes of a grid with the desired spacing, also integrated with time dependent scenarios, or at local (metropolitan) scale, taking into account detailed source characteristics, the path and local geological and geotechnical conditions by means of 3D laterally heterogeneous anelastic models. The relevance of the realistic modeling, which permits the generalization of empirical observations by means of physically sound theoretical considerations, is evident, as it allows for the optimization of the structural design with respect to the site of interest.

Lessons learnt from the destructive earthquakes occurred during the new millennium provide new opportunities to take action, revise, and improve the procedure for seismic hazard assessment (SHA). A single hazard map cannot meet the requirements from different end-users; the mapping of the expected earthquake ground motion that accounts for events’ recurrence may be suitable for insurances. When dealing with cultural heritage and critical structures (e.g., nuclear power plants), where it is necessary to consider extremely long time intervals, the standard hazard estimates are by far unsuitable, due to their basic heuristic limitations. While time-dependent SHA may be suitable to increase earthquake preparedness, by planning adequate mitigation actions, for critical structures (i.e., those for which the consequences of failure are intolerable) the maximum possible seismic input is relevant. Therefore the need for an appropriate estimate of the seismic hazard, aimed not only at the seismic classification of the national territory, but also at the capability of properly accounting for the local ampli␣cations of ground shaking, as well as for the fault properties, is a pressing concern for seismic engineers. A viable alternative to traditional SHA is represented by the use of the scenario earthquakes, characterized at least in terms of magnitude, distance, and faulting style, and by the treatment of complex source processes. The relevance of the realistic modeling, which permits the generalization of empirical observations by means of physically sound theoretical considerations, is evident, as it allows the optimization of the structural design with respect to the site of interest. The time information associated with the scenarios of ground motion, given by the intermediate-term middle-range earthquake predictions, can be useful to public authorities in assigning priorities for timely mitigation actions. Therefore, the approach we have developed naturally supplies realistic time series of ground motion useful to preserve urban settings, historical monuments, and relevant man-made structures.

Neo-deterministic seismic hazard assessment. Operational issues are a pressing concern in seismic hazard assessment (SHA), as fatally evidenced by the most destructive recent events worldwide, including the Tohoku (2011) and Haiti (2010) earthquakes (Wyss et al., 2012). A reliable and comprehensive characterization of expected seismic ground shaking, eventually including the related time information, is essential in order to develop effective mitigation strategies and to increase earthquake preparedness (Peresan et al., 2012). Nowadays it is well recognized by the engineering community that standard hazard indicator estimates (e.g. seismic PGA) alone are not sufficient for the adequate design, mainly for special buildings and infrastructures (Field et al., 2000; Zuccolo et al., 2008). Moreover, any effective tool for SHA must demonstrate its capability in anticipating the ground shaking related with large earthquake occurrences, a result that can be attained only through rigorous verification and validation process (Stein et al., 2011, 2012; Peresan and Panza, 2012).

The Greater Tehran area is the most important city of Iran and hosts about 20% of the country population. Despite the presence of major faults and the occurrence of historical earthquakes, nowadays the seismicity is relatively quite low and this enhances the use of simulation methods for microzonation and seismic hazard assessment. To simulate the ground motion caused by the 2009, Mw 4 earthquake, occurred south-east of the city, a hybrid technique is used. It combines two methods: the analytical modal summation and the numerical finite difference, taking advantage of the merits of both. The modal summation is applied to simulate wave propagation from the source to the sedimentary basin and finite differences to propagate the incoming wavefield in the laterally heterogeneous part of the structural model that contains the sedimentary basin. Time and frequency domain parameters are simulated along 2 (E-W and SE-NW) profiles for various stations.

