Local Seismic Response Research Articles

Epistemic uncertainty in the seismic response of RC free-plan buildings

Complex building models consider multiple degrees of freedom and modeling assumptions that influence the accuracy of the predicted seismic response. This study evaluates the epistemic uncertainty inherent to modeling assumptions by evaluating the seismic response behavior of six instrumented reinforced concrete free-plan structures in Santiago, Chile. The free-plan structural concept is frequently used in office buildings and consists of a core of shear walls, a perimeter frame, and a flat slab connecting both lateral force resisting systems. Epistemic uncertainties studied in this paper are inherent to the following modeling assumptions: (1) the type of finite elements used in the building models; (2) the in-plane and out-of-plane stiffness of the diaphragms; (3) the interaction between the basement and the surrounding soil; and (4) the decision where to apply base fixity. The response uncertainty was first evaluated by comparing predicted and measured vibration periods using ambient vibrations and aftershock records of the 2010 Maule, Chile earthquake. Additionally predicted global and local seismic response parameters such as story shears, torques, and drifts were compared between a predefined reference model typically used in design and a set of variant models. A statistical evaluation of the modeling uncertainty showed a strong dependency on the response parameter considered. Larger uncertainties were observed for shear force related response parameters, including the influence of soil-structure interaction on base and story shears, while uncertainties for predicting fundamental periods or the depth at which building fixity was assumed had moderate impact on the overall building response. In general, uncertainties identified in core forces were larger than uncertainties in story forces and also larger at the underground stories than in comparison to upper levels.

SEISMIC MICROZONATION STUDIES CONSIDERING LOCAL SITE EFFECTS FOR YOGYAKARTA CITY, INDONESIA

An Mw 6.3 earthquake hit Yogyakarta, Indonesia in 2006, causing massive damage in this densely populated area. As a consequence, risk reduction efforts in terms of local seismic response and peak ground acceleration (PGA) mapping is needed to improve the spatial planning and early assessment beforeanother disastrous earthquake. The determination of PGA for microzonation study was conducted by referring to the Indonesian seismic code and empirical prediction by examining attenuation relationships considering the local site effects. The site investigation was conducted at 87 locations, comprising 13 core drillings and 74 microtremor measurements. Further, the nonlinear earthquake site response analyses were conducted to calculate the local seismic response occurring in a layered soil. Referring to the seismic codewith a 2% probability of exceedance in 50 years and site characteristics, the maximum considered earthquake geometric mean PGA for Yogyakarta City is 0.50-0.57g, while the southern area has higher PGA. The empirical prediction by attenuation relationships that considers the 6.3 Mw Yogyakarta earthquake 2006 with 50-100 year return period resulted in PGA of 0.14g to 0.21g. Meanwhile, the empirical prediction based on soil predominant period resulting from microtremor measurements shows that the southern part of the cityhas higher PGA of 0.2g to 0.3g whereas the northern part has lower PGA of 0.1g to 0.2g. The result of nonlinear earthquake site response analyses shows that the PGA at the southern part and the northern part of the city have higher PGA up to 0.38g. The results show the significance of local site effects and site response analysis in determining the earthquake characteristics in comparison to the present simplified empirical approach.

Comprehensive analysis of the local seismic response in the complex Büyükçekmece landslide area (Turkey) by engineering-geological and numerical modelling

