This study evaluates the seismically induced displacements of a slope using the Finite Element Method (FEM) in comparison to the results of twelve empirical predictive approaches. First, the existing methods to analyze the stability of slopes subjected to seismic loads are presented and their capabilities to predict the onset of failure and post-failure behavior are discussed. These methods include the pseudostatic method, the Newmark method, and stress-deformation numerical methods. Whereas the pseudostatic method defines a seismic coefficient for the analysis and provides a safety factor, the Newmark method incorporates a yield coefficient and the actual acceleration time history to estimate permanent displacements. Numerical methods incorporate advanced constitutive models to simulate the coupled stress-strain soil behavior, making the process computationally more costly. In this study, a model slope previously studied at laboratory scale is selected and scaled up to prototype dimensions. Then, the slope is subjected to 88 different input motions, and the seismic displacements obtained from the numerical and empirical approaches are compared statistically. From correlation analyses between seven ground motion parameters and the numerical results, new empirical predictive equations are developed for slope displacements. The results show that overall the FEM displacements are generally in agreement with the numerically developed methods by Fotopoulou and Pitilakis (2015) labelled "Method 2" and "Method 3", and the Newmark-type Makdisi and Seed (1978) and Bray and Travasarou (2007) methods for rigid slopes. Finally, functional forms for seismic slope displacement are proposed as a function of peak ground acceleration (PGA), Arias intensity (Ia), and yield acceleration ratio (Ay/PGA). These functions are expected to be valid for granular slopes such as earth dams, embankments, or landfills built on a rigid base and with low fundamental periods (Ts<0.2). / Master of Science / A landslide is a displacement on a sloped ground that can be triggered by earthquake shaking. Several authors have investigated the failure mechanisms that lead to landslide initiation and subsequent mass displacement and proposed methodologies to assess the stability of slopes subjected to seismic loads. The development of these methodologies has to rely on field data that in most of the cases are difficult to obtain because identifying the location of future earthquakes involves too many uncertainties to justify investments in field instrumentation (Kutter, 1995). Nevertheless, the use of scale models and numerical techniques have helped in the investigation of these geotechnical hazards and has led to development of equations that predict seismic displacements as function of different ground motion parameters. In this study, the capabilities and limitations of the most recognized approaches to assess seismic slope stability are reviewed and explained. In addition, a previous shaking-table model is used for reference and scaled up to realistic proportions to calculate its seismic displacement using different methods, including a Finite Element model in the commercial software Plaxis2D. These displacements are compared statistically and used to develop new predictive equations. This study is relevant to understand the capabilities of newer numerical approaches in comparison to classical empirical methods.

The KiK-net ground motion database is used to develop ground motion prediction equations for Arias Intensity (I_a), 5-95% Significant Duration (Ds_5-95), and 5-75% Significant Duration (Ds_5-75). Relationships are developed both for shallow crustal earthquakes and subduction zone earthquakes (hypocentral depth less than 45 km). The models developed consider site amplification using V_S30 and the depth to a layer with V_S=800 m/s (h₈₀₀). We observe that the site effect for I_α is magnitude dependent. For Ds_5-95 and Ds_5-75, we also observe strong magnitude dependency in distance attenuation. We compare the results with previous GMPEs for Japanese earthquakes and observe that the relationships are similar. The results of this study also allow a comparison between earthquakes in shallow-crustal regions, and subduction regions. This comparison shows that Arias Intensity has similar magnitude and distance scaling between both regions and generally Arias Intensity of shallow crustal motions are higher than subduction motions. On the other hand, the duration of shallow crustal motions are longer than subduction earthquakes except for records with large distance and small magnitude causative earthquakes. Because small shallow crustal events saturate with distance, ground motions with large distances and small magnitudes have shorter duration for shallow crustal events than subduction earthquakes.

