Search

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 procedure we developed and applied to several relevant buildings of the Trieste Province (Provincia di Trieste, 2015) shown in Figure 1, leads to the seismic veri cation of a building by: a) use of a scenario based neo- deterministic 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 of the seismologist and the civil engineer, from the seismic input de nition to the monitoring of the response of the building in the calculation phase. The vibrometry study allows the engineer to adjust the computational model in the direction suggested by the experimental re- sult of a physical measurement.

A first-order deterministic seismic zoning of Italy, based on the compution of synthetic seismograms [10,27,28] lead to theoretical peak values estimates for the Umbria-Marche region that are well in agreement with the peak values observed during the sequence started on september 26,1997.

Modellazione del moto del suolo atteso per vari scenari sismici

The earthquake record and the Code for design and construction in seismic regions in Bulgaria have shown that the territory of the Republic of Bulgaria is exposed to a high seismic risk due to local shallow and regional strong intermediate‐depth seismic sources. The available strong motion database is quite limited, and therefore not representative at all of the real hazard. The application of the neo‐deterministic seismic hazard assessment procedure for two main Bulgarian cities has been capable to supply a significant database of synthetic strong motions for the target sites, applicable for earthquake engineering purposes. The main advantage of the applied deterministic procedure is the possibility to take simultaneously and correctly into consideration the contribution to the earthquake ground motion at the target sites of the seismic source and of the seismic wave propagation in the crossed media. We discuss in this study the result of some recent applications of the neo‐deterministic seismic microzonation procedure to the cities of Sofia and Russe. The validation of the theoretically modeled seismic input against Eurocode 8 and the few available records at these sites is discussed.

In recent years, probabilistic seismic hazard assessment (PSHA) has been the most common procedure to evaluate the potential effects of future earthquakes. It assesses the probability that some measure of ground motion intensity (e.g., the peak ground acceleration) exceeds some threshold during a given period of time (most commonly 10% in 50 years’time). In Europe and the Mediterranean region, different efforts starting in the 1990s have provided several regional hazard models at the continental scale (e.g., Jiménez et al., 1999, 2001; Giardini et al., 2003) with the latest model in Woessner et al. (2015) deriving a complete set of harmonized seismic hazard results and associated uncertainties for Europe. Site studies for nuclear power plants were the onset for the development of seismic hazard in Spain at the beginning of the 1970s. At that time, the existing regulations demanded classical deterministic analysis. Therefore, only a few works included either statistical or probabilistic approaches, which later on were widely applied in most of the regional hazard studies carried out in Spain in the 1980s and 1990s (see, e.g., Martín, 1984; Muñoz et al., 1984; Litehiser and Marrone, 1991, among others). It was for the first time in 1994 when the update of the Spanish Building Code incorporated a probabilistic seismic hazard map to define the basic seismic action (Martín, 1995). Studies incorporating alternative statistical analysis, including Bayesian techniques, of hazard parameters were also applied in the last 1980s and early 1990s (see, e.g., García-Fernández et al., 1989; Egozcue et al., 1991)

The preliminary regional seismic hazard map for Pakistan and adjoining regions published by Sarwar et al. (2018) is here updated. The earthquake catalog by Khan et al. (2018) is adopted, and the latest computer codes for the neo-deterministic seismic hazard assessment (NDSHA) are used. At the regional scale, NDSHA is based on the generation of synthetic seismograms at a regular grid of 0.2 degrees × 0.2 degrees. The main input is a set of earthquake sources and layered anelastic structural models. As a result, seismic hazard maps are produced in terms of maximum displacement (Dmax), maximum velocity (Vmax), and design ground acceleration. The comparison between probabilistic (PSHA) and NDSHA maps for Pakistan shows that the currently adopted PSHA maps generally underestimate the level of ground shaking that might be expected for future events.

The Suez Canal Economic Zone (SCZone) is a mega project in Egypt that was launched to increase the role of the Suez Canal region in international trading and to develop the urbanization of the region. The reliable assessment of seismic hazard is a crucial input information for the designer and planner of all projects in this area. In this study, an updated seismic hazard map for Suez Canal region that incorporates revised historical earthquake catalogs, morphostructural zonation data (MZ), revised focal mechanism solutions and mechanical models of the lithospheric structure is provided. This is done within the framework of the Neo-Deterministic Seismic Hazard Assessment (NDSHA) procedure that may efficiently incorporate earthquake source rupture data, geological information and any reliable new information to adequately compute the earthquake ground motion maps, like PGA, PGV and PGD. This methodology provides a comprehensive source of ground motion records (acceleration, velocity, displacement) for Egypt where a substantial challenge is posed by the lack of recorded data. To consistently assess the uncertainty of our understanding of the seismic hazard and its effect on critical structures a sensitivity analysis is performed varying, for example, (a) source focal mechanism, (b) directivity (c) rupture process and (d) seismotectonic model. Starting from the initial definition of the source, bedrock and site properties based on the available knowledge of the characteristics of the different earthquake scenarios and of the soil structural properties of the area deduced from the ambient noise array measurements, a set of ground shaking scenarios have been computed at the selected profile crossing the Suez Canal. Variations of the ground shaking scenarios are evaluated looking basically at: (a) the amplitudes measured on the waveforms and the response spectra, (b) the changes in the shaking duration and (c) the modifications in the amplification patterns. Finally, the seismic input (e.g. response spectra, time histories) at the tunnel site that undergoes the Suez Canal to connect Sinai peninsula with the western side of the country is provided.