Multi-risk management requires a strong comprehension of possible effects induced by natural hazardous events. In this regard, landslides triggering due to earthquakes results from complex interactions between seismic waves and slopes. Multidisciplinary approaches can significantly contribute to better understand such interactions. The large Büyükçekmece landslide (about 1500m wide and 1830m long) located in Turkey (Avcilar peninsula), about 15km northward from the North Anatolian Fault Zone (NAFZ), was selected as case-study in the framework of the European project “MARSite – Marmara Supersite: new directions in seismic hazard assessment through focused Earth observation in the Marmara Supersite”. The Avcilar area was recently affected by the 17th August 1999 Mw 7.4 Kocaeli and by the 12th November Mw 7.2 Düzce earthquakes. The Büyükçekmece landslide involves upper Oligocene to lower Miocene deposits, consisting of silty clays, tuffs and sands. No earthquake-induced re-activations are testified so far but the landslide area was interested by a very intense urbanization during the last decade. A detailed engineering-geological model for the local seismic response of the Büyükçekmece landslide slope was constructed based on geophysical measurements, data from a multisensor in-hole monitoring system and stress-strain numerical modelling. Several tens of earthquakes were recorded from October 2014 to May 2015 in the landslide site by considering in-hole and surface data. The reliability of the local seismic response obtained by numerical modelling respect to the empirically derived one was checked in terms of both site-to-reference spectral ratios and transfer function between surface and downhole sites inside the landslide mass. The 2D numerical amplification functions confirm that the local seismic response is a consequence of the complex geological setting of the landslide slope while no relevant amplification effects can be referred to topographic features. Based on these results, the interaction between seismic waves and the Büyükçekmece landslide slope cannot be neglected to evaluate the possibility of future landslide re-activations.

Local seismic response studies in the north-western portion of the August 24th, 2016 Mw 6.0 earthquake affected area. The case of Visso village (central Apennines)

In this work, we investigate the possible causes of the differential damaging observed in Visso village (central Apennines, about 28 km north from the August 24th, 2016 Mw 6.0 earthquake epicenter). Following insights from the available geological cartography at 1:10.000 scale, a preliminary geophysical survey has been performed in the damaged area in order to constrain geometries and extent of the subsoil lithotypes. Then, these results have been used to retrieve a Vs profile close to the most heavily damaged buildings. This latter has been used as input for a numerical analysis aimed at deriving the motion at the ground level in the study area. In particular, a linear equivalent simulation has been performed by means of EERA code and the waveform has been obtained convolving the time history recorded during the August 24th, 2016 mainshock at Spoleto Monteluco (SPM) site. Our preliminary results indicate a possible correlation of damaging to the thickness and shape of the geological units. Nevertheless, further analyses are necessary to highlight any 2D basin and / non - linear soil behaviour effects in order to compare them to the intrinsic buildings vulnerability, according to the EMS98 guidelines.

Down-hole geophysical characterization of middle-upper Quaternary sequences in the Apennine Foredeep, Mirabello, Italy

The 2012 earthquakes sequence stroke a wide area of the alluvial plain in the Emilia-Romagna Region and triggered a new research interest on the role of the subsurface stratigraphic architecture and petrophysical property distribution in the modulation of the local seismic effects. Few direct shear wave velocity V_S data were however available below the depth of 50m. The only available V_S measurements were obtained from an anticline area, characterized by a reduced stratigraphic thickness and peculiar sedimentary facies, hardly representative of the majority of the alluvial plain subsurface. The study provides the first V_S profile available from middle-upper Quaternary successions deposited into a fast subsiding syncline area of the Apennine Foredeep Basin. The P-wave velocity V_P and the S-wave velocity V_S logs fill in the previous data gap on the geophysical parameters needed for the estimation of the local seismic response. Both V_P and V_S logs were continuously acquired to the depth of 265 m. The log records a velocity increase with depth, punctuated by sharp increases at some stratigraphic discordance surfaces. The value of 800 m/s that characterizes the “seismic bedrock”, as defined by the Italian building code [NTC 2008] was never reached at any depth. The investigated succession records a depositional evolution from deltaic-marine to alluvial plain conditions, punctuated by six glacio-eustatic depositional cycles, developed in Middle-Upper Quaternary times. The stratigraphic units described in the syncline log were correlated at a regional scale, with the thinner anticline succession of Mirandola. Correlatable units deposited into syncline and anticline areas reveal similar shear wave velocity values, supporting the regional extrapolation of the measured values.<br /><br /><br /><em></em>