For the protection of cultural heritage and the design of strategic buildings and critical infrastructures, when it is necessary to consider extremely long time intervals, the standard probabilistic estimates of seismic hazard (PSHA) are by far not applicable. The heuristic limitations are, indeed, a major limit of PSHA, whose results, extrapolating ground motion with an infinitely long return period from a few hundreds years of the available earthquake catalogues, may turn out to be a purely numerical artefact. A viable alternative, capable of minimizing the drawbacks of PSHA is represented by the use of a scenario-based methodology, named neo-deterministic approach (NDSHA), which relies on observable data and is based on the physical modelling of seismic waves generation and propagation processes. The NDSHA naturally supplies realistic time series of ground motion, which represent also reliable estimates of ground displacement readily applicable to seismic isolation techniques, useful to preserve historical monuments and relevant man made structures. In addition, an integrated NDSHA approach has been developed that allows for the operational definition of time-dependent scenarios of ground shaking, through the routine updating of formally defined earthquake predictions. The integrated NDSHA procedure, which is currently applied to the Italian territory, combines different pattern recognition techniques, designed for the space-time identification of strong earthquakes, with algorithms for the realistic modelling of ground motion. Accordingly, when an alarm is declared, a set of scenarios of expected ground shaking at bedrock, associated with the alarmed areas identified by means of the algorithms CN and M8S, can be readily computed by means of full waveform modelling, both at regional and local scale, considering all of the possible earthquake sources within the alerted areas. For the relevant sites, further investigations can be performed taking into account the local soil conditions, in order to compute the seismic input (realistic synthetic seismograms) for engineering analysis. The practical application of seismic input modelling for seismic isolation purposes, and particularly for the protection of historical buildings, has been already carried out for example for several sites, including the cities of Trieste (NE Italy) and Valparaiso (Chile) and the towns of Marigliano and Ercolano (Naples, Italy). A recent example of the practical advantages that can be provided by the time-dependent definition of ground-shaking scenarios is given by the Cathedral of Santa Maria di Collemaggio, which was severely damaged during the L’Aquila earthquake (6 April 2009). Based on the ongoing alert for the nearby CN region and the relevant ground shaking expected at the site, the restoration and isolation of the cathedral could have been timely completed, possibly limiting if not preventing the occurred damage. The relevance of the realistic modelling, which permits the generalization of empirical observations by means of physically sound theoretical considerations, is evident, as it allows for the optimisation of the structural design with respect to the site of interest. Moreover, the time information given by the intermediate-term middle-range earthquake prediction can enhance preparedness and planning of risk mitigation actions.

Ground motion has been computed for the 6 April 2009 earthquake (Mw=6.3) by using a hybrid method (modal summation and finite difference techniques) along a geological section crossing L'Aquilla. Sources have been simulated both as point and extended, with unilateral and bilateral ruptures. Spectral amplifications of about 10 have been found in correspondence of the cover of the Aterno river alluvial deposits and span a wide range of frequencies, that is various typologies of structures. In addition, the modelling has evidenced that whereas strong heterogeneitiies are present, for the same set of synthetic seismograms, the H/V spectral ratios are not able to evidence the spectral amplifications obtained with the 2D/1D response spectra ratios. Possible nonlinear soil effects have been evaluated for PGA values higher than 0.1-0.2 g, depending on the strain-dependent soil properties, with the linear equivalent approach, by using literature variations of shear moduli and damping with strain.

Una strategia efficace per la mitigazione del rischio sismico richiede la risposta ai seguenti quesiti: a) dove, quando e quanto forte un terremoto può colpire la regione in esame?, b) quali conseguenze ci si deve attendere qualora esso avvenga? La risposta alla prima domanda riguarda la previsione dei terremoti, mentre la seconda è oggetto degli studi di rischio sismico.

Scenari di pericolosità sismica per l' applicazione dell'isolamento sismico.

An integrated neo-deterministic approach to seismic hazard assessment has been developed that combines different pattern recognition techniques, designed for the space-time identification of strong earthquakes, with the procedure for the neo-deterministic assessment of seismic hazard. The integrated approach allows for a time dependent definition of the seismic input (realistic synthetic seismograms), through the routine updating of earthquake predictions. The time information given by the intermediate-term middle-range earthquake prediction can be used to enhance and optimize preparedness actions. Accordingly, when an alarm is declared, ground shaking scenarios at bedrock can be readily computed for the entire alerted area, as well as for the individual areas prone to strong earthquakes included in it, thus providing a reliable and reproducible picture of what should be expected when a strong earthquake occurs. For those sites where intensity values greater than VI (MCS) are estimated at bedrock, further investigations can be performed taking into account the local soil conditions, in order to compute the seismic input (realistic synthetic seismograms) for engineering analysis of relevant structures, such as historical and strategic buildings. A pilot application of the proposed approach, including a detailed evaluation of the expected ground mo-tion accounting for site effects, has been carried out, among others, for the city of Trieste. Attention has been focused on Palazzo Carciotti, a masonry neoclassical palace, which has a prominent artistic relevance within the city. The palace is located in the ancient part of Trieste, where soft superficial sediments of poor geotech-nical characteristics are present. Ground motion modeling shows that these site conditions may lead to a peak ground acceleration value of 0.2 g, greater than the value obtained at bedrock. The computed synthetic seis-mograms have been used as seismic input for the engineering seismic safety appraisal of the building. Three kind of dynamic analysis have been carried out: a) a modal analysis, using response spectrums calculated both from synthetic seismograms and according to Eurocode 8, b) a push-over analysis, c) a dynamic push-over analysis, which have evidenced that a strong earthquake (M=6.5) occurring in the proximity of Trieste (21 km far from the considered site) could seriously compromise the stability of the structure. The realistic computation of the seismic input, taking in account the local soil conditions, combined with the evaluation of the seismic response of buildings provides an effective approach to the assessment seismic risk.