The neo-deterministic seismic hazard assessment (NDSHA), developed at the University of Trieste (UT), has emerged as an attractive tool for predicting the ground motion for given seismic sources and known earth structure. This method, a computationally intensive procedure, is based on physical modeling of wave propagation and seismic source process. Under ongoing research and academic collaboration program between UT and BUET, NDSHA studies have been performed for Bangladesh. This chapter briefly presents significant results obtained under this initiative. Results obtained are compared with the seismic zoning map in the updated Bangladesh National Building Code (BNBC-2020). The seismicity and seismo-tectonics of Bangladesh and the adjoining region are also briefly discussed.

Many devastating earthquakes inflicted heavy casualties and property losses in the seismically active China Seismic Experimental Site area (CSES: 97.5° ~ 105.5°E, 21° ~ 32°N). We performed a first-order seismic zoning based on Neo-deterministic Seismic Hazard Assessment (NDSHA) in the study area delimited by 94° ~ 108°E and 19° ~ 35°N, containing the South-East margin of the Tibetan Plateau and the Sichuan-Yunnan region. The seismic hazard is expressed by maps of peak ground displacement (PGD), peak ground velocity (PGV) and design ground acceleration (DGA) values, extracted from synthetic seismograms computed at a regional scale and mapped on a regular grid of 0.2° × 0.2° over the study area. For the computation of synthetic seismograms, we considered and updated all the available geophysical-geological-tectonic information, including historical and instrumental earthquake catalogues, seismogenic zones, seismogenic nodes, focal mechanisms, and geophysical structural models. We tested the performance of our assessments with available data (i.e., after the Great Wenchuan (2008, May 12th, Ms = 8.0) and Lushan (2013, April 20th, Ms = 7.0) earthquakes) and verified the negligible influence of large events located “far” from the study area. The results indicate the high seismic hazard of the region, with a particular attention (i.e., where DGA > 0.6 g) to the areas located around the main fault zones, e.g., the Longmenshan, Anninghe and Zemuhe Fault Zones. These first-order NDSHA zoning findings may serve as a knowledge basis to support both large- to mid-range preparedness actions and (multi-scenario) site-specific studies.

Current computational resources and physical knowledge of the seismic wave generation and propagation processes allow for reliable numerical and analytical models of waveform generation and propagation. From the simulation of ground motion, it is easy to extract the desired earthquake hazard parameters. Accordingly, a scenario-based approach to seismic hazard assessment has been developed, namely the neo-deterministic seismic hazard assessment (NDSHA), which allows for a wide range of possible seismic sources to be used in the definition of reliable scenarios by means of realistic waveforms modelling. Such reli- able and comprehensive characterization of expected earthquake ground motion is essential to improve building codes, particularly for the protection of critical infrastructures and for land use planning. Parvez et al. (Geophys J Int 155:489–508, 2003) published the first ever neo-deterministic seismic hazard map of India by computing synthetic seismograms with input data set consisting of structural models, seismogenic zones, focal mechanisms and earthquake catalogues. As described in Panza et al. (Adv Geophys 53:93–165, 2012), the NDSHA methodology evolved with respect to the original formulation used by Parvez et al. (Geophys J Int 155:489–508, 2003): the computer codes were improved to better fit the need of producing real- istic ground shaking maps and ground shaking scenar- ios, at different scale levels, exploiting the most significant pertinent progresses in data acquisition and modelling. Accordingly, the present study supplies a revised NDSHA map for India. The seismic hazard, expressed in terms of maximum displacement (Dmax), maximum velocity (Vmax) and design ground acceleration (DGA), has been extracted from the synthetic signals and mapped on a regular grid over the studied territory.