Fieldwork on local-site seismic response in the Po Plain: examples from ambient vibration array and single station analyses

In the framework of the S2 DPC-INGV 2014–2015 project (https://sites.google.com/site/ingvdpc2014progettos2/), several field surveys were designed with the aim to investigate the local seismic site response of selected Italian Accelerometric Network strong motion stations. In this study the results obtained at Sorbolo, Lesignano de’ Bagni, and Castelfranco Veneto, three sites located in the Po alluvial basin (northern Italy), were presented. In particular, at each site, ambient vibration surveys were performed both in single stations and two dimensional arrays configurations. The ambient vibration arrays were analyzed to obtain at each site the shear-wave velocity (Vs) profile, until depths in correspondence of which the Vs show values higher than 800 m/s (i.e. lower bound for the soil category A, as now defined in the Italian seismic code for building). In this way, data were processed through a joint inversion computed using both the Rayleigh waves dispersion curve and the ellipticity curve deduced from the horizontal-to-vertical spectral ratios calculated from the microtremor single station measurements. In general, the obtained profiles show an increasing depth of the main Vs discontinuity (i.e. the seismic bedrock) from 60 to 320 m, moving from the edge to the central part of the Po alluvial basin. To support the outcomes of the field experiments, the available earthquakes recorded at each station in the last decades were processed in terms of the horizontal-to-vertical spectral ratios. Although in many cases the resonance frequencies are comparable with those obtained from microtremor, a high variability is observable depending on the selected portions of each single earthquake. Finally, residual analysis were carried out comparing the recorded ground motion to predicted data as provided by the actual Italian ground motion prediction equations, calibrated both at national and at regional scale.

Surface geology and morphologic effects on seismic site response: The study case of Lampedusa, Italy

A joint Italo-Maltese research project (Costituzione di un Sistema Integrato di Protezione Civile Transfrontaliero Italo-Maltese, SIMIT) was financially supported by the European community with the aim to produce hazard maps in the area between the south-eastern Sicilian coast and the Sicily Channel including the islands of Lampedusa and Malta. In the frame of this project, the present study investigates the characteristics of the local seismic response in Lampedusa, a carbonate shelf belonging to the foreland domain at the northern edge of the African plate. Ninety-two ambient noise recordings were collected and processed through spectral ratio techniques. Polarization of the horizontal component of motion was also investigated in order to set into evidence possible directional effects. Results point out that in the central part of the island, where the most ancient and rigid terrains outcrop most of the spectral ratio plots show no particular site effects. On the other hand, nearby morphologic escarpments and fault lines, pronounced spectral ratio peaks in the frequency range 2.0–5.0 Hz are observed. These peaks, as highlighted by polarization analysis, are clearly directional with the largest amplification occurring with high angle (60°–90°) to the structures strike. Moreover, in sites located close to recent and soft deposits outcrops other significant seismic site effects at frequency higher than 5.0 Hz are identified. We can however assert that, rather than the surface lithology, the presence of cliff areas and tectonic structures strongly influence the local amplification of the ground motion and the occurrence of directional effects.

Exploratory seismic site response surveys in a complex geologic area: a case study from Mt. Etna volcano (southern Italy)

A preliminary study targeting to evaluate the local seismic response was performed in the eastern flank of Mt. Etna (southern Italy) using ambient noise measurements. The obtained spectral ratios were subdivided through cluster analysis into different classes of fundamental frequency permitting to draw an iso-frequency contour map. The analysis set into evidence the extreme heterogeneity of lava sequences, which makes difficult to identify a single seismic bedrock formation. Another important outcome, concerning the local seismic effects in terms of frequency and azimuth, is the important role played by the fracture fields associated with the main structural systems of the area. The existence of two zones with strong directional effects striking WNW–ESE and NW–SE, nearly orthogonal to the orientation of the main fracture fields, corroborate such hypothesis.