Dalle previsioni a medio termine agli scenari di scuotimento: metodologie di avanguardia per difendersi dai terremoti

This paper deals with the neo-deterministic definition of the seismic input in the municipality of Nimis (Italy), aimed at the design of residential seismically isolated buildings. The seismic input is defined by the computation of realistic synthetic seismograms considering different levels of detail for the earthquake source, both for a bedrock model and taking into account the specific site conditions. The horizontal response spectrum, calculated in the centre of the municipality by modelling the most dangerous source, advises against the construction of a building with a fixed base, but it is compatible with the seismic isolation, and it has been, therefore, used for the design of a residential seismically isolated building. The maximum displacement for the isolation system has been estimated about 17 cm, a value much lower than that provided by the code design response spectrum (28 cm). The importance of the realistic modelling, which permits the generalization of empirical observations by means of, physically sound, theoretical considera- tions, is evident, as it allows for the optimisation of the structural design with respect to the site of interest

Nimis (Udine) has been included in seismic zone I by the new Italian seismic code, which specifies criteria for the design and construction of new buildings. The study presented in this paper deals with the deterministic definition of the seismic input in the municipality of Nimis, aimed at the design of residential seismic isolated buildings. The seismic input is defined by the computation of synthetic seismograms at different level of detail. In the first approximation a deterministic zoning at national scale has been defined to characterize the ground motion (in terms of displacement, velocity and DGA) at the bedrock. In this way a DGA value consistent with that one provided by the new Italian seismic code is obtained. In a second approximation the detailed modelling of seismic ground motion in Nimis has been performed considering selected scenario earthquakes and the specific local conditions at the site of Nimis. The most dangerous scenario considered, which corresponds to the source of the 1976 Friuli earthquake, leads to a peak ground acceleration al least twice than that obtained at national scale. This demonstrates the relevance of taking into account local geological conditions for a detailed modelling of ground motion. The corresponding horizontal response spectrum, calculated in the centre of the municipality using this source, has been used for the design of a residential seismic isolated building. This spectrum advises against the construction of a building with a fixed base, but it is compatible with the seismic isolation: the maximum displacement for the isolation system has been estimated about 15 cm, a value much lower than that provided by the code design response spectrum (28 cm). The importance of the realistic modelling is evident, as it allows for the optimisation of the structural design with respect to the site of interest.

È stato affrontato il problema della definizione della pericolosità sismica (input sismico) tramite la modellazione dei possibili scenari compatibili con la storia sismica e la sismotettonica della zona di Nimis. I sismogrammi sintetici, che tengono conto dei principi fondamentali della fisica relativi alla generazione e propagazione delle onde sismiche, consentono di colmare le lacune nei dati, inevitabilmente incompleti a causa della limitata finestra temporale coperta dalle osservazioni, rispetto ai tempi dei processi geologici causa dei terremoti. L’elevata sismicità della zona rende complessa la realizzazione di strutture resi- denziali utilizzando tecniche antisismiche tradizionali, mentre risulta particolarmente vantaggioso l’impiego di tecniche avanzate, quali l’isolamento sismico, che consente, nell’ambito della normativa vigente, la realizzazione di costruzioni con interessanti soluzioni architettoniche.

A detailed modelling of the ground motion in Trieste has been done for some scenario earthquakes, compatible with the seismotectonic regime of the region. Three-component synthetic seismograms (displacements, velocities and accelerations) have been analyzed to obtain significant parameters of engineering interest. The definition of the seismic input, derived from a comprehensive set of seismograms analyzed in the time and frequency domains, represents a powerful and convenient tool for seismic microzoning. Both modelling and observations show that site conditions in the centre of Trieste can amplify the ground motion at the bedrock by a factor of five, in the frequency range of engineering interest.

The seismic hazard map in North China i assessed using a deterministic approach. The seismic sources are represented at a set of grid points located at distances of 0.2° from each other. The main inputs for this computation are earthquake catalogue, source mechanisms, the level of seismic activity and the structural models. Synthetic seismograms are generated by different sources, and are used to obtain the distribution map of the maximum ground motion and Design Ground Acceleration (DGA). In the research area, the highest of DGA is at east of Beijing, with the value as high as 0.75 g.