Ischia island, in the province of Naples, is a densely populated volcanic island, in which small to moderate magnitude earthquakes occur. Due to the very shallowdepth of such events (< 2 km), they can generate serious damage and casualties, up to the complete destruction of urban centers located within short epicentraldistance. Almost all of the earthquakes at Ischia island occur at shallow depth, beneath the Northern slopes of the Mt. Epomeo horst, which is located very close to thetown of Casamicciola. In fact, Casamicciola was completely destroyed by the 1883 earthquake (2313 victims) and experienced intensities up to XI degree on theMercalli scale. Historical records show that the background seismicity here is almost absent, but larger earthquakes tend to occur in clusters, lasting some decadesand with intervals between consecutive events on the order of years to decades. The clustering in time and the very shallow hypocentres, which cause, with respect totectonic earthquakes of similar magnitude, larger effects though limited to a relatively small area, make the seismicity in this island very peculiar. Despite suchdestructive record, till now official hazard maps strongly underestimated the seismic hazard in this area. On August 21st 2017, a very shallow earthquake with rathersmall magnitude struck the area of Casamicciola, killing two people, injuring many more and causing huge damage and partial to total collapse of edifices located justabove the earthquake fault.The maximum acceleration recorded for this earthquake exceeded by more than a factor of two the reference acceleration that should be sustained by edifices,according to official hazard maps. We propose here a complete procedure to assess and mitigate the risk, which can be rapid and economically affordable and, at thesame time, can avoid further grief due to possible occurrence of other destructive earthquakes within a short time interval. We describe the most likely buildingcollapse and casualty scenarios, in case that low-to-moderate magnitude earthquakes would occur before the edifices would be appropriately reinforced and secured.Our scenarios demonstrate the urgent need for securing operations. The proposed procedures for assessing seismic hazard and for securing urban areas provide anexample that is potentially applicable to the whole Italian peninsula. They may allow in fact the mitigation of the destructive impact of a large number of earth-quakes, which in Italy are often characterized by low or moderate magnitudes.

The Neo-Deterministic Seismic Hazard Assessment (NDSHA) procedure for the development of seismic hazard maps at the regional scale has been validated by all the events occurred in regions where NDSHA maps were available at the time of the quake. NDSHA method reliably and realistically simulates the wide suite of earthquake ground motions that may impact civil populations as well as their heritage buildings. The scenario based NDSHA’s modeling technique is developed from comprehensive physical knowledge of: (i) the seismic source process; (ii) the propagation of earthquake waves; and (iii) their combined interactions with site effects. A useful safety factor conceptually similar to the ones used in structural engineering can be used to set the estimated magnitude of the scenario events. Using the signals generated by NDSHA, well rooted on the fundamental laws of physics and on the experimental evidence, a number of possible structural engineering approaches become available.

Throughout time, the area of historical Cairo has been affected by several earthquakes from near and distant seismogenic zones. The maximum earthquake intensity reported in Cairo is VII, on the Modified Mercalli Intensity scale, due to the 1992 Cairo earthquake (Mw=5.9). About 212 Coptic and Islamic monuments were damaged. The spatial distribution of damage, suggests the occurrence of strong local site effects in combination with high vulnerability of the cultural heritage buildings. This study presents the application of a novel seismic hazard analysis approach at a local scale based on physics-based ground motion simulations. A site-specific multi-scenario seismic input (ground motion time histories and response spectra) is computed at a heritage building in Cairo, considering the local site effect. The seismic input is calculated in three steps: a regional scale analysis followed by a site-specific analysis and the combinations of the computed scenarios ground motion. In the regional scale analysis synthetic accelerograms are computed at the site bedrock. Then, the site-specific analysis is performed to calculate the site surface ground motions or response spectra considering the local site effect. Three earthquake scenarios have been considered, characterized by different locations, magnitudes, and fault configurations. The last step consists in the combination of the computed scenario ground motion into one single multi-scenario seismic input specific for the site of interest. This input is represented by spectral ordinates and their variability. For the engineering purpose of time history analysis, the method allows also to extract the computed site specific physics-based accelerograms, requiring no amplitude scaling nor filtering by magnitudes, distances, or site classifications, as usually done with real ground motion records.

Seismic hazard maps for Alborz region (north of Iran) and adjacent areas are prepared using the neo-deterministic seismic hazard assessment (NDSHA) based on the computation of synthetic seismograms at the regional scale. The study area is zoned according to different geophysical structural models delimited at the surface by polygons, used to define the mechanical properties of the source-site paths. We have refined the velocity structures of Iran, as obtained from surface waves tomography, to obtain the velocity structure of Alborz region by applying the joint inversion of the P-wave receiver functions (PRF) and surface wave's dispersion. The input data set consists of attenuation-velocity structural models (representing bedrock conditions), seismogenic zones, focal mechanisms and the catalog of past seismicity. The seismic hazard, expressed in terms of maximum displacement (PGD), maximum velocity (PGV) and design ground acceleration (DGA), is extracted from the synthetic seismograms and mapped on a regular grid of 0.2° × 0.2° over the entire region. The results of this first order NDSHA zoning indicate a high seismic hazard in the Alborz region and may represent an important knowledge basis towards detailed and comprehensive seismic microzonation studies.