Properly accounting for the uncertainties in predicting ground motion parameters is critical for Probabilistic Seismic Hazard Analyses (PSHA). This is particularly important for critical facilities that are designed for long return period motions. Non-ergodic PSHA is a framework that allows for this proper accounting of uncertainties. This, in turn, allows for more informed decisions by designers, owners and regulating agencies. The ergodic assumption implies that the standard deviation applicable to a specific source-path-site combination is equal to the standard deviation estimated using a database with multiple source-path-site combinations. The removal of the ergodic assumption requires dense instrumental networks operating in seismically active zones so that a sufficient number of recordings are made. Only recently, with the advent of networks such as the Japanese KiK-net network has this become possible. This study contributes to the state of the art in earthquake engineering and engineering seismology in general and in non-ergodic seismic hazard analysis in particular. The study is divided in for parts. First, an automated protocol was developed and implemented to process a large database of strong ground motions for GMPE development. A comparison was conducted between the common records in the database processed within this study and other studies. The comparison showed the viability of using the automated algorithm to process strong ground motions. On the other hand, the automated algorithm resulted in narrower usable frequency bandwidths because of the strict criteria adopted for processing the data. Second, an approach to include path-specific attenuation rates in GMPEs was proposed. This approach was applied to a subset of the KiK-net database. The attenuation rates across regions that contains volcanoes was found to be higher than other regions which is in line with the observations of other researchers. Moreover, accounting for the path-specific attenuation rates reduced the aleatoric variability associated with predicting pseudo-spectral accelerations. Third, two GMPEs were developed for active crustal earthquakes in Japan. The two GMPEs followed the ergodic and site-specific formulations, respectively. Finally, a comprehensive residual analysis was conducted to find potential biases in the residuals and propose models to predict some components of variability as a function of some input parameters. / Ph. D.

Ground motions from earthquakes are known to be affected by earth's surface topography. Topographic effects are a result of several physical phenomena such as the focusing or defocusing of seismic waves reflected from a topographic feature and the interference between direct and diffracted seismic waves. This typically causes an amplification of ground motion on convex features such as hills and ridges and a de-amplification on concave features such as valleys and canyons. Topographic effects are known to be frequency dependent and the spectral accelerations can sometimes reach high values causing significant damages to the structures located on the feature. Topographically correlated damage pattern have been observed in several earthquakes and topographic amplifications have also been observed in several recorded ground motions. This phenomenon has also been extensively studied through numerical analyses. Even though different studies agree on the nature of topographic effects, quantifying these effects have been challenging. The current literature has no consensus on how to predict topographic effects at a site. With population centers growing around regions of high seismicity and prominent topographic relief, such as California, and Japan, the quantitative estimation of the effects have become very important. In this dissertation, we address this shortcoming by developing empirical models that predict topographic effects at a site. These models are developed through an extensive empirical study of recorded ground motions from two large strong-motion datasets namely the California small to medium magnitude earthquake dataset and the global NGA-West2 datasets, and propose topographic modification factors that quantify expected amplification or deamplification at a site. To develop these models, we required a parameterization of topography. We developed two types of topographic parameters at each recording stations. The first type of parameter is developed using the elevation data around the stations, and comprise of parameters such as smoothed slope, smoothed curvature, and relative elevation. The second type of parameter is developed using a series of simplistic 2D numerical analysis. These numerical analyses compute an estimate of expected 2D topographic amplification of a simple wave at a site in several different directions. These 2D amplifications are used to develop a family of parameters at each site. We study the trends in the ground motion model residuals with respect to these topographic parameters to determine if the parameters can capture topographic effects in the recorded data. We use statistical tests to determine if the trends are significant, and perform mixed effects regression on the residuals to develop functional forms that can be used to predict topographic effect at a site. Finally, we compare the two types of parameters, and their topographic predictive power. / Ph. D.