Seismic characterization and reconstruction of reference ground motion at accelerometric sites of the Italian national accelerometric network (RAN)

We present a field procedure that has been extensively used in Italy to characterize local seismic response at accelerometric sites and to retrieve ground motion at reference soil conditions by deconvolution analysis. To allow a generalized application to large areas where borehole data are generally lacking or inadequate for the seismic characterization for soils down to the reference seismic bedrock, cost-effectiveness of the considered procedures is a main issue. Thus, major efforts have been devoted to optimize available information and exploit fast and cheap surface geophysical prospecting. In particular, geological/geomorphological survey and passive seismic prospecting (both in single- and multi-station configurations) were jointly considered to reconstruct seismo-stratigraphical site conditions. This information was then used to feed numerical modeling aiming at computing the local seismic response and performing a deconvolution analysis to reconstruct ground motion at reference soil conditions. Major attention was devoted to evaluate and manage uncertainty involved in the procedure and to quantify its effect on final outcomes. An application of this procedure to a set of sites included in the Italian Accelerometric Network is presented.

Seismic response and vulnerability of historical Trakošćan Castle, Croatia using HVSR method

The Trakoscan Castle was built on the rocky peak of the hill in the thirteenth century. Castle structure has weakened with time, wars, inappropriate protection, and earthquakes. On 16 March 1982, the Tower Castle and part of second floor were damaged by an earthquake (M L = 4.5) with an epicenter 20 km distance from Mt. Ivancica. Afterwards, it was completely reconstructed. Today the cultural heritage of the Trakoscan Castle is protected as a historical entity by the Republic of Croatia. The Horizontal-to-Vertical-Spectral-Ratio (HVSR) method was applied for the purpose of local seismic response, protection from earthquake, structural seismic vulnerability of weak points, and structural restoration of the Trakoscan Castle related to the 1982 earthquake (microtremor measurements in free-field and in the Tower Castle). The free-field HVSR results (soil fundamental frequencies, amplification factors, shear wave velocity distribution, estimated bedrock depth, and directional effects on ground motion) are compared to the local geology, propagation path, and topographic effects to the estimated local seismic response. The dynamic behavior of the Tower Castle is demonstrated along different axes by the comparison of the directional HVSR analysis to the horizontal components (NS/V and EW/V) and the amplitude spectra (NS, EW and UD). The modal frequency response identifies weak points of the Tower Castle structure. Based on the HVSR analysis, the damage at Trakoscan site, related to the 1982 earthquake, occurred due to the local geology and topographic effects (seismic energy directed through the alluvial basin and trapped into the hill) and the improper way of the Tower Castle construction in the past and the reconstruction after the earthquake.

Influence of Lateral Heterogeneities on Strong‐Motion Shear Strains: Simulations in the Historical Center of Rome (Italy)

Abstract The influence of lateral heterogeneities on alluvial deposits is a topic of particular interest in the field of urban planning and engineering design of structures and infrastructures. This work focuses on the effects of such heterogeneities on the shear strains produced within the recent alluvial deposits of the Tiber River in the historical center of Rome in case of the worst expected earthquake scenario. To this aim, a 3D engineering‐geology model of the subsoil is used to derive four geological sections across the Tiber River valley as well as 48 soil columns to perform numerical simulations. Various models are considered: a viscoelastic equivalent linear rheology in a 1D finite‐difference model for one‐component horizontal input, a nonlinear elastoplastic model in a 1D finite‐element scheme for three‐component input, and a nonlinear viscoelasto‐plastic rheology in a 2D finite‐difference model under one‐component horizontal input. After comparing these different simulations, results have shown that lateral heterogeneities play a key role with respect to the expected shear strains within multilayered soils. To this aim, some specific indexes are introduced to estimate the maximum shear strain (MSS) concentration within the soil layers as well as to highlight their effect due to the stratigraphic position of the layers, within the soil column, independently from its depth. A final differential index leads to the evaluation of the lateral heterogeneity effect on the estimated MSS, demonstrating their prevalent role with respect to the bedrock shape (i.e., the angle of inclination of the buried valley slopes). From these results, an MSS zoning map is obtained for the historical center of Rome, showing that the local seismic response should be modeled by assuming 1D or 2D conditions depending on the location considered.