The aim of this work is two-fold: 1) to compare the results of national scale NDSHA modelling for the Italian region at 10 Hz cut-off, based on the relevant available knowledge, with observations (e.g., peak ground motion values) and existing empirical attenuation relations; 2) to update the scaling law for source spectra (SLSS) to be used for the selected area. The new set of source spectra, defined along the lines suggested by the comparison with empirical attenuation relations, produces acceptable results in terms of PGV and spectral acceleration at long periods. Synthetic PGA and SA at short periods show a faster attenuation with respect to the observed ones and, therefore, the effect of complex attenuation factors should be explored in future ad hoc studies.

A web application prototype is described, aimed at the generation of synthetic seismograms for user-defined earthquake models. The web application graphical user interface hides the complexity of the underlying computational engine, which is the outcome of the continuous evolution of sophisticated computer codes, some of which saw the light back in the middle 1980s. With the web application, even the non-experts can produce ground shaking scenarios at the local or regional scale in very short times, depending on the complexity of the adopted source and medium models, without the need of a deep knowledge of the physics of the earthquake phenomenon. Actually, it may even allow neophytes to get some basic education in the field of seismology and seismic engineering, due to the simplified intuitive experimental approach to the matter. One of the most powerful features made available to the users is indeed the capability of executing quick parametric tests in near real-time, to explore the relations between each model’s parameter and the resulting ground motion scenario. The synthetic seismograms generated through the web application can be used by civil engineers for the design of new seismo-resistant structures, or to analyse the performance of the existing ones under seismic load.

This paper describes the outcome of the advanced seismic hazard and seismic risk estimates recently performed for the city of Sofia, based on the state-of-the-art of knowledge for this site. Some major results of the neo-deterministic, scenario-based, seismic hazard assessment approach (NDSHA) to the earthquake hazard assessment for the city of Sofia are considered. Further validations of the recently constructed synthetic strong motion database, containing site and seismic source-specific ground motion time histories are performed and discussed. Displacement and acceleration response spectra are considered. The elastic displacement response spectra and displacement demand are discussed with regard to earthquake magnitude, seismic source-to-site distance, seismic source mechanism, and local geological site conditions. The elastic response design spectrum from the standard pseudo-acceleration, versus natural period, T n, format, converted to a capacity diagram in S a − S d format is discussed in the perspective of the Eurocode 8 provisions. A brief overview of the engineering applications of the seismic demand obtained making use of the NDSHA is supplied. Some applications of the outcome of NDSHA procedure for engineering purposes are shown. The obtained database of ground shaking waveforms and time-histories, computed for city of Sofia is used to: (1) extract maximum particle velocities; (2) calculate the space distribution of the horizontal strain factor Log10 e; (3) estimate liquefaction susceptibility in terms of standard penetration test, N values, and initial over burden stress; (4) estimate damage index distribution; and (5) map the distribution of the expected pipe breaks and red-tagged buildings for given scenario earthquakes, etc. The theoretically obtained database, based on the simultaneous treatment of the data from many disciplines, contains data fully suitable for practical use. The proper use of this database can lead to a significant seismic vulnerability reduction and thus contributes to earthquake preparedness.

The P-SV- and SH-wave field in the Talchir Basin is simulated along eight profiles: four profiles strike across the basin and the other four along the basin. The hybrid method, which combines two computational techniques, modal summation and finite differences, is used to produce multiphase synthetic seismograms. An M = 6 earthquake is considered, with hypocenter along the North Orissa Boundary Fault (NOBF) at a depth of 5 km and with the focal mechanism parameters: dip = 90°, strike = 160° and rake = 180°. The peak acceleration (A MAX ) along each profile is determined considering the maximum acceleration obtained at the horizontal components. The response spectra ratio (RSR) as a function of frequency is computed for the eight profiles and the higher amplification is seen to increase in correspondence with the thicker sedimentary cover, especially for the radial component. Higher site amplification for all the profiles is observed in the frequency range from 0.5 to 1.4 Hz. To validate the obtained site-effects, the sources, for the profiles across the basin, are placed near to the southern end of the profile and the site amplifications are recomputed. Even if the spatial distribution of A MAX is mainly controlled by the epicentral distance, i.e. the geometrical spreading prevails on local soil effects, the RSR shows a pattern that can be easily correlated with the local site conditions. The RSR at the intersection of the profiles is dependent not only upon the local lithology and sediment thickness but also upon the epicentral distance. The Talchir Basin is classified into three zones based on the RSR values: low RSR zone (1.6–1.9), intermediate RSR zone (2.0–2.8) and high RSR zone (2.9–5.2). The PGA estimated for the bedrock model by Bhatia et al. (1999) for the study region is around 0.05 to 0.10 g while the Indian seismic zonation map estimated it to be in the range from 0.1 to 0.2 g. In the present study, that considers the effects of lateral variations in the structure, the PGA is estimated to be as high as 0.55 g along the BA profile.