L'objectif de cette thèse vise à améliorer la définition des vibrations (« mouvement sismique ») sur des sites « durs » (sédiments raides ou rochers) liés à des scénarios (séismes de magnitude entre 5 et 6.5, distances inférieures à 50 kilomètres) représentatifs du contexte métropolitain français. Afin de contraindre ces mouvements sismiques sur sites « durs », une base de données accélérométriques a été construite, à partir des enregistrements accélérométriques japonais K-NET et KiK-net qui ont l'avantage d'être publiques, nombreux et de grande qualité. Un modèle de prédiction des mouvements sismiques (spectre de réponse en accélération) a été conçu à partir de cette nouvelle base. La comparaison entre modèles théoriques et observations montre la dépendance des vibrations sur sites rocheux à la fois aux caractéristiques de vitesse du site (paramètre classique décrivant la vitesse des ondes S dans les 30 derniers mètres) et aux mécanismes d'atténuation hautes fréquences (un phénomène très peu étudié jusque-là). Ces résultats confirment une corrélation entre ces deux mécanismes (les sites rocheux les plus mous atténuent plus le mouvement sismique à hautes fréquences) et nous proposons un modèle de prédiction du mouvement sismique prenant en compte l'ensemble des propriétés du site (atténuation et vitesse). Les méthodes nouvelles de dimensionnement dynamiques non linéaires (à la fois géotechniques et structurelles) ne se satisfont pas des spectres de réponse mais requièrent des traces temporelles. Dans le but de générer de telles traces temporelles, la méthode stochastique non stationnaire développée antérieurement par Pousse et al. 2006 a été revisitée. Cette méthode semi-empirique nécessite de définir au préalable les distributions des indicateurs clés du mouvement sismique. Nous avons ainsi développé des modèles de prédiction empiriques pour la durée de phase forte, l'intensité d'Arias et la fréquence centrale, paramètre décrivant la variation du contenu fréquentiel au cours du temps. Les nouveaux développements de la méthode stochastique permettent de reproduire des traces temporelles sur une large bande de fréquences (0.1-50 Hz), de reproduire la non stationnarité en temps et en fréquence et la variabilité naturelle des vibrations sismiques. Cette méthode présente l'avantage d'être simple, rapide d'exécution et de considérer les bases théoriques de la sismologie (source de Brune, une enveloppe temporelle réaliste, non stationnarité et variabilité du mouvement sismique). Dans les études de génie parasismique, un nombre réduit de traces temporelles est sélectionné, et nous analysons dans une dernière partie l'impact de cette sélection sur la conservation de la variabilité naturelle des mouvements sismiques. / The aim of this thesis is to improve the definition of vibrations ("seismic motion") on "hard" sites (hard soils or rocks) related to scenarios (earthquakes of magnitude between 5 and 6.5, distances less than 50 km) representative of the French metropolitan context.In order to constrain the seismic motions on "hard" sites, an accelerometric database was built, from the K-NET and KiK-net Japanese recordings which have the benefit of being public, numerous and high quality. A ground motion prediction equation for the acceleration response spectra was developed from this new database. The comparison between theoretical models and observations shows the dependence of vibration on rock sites in both the velocity characteristics of the site (classical parameter describing the S-wave velocity in the last 30 meters) and the high frequency attenuation mechanisms (a phenomenon little studied up to now). These results confirm a correlation between these two mechanisms (the high frequency seismic motion is more attenuated in the case of softer rock sites) and we propose a ground motion prediction equation taking into account all the properties of the site (attenuation and velocity).New methods of nonlinear dynamic analysis (both geotechnical and structural) are not satisfied with the response spectra but require time histories. To generate such time histories, the non-stationary stochastic method previously developed by Pousse et al. (2006) has been revisited. This semi-empirical method requires first to define the distributions of key indicators of seismic motion. We have developed empirical models for predicting the duration, the Arias intensity and the central frequency, parameter describing the frequency content variation over time. New developments of the stochastic method allow to reproduce time histories over a wide frequency band (0.1-50 Hz), to reproduce the non-stationarity in time and frequency and to reproduce the natural variability of seismic vibrations. This method has the advantage of being simple, fast and taking into account basic concepts of seismology (Brune's source, a realistic envelope function, non-stationarity and variability of seismic motion). In earthquake engineering studies, a small number of time histories is selected, and we analyze in the last part the impact of this selection on the conservation of the ground motion natural variability.