The local seismic response of the Fosso di Vallerano valley (Rome, Italy) based on a high-resolution geological model

The main purpose of this study is the analysis of the local seismic response in the Fosso di Vallerano valley, an alluvial basin located in a recently urbanized area of Rome (Italy). A high-resolution geological model was obtained starting from 250 available borehole log stratigraphies and pressiometer in-site tests; the model highlighted a complex and heterogeneous setting of both the local substratum and the alluvial fill. The local seismo-stratigraphy was derived based on several noise measurements as well as one cross-hole test. A preliminary validation of the stratigraphic model was performed by modeling the amplification functions (SSR) derived from weak motions recorded on August 2009 through a temporary velocimetric array. The obtained results show that the recent alluvial deposits have one principal mode of vibration at about 0.8 Hz and different secondary vibrational modes due to the characteristic stratigraphic setting of the alluvia. The seismic bedrock can be located within the Paleo Tiber 4 deposits (Santa Cecilia Formation) by assuming a velocity gradient in these deposits (i.e. corresponding to the Vs increment from about 500 m/s up to 1100 m/s).

Real-time assessment framework of spatial liquefaction hazard in port areas considering site-specific seismic response

This paper proposes a systematic framework for real-time assessment of spatial liquefaction hazard of port areas considering local seismic response characteristics based on a geographic information system (GIS) platform. The framework is integrated and embedded with sequential, interrelated subprocedures and a database for liquefaction-induced damage evaluation that standardizes and both individually and collectively quantifies analytical results. To integrate the current in situ condition of a selected port area, the framework functions as a spatial database system for geotechnical and structural data and as a recipient of automatic transmission of seismic monitoring data. The geotechnical profile correlated with liquefaction potential is compiled into a geotechnical spatial grid built by geostatistical methods. Linked with the geotechnical spatial grid, the processing of site-specific responses is automatically interpreted from previously derived correlations between rock acceleration and maximum acceleration of each soil layer. As a result, the liquefaction severity is determined based on a combined geotechnical spatial grid with seismic load correlation in real-time according to a simplified procedure, allowing calculation of the liquefaction potential index (LPI). To demonstrate practical applications of the framework in estimating the liquefaction hazard in real-time, liquefaction-hazard maps were visualized for two earthquake scenarios, verifying the applicability of the proposed framework.

The role of site effects in the comparison between code provisions and the near field strong motion of the Emilia 2012 earthquakes

A damaging seismic sequence hit a wide area mainly located in the Emilia-Romagna region (Northern Italy) during 2012 with several events of local magnitude $$\hbox {M}_\mathrm{l} \ge 5$$ , among which the $$\hbox {M}_\mathrm{l}$$ 5.9 May 20 and the $$\hbox {M}_\mathrm{l}$$ 5.8 May 29 were the main events. Thanks to the presence of a permanent accelerometric station very close to the epicentre and to the temporary installations performed in the aftermath of the first shock, a large number of strong motion recordings are available, on the basis of which, we compared the recorded signals with the values provided by the current Italian seismic regulations, and we observed several differences with respect to horizontal components when the simplified approach for site conditions (based on Vs30 classes) is used. On the contrary, when using the more accurate approach based on the local seismic response, we generally obtain a much better agreement, at least in the frequency range corresponding to a quarter wavelength comparable with the depth of the available subsoil data. Some unresolved questions still remain, such as the low frequency behaviour ( $$<$$ 1 Hz) that could be due either to complex propagation at depth larger than the one presently investigated or to near source effects, and the behaviour of vertical spectra whose recorded/code difference is too large to be explained with the information currently available.