A hybrid method for the calculation of realistic synthetic seismograms in laterally heterogeneous, anelastic media has been used to model the ground motion in Tehran city. The synthetic records compare reasonably well with the observed ground motion due to the 2004 Firozabad Kojor earthquake located 60 km north of Tehran. The ratio between the response spectrum for the signals calculated along a laterally varying structure, Sa(2D), and that for the signals at the bedrock regional reference structure, Sa(1D), shows a high amplification of seismic waves in Tehran. The procedure can be readily implemented for the entire Tehran city, which experienced large historical earthquakes in the past, simply by extending the analysis, made so far, in space and to different scenario earthquakes, consistent with the local and regional tectonics.

A reliable and comprehensive characterization of expected seismic ground shaking is essential to improve building codes, particularly for the protection of critical infrastructures and for land use planning. So far, one of the major problems in classical methods for seismic hazard assessment consisted in the adequate characterization of the attenuation models, which may be unable to account for the complexity of the medium and of the seismic sources and are often weakly constrained by the available observations. Current computational resources and physical knowledge of the seismic waves generation and propagation processes allow nowadays for viable numerical and analytical alternatives to the use of attenuation relations. Accordingly, a scenario-based approach to seismic hazard assessment has been developed, namely the neo-deterministic approach (NDSHA), which allows considering a wide range of possible seismic sources as the starting point for deriving scenarios by means of full waveforms modelling. The method does not make use of attenuation relations and, thanks to advanced computational infrastructures, permits to carry on parametric analysis and stability tests that contribute characterizing the related uncertainties, as well as to fill in the unavoidable gaps in available observations. Results from preliminary application of NDSHA method to regional scale seismic hazard assessment (ground motion at bedrock) and tsunami scenarios modelling for the Gujarat territory are illustrated. The resulting estimates are compared with available information about intensities from past earthquakes, as well as with recently developed probabilistic seismic hazard map of Gujarat.

The aim of our study is to determine the design ground acceleration values at different parts of Debrecen along two profiles crossing the city. Synthetic seismograms are computed by the so called “hybrid technique”. This technique consists of the modal summation method, followed by finite difference modelling. Two independent computations have been performed using two different seismic sources and profiles. In both computations the seismic sources have been located in the so called “Mobile Zone”. The Mobile Zone is a seismically active fault system between the villages of Hosszupalyi and Galospetri. The focal mechanism and the homogeneous and heterogeneous parts of the profile are known from geophysical and geological data of the investigated area. The maximum response spectra ratio values of the horizontal component are found below 1 Hz all along the profile and the frequencies below 1 Hz are in good agreement with the natural frequencies of the multi-storeyed buildings. Computed effective peak acceleration (EPA) values are found to be in good agreement also with the higher than 6° MSK macroseismic intensity values estimated from the assessment records of damages wrought by the 1834 Ermellek earthquake.

We conducted a tomographic inversion of Rayleigh-wave dispersion to obtain 2D phase and group velocity tomographic images in the 10-100 s period range and shear-wave velocity structures for the Iranian plateau. For this purpose, the fun- damental mode of Rayleigh waves, recorded along 1586 paths by 29 broadband sta- tions, was identified by applying the frequency time analysis (FTAN) to each epicenter-station path which simultaneously satisfies the two-station method condi- tions. The fundamental modes identified by FTAN have been used to determine the path-average interstation phase and group velocities at selected periods. With this pro- cedure, 243 group and phase velocity dispersion curves were processed to obtain to- mographic maps by applying the Yanovskaya-Ditmar formulation for periods in the 10-100 s range. Averaged dispersion curves of phase and group velocities, which represent six rather homogeneous regions, are computed. Finally, we used a fully non- linear inversion procedure to derive tomographic images of the elastic structure of the lithosphere and asthenosphere of the six main structural and seismotectonic features of the Iranian plateau. The dense path coverage in the Iranian plateau permits us to pro- duce images that have substantially higher lateral resolution compared to images cur- rently available from global and regional group velocity studies. Tomographic maps at high frequencies are well correlated with the upper crust structure, especially with sediment layers thickness. Estimated shear-wave velocity structures are well corre- lated with the shield-like lithosphere structure in Zagros. A low-velocity zone (LVZ) is not detected in Alborz or the south Caspian basin, which can imply thrusting of the oceanic crust of the southern Caspian Sea under the Alborz to the south. LVZs are derived for the region east of Iran, central Iran, and Kopeh Dagh.