Il progetto è orientato al problema della prevenzione dei disastri: valutazione, prevenzione e ubicazione del rischio, in connessione con l’attività sismica e le vibrazioni artificiali. La definizione realistica della sollecitazione sismica è stata ottenuta col calcolo di un ampio insieme di serie temporali (sismogrammi sintetici) e relative informazioni spettrali, corrispondenti ai possibili scenari sismotettonici. La tecnica innovativa di modellazione, che costituisce il filo conduttore dell’intero progetto, prende in considerazione l’origine delle onde sismiche, la loro propagazione e gli effetti locali nel luogo di interesse. Ciò è stato realizzato utilizzando i principi fisici della generazione e propagazione delle onde nei mezzi anelastici, evitando di rifarsi ad un approccio convolutivo che si è dimostrato del tutto irrealistico, soprattutto in caso di strutture geologiche complesse, che sono poi le più interessanti dal punto di vista pratico. Molte tecniche, che sono state proposte per stimare empiricamente gli effetti locali tramite la convoluzione di osservazioni con segnali, calcolati in corrispodenza di modelli semplificati, forniscono informazioni attendibili sulla risposta sismica del sito a fasi sismiche non interferenti. Essi sono inadeguati nella maggior parte dei casi reali, dove la sequenza sismica è formata invece da diverse onde interferenti. La disponibilità di simulazioni numeriche realistiche ha reso possibile una stima attendibile dell’effetto di amplificazione locale, persino nel caso di strutture geologiche complesse, quando sono disponibili i parametri geotecnici, litologici e geofisici, i dati topografici, tettonici, storici e paleosismologici, nonche’ i modelli sismotettonici. La modellazione realistica dei movimenti tellurici è un punto fondamentale nella preparazione di scenari di scuotimento del suolo (groundshaking) che rappresentano un valido ed economico strumento per la microzonazione sismica. Tale conoscenza è facilmente utilizzabile negli ambiti dell’ingegneria civile per i progetti di nuove costruzioni antisismiche e per migliorare le strutture già esistenti, ed inoltre rappresenta un ottimo strumento nell’ambito dei servizi di prevenzione della protezione civile. Vene Qui presentata una selezione dei principali risultati ottenuti nelle città di: Algeri, Pechino, Bucarest, Cairo, Debrecen, Delhi, Napoli, Roma, Russe, Santiago de Cuba, Sofia, Salonicco e Zagabria.

Synthetic seismograms (P-SV and SH waves) have been calculated along six profiles in SantiagodeCuba basin, with a cutoff frequency of 5 Hz, by using a hybrid approach (modal summation for a regional 1D structure plus finite differences for a local 2D structure embedded in the first). They correspond to a scenario earthquake of MS=7 that may occur in Oriente fault zone, directly south of the city. As initial data for a seismicmicrozoning, the characterisation of earthquake effects has been made considering several relative (2D/1D) quantities (PGDR, PGVR, PGAR, DGAR, IAR—ratios of peak ground values of displacement, velocity and acceleration, and of design ground acceleration and Arias intensity-, etc.) and functions representative of the groundmotion characteristics in soil (2D) with respect to bedrock (1D). The functions are the response spectra ratio RSR(f), already routinely used in this kind of work, and the elastic energy input ratio EIR(f), defined, for the first time, in this paper. These data, sampled at 115 sites within all the profiles have been classified in two steps, using logical combinatory algorithms: connected components and compact sets. In the first step, from the original groundmotion parameters or functions extracted from the synthetic seismograms, nine sets have been classified and the partial results show the spatial distribution of the soil behaviour as a function of the component of motion. In the second step, the results of the classification of the nine sets have been used as input for a further classification that shows a spatial distribution of sites with a quasi-homogeneous integral groundmotion behaviour. By adding the available geological surface data, a microzoning scheme of SantiagodeCuba basin has been obtained.

A new hybrid MS-BIE method based on the modal summation (MS) and the boundary integral equation (BIE) methods is developed. The proposed hybrid technique allows the theoretical seismogram synthesis taking into consideration seismic source properties, non-homogeneous wave path and local site effects as layering with non-parallel interfaces and free-surface topography. Each of the two techniques is applied in the part of the structural model where it works more efficiently. The MSM is applied for numerical simulation of wave propagation from the source position to the local region of interest, while the BIEM is used inside the local multi-layered geological region. The accuracy and validation study of the proposed method is presented by solution of numerical examples simulation different seismic scenarios. The comparison between the MS-BIEM synthetic seismograms and ones obtained by pure analytical and/or other hybrid methods has been evaluated and discussed.