The seismic microzonation of level 3 of Sant’Agata Fossili (northern Italy) based on a multidisciplinary approach

&lt;p&gt;In this paper the results of a detailed seismic microzonation, performed at Sant’Agata Fossili (Piemonte region, northern Italy) are presented. We study the local seismic response of this small village using a level 3, that is the most accurate level following the Italian code of seismic microzonation. The activity steps consist in a gradual widening of knowledge of the different aspects of the amplification phenomena. A multidisciplinary approach has been performed to obtain the local seismic response: including a study of local geology, geophysical and geotechnical characterization of the lithologies, and numerical and experimental analyses. We finally compare the obtained elastic response spectra to the prescribed spectra of the Italian Building Code (in Italian: Norme Tecniche per le Costruzioni). Our results show the geologic and geophysical differences of the subsoil, that produce different local seismic response in terms of amplification factors and acceleration response spectra.&lt;/p&gt;

A physical stratigraphy model for seismic microzonation of the Central Archaeological Area of Rome (Italy)

A reliable litho-technical model for seismic microzonation requires a robust understanding of the subsoil architecture, that is essential to extrapolate in the space geognostic data that are often sparse. This paper presents the application to the level 1 seismic microzonation of the Central Archaeological Area of Rome of a complete methodological approach implementing physical stratigraphy concepts into an integrated analysis of a subsurface dataset. Particular emphasis has been placed on the reconstruction of buried geometries, distribution of lithofacies, and stacking pattern of geological bodies, which can control local seismic response. The spatial distribution of paleovalley infill and interfluves domains in the subsoil was reconstructed, which in virtue of their peculiar stratigraphy and morphology may determine 1D and 2D resonance effects. The summation of amplification effects due to the thick anthropogenic layer allowed to outline five stable zones prone to ground motion amplification, of which the most critical coincide with the narrow and deep infill of recent valleys. Potentially less prone to valley effects is the Middle Pleistocene paleovalley infill in the subsurface of the northern and eastern Palatine hill. Finally, the less hazardous zones correspond to the ancient, multilayered volcano-sedimentary interfluves separating the paleovalleys.

Influence of epicentral distance on local seismic response in Kolkata City, India

The influence of source and epicentral distance on the local seismic response in the Kolkata city is investigated by computing the seismic ground motion along 2-D geological cross-sections in the Kolkata city for the earthquake that occurred on 12 June 1897 (M w = 8.1; focal mechanism: dip = 57°, strike = 110° and rake = 76°; focal depth = 9 km) in Shillong plateau. For the estimation of ground motion parameters, a hybrid technique is used, which is the combination of modal summation and finite difference method. This technique allows the estimation of site specific ground motion for various events located at different distances from Kolkata city, taking into account simultaneously the position and geometry of the seismic source, the mechanical properties of the propagation medium and the geotechnical properties of the site. The epicenter of the Shillong earthquake is about 460 km away from Kolkata. The estimated peak ground acceleration (PGA) varies in the range of 0.11–0.18 g and this range corresponds to the intensity of IX to X on the Mercalli-Cancani-Sieberg (MCS) scale and VIII on the Modified Mercalli (MM) scale. The maximum amplification in terms of response spectral ratio (RSR) varies from 10 to 12 in the frequency range 1.0–1.5 Hz. These amplifications occur in correspondence to low-velocity shallow, loose soil deposit. The comparison of these results with earlier ones obtained considering the Calcutta earthquake that occurred on 15 April 1964 (M w = 6.5; focal mechanism: dip = 32°, strike = 232° and rake = 56°; focal depth = 36 km) shows that the source parameters (magnitude and focal mechanism) and epicentral distance play an important role on site response but the variation in the frequency of the peak values (RSR) is negligible. The obtained results match with observed reported intensities in Kolkata region.