Seismic hazard assessment can be performed following a neo-deterministic approach (NDSHA), which allows to give a realistic description of the seismic ground motion due to an earthquake of given distance and magnitude. The approach is based on modelling techniques that have been developed from a detailed knowledge of both the seismic source process and the propagation of seismic waves. This permits us to define a set of earthquake scenarios and to simulate the associated synthetic signals without having to wait for a strong event to occur. NDSHA can be applied at the regional scale, computing seismograms at the nodes of a grid with the desired spacing, or at the local scale, taking into account the source characteristics, the path and local geological and geotechnical conditions. Synthetic signals can be produced in a short time and at a very low cost/benefit ratio. They can be used as seismic input in subsequent engineering analyses aimed at the computation of the full non-linear seismic response of the structure or simply the earthquake damaging potential. Massive parametric tests, to explore the influence not only of deterministic source parameters and structural models but also of random properties of the same source model, enable realistic estimate of seismic hazard and their uncertainty. This is particular true in those areas for which scarce (or no) historical or instrumental information is available. Here we describe the implementation of the seismological codes and the results of some parametric tests performed using the EU-India Grid infrastructure.

SUMMARY The regional seismic hazard in Egypt is assessed using a deterministic approach based on the computation of synthetic seismograms at a set of gridpoints located at distances of 0.2u from each other. The main input for this computation are earthquake sources and structural models. The earthquake sources are parametrized using focal mechanisms, seismogenic areas and regional seismicity. A number of deep seismic profiles have been used to define the crustal structures. Similar sets of gravity profiles have been used to define the density of the layers. The peak displacement (DMAX), peak velocity (VMAX) and design ground acceleration (DGA) are chosen and plotted to construct the seismic hazard maps. There are similarities between computed and observed amplitudes of ground motion in terms of their values and spatial distributions. The results obtained from the deterministic and probabilistic approaches are comparable. The areas of high seismic hazard level are of great socio-economic importance.

Some of the elements of regional seismic hazard in Croatia are assessed by computing synthetic accelerograms at a predetermined set of sites. The input dataset consists of structural models, parameters of seismic sources, and an updated earthquake catalog. Synthetic strong-motion time series for frequencies below 1 Hz are computed on a grid of sites using the modal summation technique. The long-period hazard is described by the distribution of estimated peak values of ground displacement, velocity and acceleration, while the short-period hazard is represented by the map of design ground acceleration values (DGA). The highest values of DGA exceeding 0.35 g on the base-rock level are found in the southeastern coastal part of the country, in the greater Dubrovnik area.

—A deterministic seismic zoning of Cuba is performed by modelling, with modal summation, the complete P-SV and SH waves fields generated by point-source earthquakes buried in flat-layered anelastic media. The results of the computation, performed for periods greater than 1 second, are presented in two sets of maps of maximum displacement (d max), maximum velocity (v max) and design ground acceleration (DGA), obtained by using two different criteria in the definition of the input magnitude: (1) values reported in the earthquake catalogue (M obs) and (2) values determined from seismotectonic considerations (M max). A comparison with the results of a previous probabilistic seismic zoning is made to test the possibility of making intensity — ground motion conversion with the aid of log-linear regressions.

North Africa is one of the most earthquake-prone areas of the Mediterranean. Many devastating earthquakes, some of them tsunami-triggering, inflicted heavy loss of life and considerable economic damage to the region. In order to mitigate the destructive impact of the earthquakes, the regional seismic hazard in North Africa is assessed using the neo-deterministic, multi-scenario methodology (NDSHA) based on the computation of synthetic seismograms, using the modal summation technique, at a regular grid of 0.2 × 0.2°. This is the first study aimed at producing NDSHA maps of North Africa including five countries: Morocco, Algeria, Tunisia, Libya, and Egypt. The key input data for the NDSHA algorithm are earthquake sources, seismotectonic zonation, and structural models. In the preparation of the input data, it has been really important to go beyond the national borders and to adopt a coherent strategy all over the area. Thanks to the collaborative efforts of the teams involved, it has been possible to properly merge the earthquake catalogues available for each country to define with homogeneous criteria the seismogenic zones, the characteristic focal mechanism associated with each of them, and the structural models used to model wave propagation from the sources to the sites. As a result, reliable seismic hazard maps are produced in terms of maximum displacement (D max), maximum velocity (V max), and design ground acceleration.