A seismic hazard map of the territory of India and adjacent areas has been prepared using a deterministic approach based on the computation of synthetic seismograms complete with all main phases. The input data set consists of structural models, seismogenic zones, focal mechanisms and earthquake catalogues. There are few probabilistic hazard maps available for the Indian subcontinent, however, this is the first study aimed at producing a deterministic seismic hazard map for the Indian region using realistic strong ground motion modelling with the knowledge of the physical process of earthquake generation, the level of seismicity and wave propagation in anelastic media. Synthetic seismograms at a frequency of 1 Hz have been generated at a regular grid of 0.2◦ × 0.2◦ by the modal summation technique. The seismic hazard, expressed in terms of maximum displacement (Dmax), maximum velocity (V max), and design ground acceleration (DGA), has been extracted from the synthetic signals and mapped on a regular grid over the studied territory. The estimated values of the peak ground acceleration are compared with the observed data available for the Himalayan region and are found to be in agreement. Many parts of the Himalayan region have DGA values exceeding 0.6 g. The epicentral areas of the great Assam earthquakes of 1897 and 1950 in northeast India represent the maximum hazard with DGA values reaching 1.2–1.3 g. The peak velocity and displacement in the same region is estimated as 120–177 cm s−1 and 60–90 cm, respectively.

Several algorithms, structured according to a general pattern-recognition scheme, are currently applied for the space-time identification of strong earthquakes in the Italian territory. Two, namely CN and M8 algorithms, for intermediate-term medium-range earthquake prediction purposes and one for the recognition of earthquake-prone areas. These algorithms can be viewed as independent experts, hence they can be combined to better constrain the alerted seismogenic area. We examine here the possibility to integrate the intermediate-term medium-range earthquake predictions with the procedures developed for the recognition of strong earthquake prone areas and for the deterministic assessment of seismic hazard. This permits to associate the alarms declared by the prediction algorithms to a set of possible seismic ground motion scenarios. We analyse in detail the case of CN predictions and we supply examples of scenarios corresponding to possible events with M6.5, that turn out to be the closest to several cities in Italy. A practical advantage of the described procedure is the time information given by the intermediate-term earthquake prediction that is very useful to plan preparedness and rescue actions and to define priority criteria for the more detailed studies required by seismic microzonation.

A hybrid technique consisting of modal summation and subsequent ®nite differences modelling is applied for the computation of synthetic accelerograms along a pro®le crossing the city of Zagreb, the capital of Croatia. Assuming the source geometry is known, the ampli®cation properties of the underlying soil may be determined by comparison of synthetics and their response spectra computed for a bedrock model with the ones obtained under the assumption of a realistic laterally varying local model. The peak ground acceleration is larger by a factor of up to 3.5 than the value obtained for the bedrock model. The ampli®cation of the response spectra is most prominent for frequencies below 2 Hz, and increases sharply to the SW from the mapped fault running through the centre of the city. q 2002 Published by Elsevier Science Ltd.

The modal summation method to compute synthetic seismograms is applied to carry out a study of seismic zonation in Albania. From a seismotectonic synthesis and the available earthquake data, eight seismogenic zones are defined and for each of them, a characteristic focal mechanism is selected. A new seismic velocity model is used in the computations and is constructed on the basis of previous studies. Correlation relations between the maximum intensity values observed and the ground motion parameters obtained from this procedure are derived. The distribution of the calculated values of displacement, velocity and acceleration, will contribute to the quality of anti-seismic design practice in Albania and to the mitigation of earthquake consequences.

We illustrate the work done in the framework of a large international cooperation, showing the very recent numerical experiments carried out within the framework of the EC project 'Advanced methods for assessing the seismic vulnerability of existing motorway bridges' (VAB) to assess the importance of non-synchronous seismic excitation of long structures. The definition of the seismic input at the Warth bridge site, i.e. the determination of the seismic ground motion due to an earthquake with a given magnitude and epicentral distance from the site, has been done following a theoretical approach. In order to perform an accurate and realistic estimate of site effects and of differential motion it is necessary to make a parametric study that takes into account the complex combination of the source and propagation parameters, in realistic geological structures. The computation of a wide set of time histories and spectral information, corresponding to possible seismotectonic scenarios for different sources and structural models, allows us the construction of damage scenarios that are out of the reach of stochastic models, at a very low cost/benefit ratio.