The role of near-field interaction between seismic waves and slope on the triggering of a rockslide at Lorca (SE Spain)

Abstract. A ~1000 m3 rockslide occurred close to Lorca (SE Spain) during the main shock (Mw = 5.1) of the May 2011 seismic sequence. The location of the rockslide, within 10 km of the earthquake epicenter and along the southern slope of a valley in which similar geological conditions occur on both slopes of the valley, suggests a significant near-field effect due to local seismic response. This could be related to the specific interaction between the topography and the obliquely propagating seismic waves. A dynamic stress strain numerical model was constructed using the FLAC 7.0 finite difference code to back analyze the Lorca rockslide event and relate its occurrence to both the local seismic amplification and the interaction between seismic waves and local topography. The results indicate that only for seismic waves with incidence angles in the range 0°–50° are the occurred slope instabilities expected. These results do not significantly change when varying the values for either stiffness or strength parameters within the range of the experimental data.

Seismic property characterization of lithotypes cropping out in the Siracusa urban area, Italy

The town of Siracusa is located in the south-eastern coast of Sicily (southern Italy) in a wide inlet engraved into a limestone formation. This lithotype, which is overlaid by soft sediments such as sandy clays and detritus, can be considered as the local bedrock. Present study aims to investigate on the dynamic properties of main lithotypes outcropping in the study area and their relationships with the local seismic response. Non-invasive seismic prospecting techniques using the vertical component of surface waves (MASW and ReMi) were adopted, as well as ambient noise measurements, processed through the Nakamura technique. The best solution for the experimental dispersion curves was selected using the neighbourhood algorithm and information about the deeper part of the estimated shear wave profiles was obtained by considering the ellipticity of the fundamental peak. Moreover, a cluster analysis was performed to subdivide into homogeneous groups the experimental noise spectral ratios. Results obtained pointed out that the use of combined different methods provides a robust way to characterize the investigated soils and to reduce the problems linked to the non-uniqueness of solutions during the interpretation of geophysical data.

A grade-3 method of zonation for seismic slope stability: An Italian case study

This paper presents a seismic microzonation study performed in an area of the Northern Apennines (Italy) in order to reduce the level of risk from landslide hazard, to support decisions in urban planning and to provide useful information for building design. The area in question measures about 2.6km2 and is characterised by considerable landslide susceptibility also in non seismic conditions as evidenced by a number of surveys carried out over the past years. The slope deposit, lying over a marley-arenaceous formation, shows a variable thickness from a few metres to 30m and consists of fine silty-clay, clay-sandy and silty-sandy soil in a variable amount. Quiescent and active landslide areas with ground movements involving the shallowest layers of the soil deposit have been detected.Given the relatively high seismicity of the region, the aim of this study is to describe the principles and criteria adopted in a seismic risk analysis conducted over a limited area in order to carry out a very high and detailed level of zonation for ground motion and slope stability (i.e., Grade 3 according to the definition in the Manual for Zonation on Seismic Geotechnical Hazards). For this purpose, reliable expected earthquakes were assumed and in-depth geologic, geomorphologic, geotechnical and geophysical analyses were carried out to define a subsoil model for performing numerical analyses of local seismic response and slope stability in both non-seismic and seismic conditions. The proposed methodology consists of the following three steps: (i) identification of a number of seismic inputs for the numerical analyses; (ii) implementation of numerical analyses to evaluate the amplification of ground shaking and to assess potential for slope failure; (iii) mapping of homogeneous areas with respect to expected site amplifications and landslide risk. The study allowed the mapping of four zones which are expected to be homogeneous in terms of both amplification factor of seismic motion (FA) and safety factor against landslide (FS). Quiescent and active landslide zones were thus identified with greater accuracy together with the most probable sliding surfaces. For this purpose, a 1-D numerical code was adopted for seismic response analyses and limit equilibrium methods were implemented and numerically solved in static and pseudo-static slope stability analyses.