The strong influence of lateral heterogeneities and of source properties on the spatial distribution of ground motion indicates that the traditional methods require an alternative when earthquake records are not available. The computation of broadband synthetic seismograms makes it possible, as required by a realistic modelling, to take source and propagation effects into account, fully utilizing the large amount of geological, geophysical and geotechnical data, already available. For recent earthquakes, where strong motion observations are available, it is possible to validate the modelling by comparing the synthetic seismograms with the experimental records. The realistic modelling of the seismic input has been applied to a first-order seismic zoning of the whole territory of several countries. Even though it falls in the domain of the deterministic approaches, the method is suitable to be used in new integrated procedures which combine probabilistic and deterministic approaches and allow us to minimize the present drawbacks which characterise them when they are considered separately. Detailed modelling of the ground motion for realistic heterogeneous media (up to 10 Hz) can be immediately used in the design of new seismo-resistant constructions and in the reinforcement of existing buildings, without having to wait for a strong earthquake to occur. The discrepancies between the ground responses computed with standard methods and the results of our detailed modelling cannot be ignored when formulating building codes and retrofitting the built environment.

The strong earthquake (M 6.0-6.2) that hit the central Apennines on August 24, 2016, occurred in one of the most seismically active areas in Italy. Field surveys indicated severe damage in the epicentral area where, in addition to the loss of human life, widespread destruction of cultural heritage and of critical buildings occurred. Using the neo-deterministic seismic hazard assessment (NDSHA), we apply the maximum deterministic seismic input (MDSI) procedure at two of the most relevant sites in the epicentral area, comparing the results with the current Italian building code. After performing an expeditious engineering analysis, we interpret as a possible cause of the reported damages the high seismic vulnerability of the built environment, combined with the source and site effects characterising the seismic input. Therefore, it is important to design and retrofit with appropriate spectral acceleration levels compatible with the possible future scenarios, like the ones provided by MDSI.

An effective strategy for the seismic risk mitigation needs the use of advanced seismological methodologies for a realistic estimate of the seismic hazard and, consequently, to reduce earthquake damage through a preventive evaluation of vulnerability and actions for structure safety. Prediction of earthquakes and their related effects (expressed in terms of ground shaking) can be performed either by a probabilistic approach or by using modelling tools based, on one hand, on the theoretical knowledge of the physics of the seismic source and of wave propagation and, on the other hand, on the rich database of geological, tectonic, historical information already available. Strong earthquakes are very rare phenomena and it is therefore statistically very difficult to assemble a representative database of recorded strong motion signals that could be analyzed to define ground motion parameters suitable for seismic hazard estimations. That is, the probabilistic estimation of the seismic hazard is a very gross approximation, and often a severe underestimation, of reality. A realistic and reliable estimate of the expected ground motion can be performed by using the Neo-Deterministic Seismic Hazard Analysis (NDSHA), an innovative modelling technique that takes into account source, propagation and local site effects (for a recent review see Panza et al., 2011). This is done using basic principles of physics about wave generation and propagation in complex media, and does not require to resort to convolutive approaches, that have been proven to be quite unreliable, mainly when dealing with complex geological structures, the most interesting from the practical point of view. The NDSHA approach has been used, among others, in the framework of the UNESCOIUGS-IGCP project 414 "Seismic Ground Motion in Large Urban Areas", to evaluate ground motion of a group of Large Urban Areas and Megacities in the world representative of a broad spectrum of seismic hazard severity (Panza et al., 2004). A MW 6.3 earthquake struck on 6 April 2009, at 01.32 GMT, the Abruzzo region (central Italy). The L’Aquila town, located few km northeast to the main shock epicentre, and several villages located nearby, suffered heavy damages and the casualties were about 300. The damage level generally corresponded to intensity ≤ VIII MCS, with few maximum values ≥

Estimates of seismic hazard obtained using the neo-deterministic approach (NDSHA) and the probabilistic approach (PSHA) are compared for the Italian territory. The NDSHA provides values larger than those given by the PSHA in areas where large earthquakes are observed and in areas identified as prone to large earthquakes, but lower values in low-seismicity areas. These differences suggest the adoption of the flexible, robust and physically sound NDSHA approach to overcome the proven shortcomings of PSHA, thus allowing for a reliable seismic hazard estimation, especially for those areas characterized by a prolonged quiescence, i.e. in tectonically active sites where events of only moderate size have occurred in historical times.

Kolkata, one of the oldest cities of India, is situated over the thick alluvium of the Bengal Basin, where it lies at the boundary of the zone III and zone IV of the seismic zonation map of India. An example of the study of site effects of the metropolitan Kolkata is presented based on theoretical modeling. Full synthetic strong motion waveforms have been computed using a hybrid method that combines the modal summation and finite difference techniques. The 1964 Calcutta earthquake, which was located at the southern part of Kolkata, is taken as the source region, with the focal mechanism parameters of dip = 32°, strike = 232° and rake = 56°. Four profiles are considered for the computation of the synthetic seismograms from which the maximum ground acceleration (AMAX) is obtained. Response spectra ratios (RSR) are then computed using a bedrock reference model to estimate local amplifications effects. The AMAX varies from 0.05 to 0.17 g and the comparison of the AMAX with the different intensity scales (MM, MSK, RF and MCS) shows that the expected intensity is in the range from VII to X (MCS) for an earthquake of magnitude 6.5 at an epicentral distance of about 100 km. This theoretical result matches with the empirical (historical and recent) intensity observations in Kolkata. The RSR, as a function of frequency, reaches the largest values (largest amplification) in the frequency range from 1.0 to 2.0 Hz. The largest site amplification is observed at the top of loose soil.

An integrated neo-deterministic approach to seismic hazard assessment has been developed that combines different pattern recognition techniques, designed for the space–time iden- tification of impending strong earthquakes, with algorithms for the realistic modeling of seismic ground motion. The integrated approach allows for a time-dependent definition of the seismic input, through the routine updating of earthquake predictions. The scenarios of expected ground motion, associated with the alarmed areas, are defined by means of full waveform modeling. A set of neo-deterministic scenarios of ground motion is defined at regional and local scales, thus providing a prioritization tool for timely preparedness and mitigation actions. Constraints about the space and time of occurrence of the impending strong earthquakes are provided by three formally defined and globally tested algorithms, which have been developed according to a pattern recognition scheme. Two algorithms, namely CN and M8, are routinely used for intermediate-term middle-range earthquake predictions, while a third algorithm allows for the identification of the areas prone to large events. These independent procedures have been combined to better constrain the alarmed area. The pattern recognition of earthquake-prone areas does not belong to the family of earthquake prediction algorithms since it does not provide any information about the time of occurrence of the expected earthquakes. Never- theless, it can be considered as the termless zero-approximation, which restrains the alerted areas (e.g. defined by CN or M8) to the more precise potential location of large events. Italy is the only region of moderate seismic activity where the two different pre- diction algorithms, CN and M8S (i.e. a spatially stabilized variant of M8), are applied simultaneously and a real-time test of predic- tions, for earthquakes with magnitude larger than a given threshold (namely 5.4 and 5.6 for CN algorithm, and 5.5 for M8S algorithm) has been ongoing since 2003. The application of the CN to the Adriatic region, which is relevant for seismic hazard assessment in the northeastern part of the Italian territory, is also discussed. Examples of neo-deterministic scenarios are provided, at regional and local scale and for the cities of Trieste and Nimis (Friuli Venezia Giulia region), where the knowledge of the local geological conditions permitted a detailed evaluation of the expected ground motion.

a r t i c l e i n f o A good knowledge of shear wave (V s ) structural models is required for the realistic modelling of seismic hazard scenarios. Nowadays there are many approaches based on surface wave dispersion evaluation, mainly oriented to the use of controlled source techniques with appropriate shot gathers. Subsoil deep controlled source surveys suffer great logistic problems and costs, due to the amount of source energy they need (e.g. explosive). Otherwise realistic seismic motion evaluation requires the knowledge of V s structural models even at large depths (e.g. 100-200 m). In this work we use the cross correlation of seismic noise in order to evaluate surface wave dispersion in a passive way, without controlled sources. Cross correlation of seismic noise recordings can be used to infer the impulse response between two points when the so-called noise correlation function (NCF) converges to the impulse response between two receivers,!ltered by the bandwidth of the noise spectrum. The NCF between two noise recording sensors could be in such a way considered as the passive analogous to a shot gather made with active sources in the space between the sensors themselves. In this work we computed the NCF between two sensors using both sea source noise and an anthropic noise source (an airport), in order to infer a V s structural model pro!le in an area of the Venice Plain (North-East Italy). Rayleigh wave fundamental mode dispersion curve has been extracted from NCF using the Frequency Time Analysis (FTAN) method. The results of the non-linear inversion of dispersion data, in terms of 1D V s distribution versus depth, are consistent with the geological subsoil conditions of the studied area and represent the!rst shear wave velocities middle deep characterisation of the Venetian hinterland.