Towards a uniform earthquake risk model for Europe

Seismic risk has been the focus of a number of European projects in recent years, but there has never been a concerted effort amongst the research community to produce a uniform European risk model. The H2020 SERA project has a work package that is dedicated to that objective, with the aim being to produce an exposure model, a set of fragility/vulnerability functions, and socio-economic indicators in order to assess probabilistic seismic risk at a European scale. The partners of the project are working together with the wider seismic risk community through web tools, questionnaires, workshops, and meetings. All of the products of the project will be openly shared with the community on both the OpenQuake platform of the Global Earthquake Model (GEM) and the web platform of the European Facilities for Earthquake Hazard and Risk (EFEHR)

Remote sensing vs. field survey data in a post-earthquake context: Potentialities and limits of damaged building assessment datasets

International audienceQuick building damage assessment following disasters such as large earthquakes serves to establish a preliminary estimation of losses and casualties. These datasets are completed by employing several crowdsourcing initiatives, in which volunteers and collaborators map damaged buildings in a given area at a qualitative damage scale based on a post-earthquake aerial or satellite image. Automating this process is a temptation and a technical issue, but manual interpretation remains essential, with the identification of moderate and lateral damage being the key and limiting factor. Following the Haiti 2010 earthquake, many studies were completed by crossing multilayer data gathered from different sources (satellite, aerial, and field survey). These works created a building damage dataset that enabled the construction of different sets of empirical vulnerability functions. In the present study, we proposed to review the datasets used for the damage assessment again, investigate how they can be managed for understanding urban damage patterns, and quantify the potentialities and limits of the sets. A high-resolution map of damage in Port-au-Prince was used to obtain a deducted map of intensity and was then compared to more detailed post-earthquake investigations such as the microzonation of the city (Belvaux et al., 2018). These detailed post-earthquake investigations, in which array microtremor measurements are performed for characterization of the subsurface soil, contribute to a better understanding of local variations in intensity. Subsequently, a retro damage scenario was run, considering the different sets of vulnerability functions (using the RISK-UE methodology vulnerability indexes) fitted with empirical vulnerability functions. Using the characterization of the exposure on a remote sensing basis, the results fit the heaviest damage well (building collapse), but they overestimated moderate damage states compared to the observations. However, is an aerial image based dataset sufficiently exhaustive for moderate damage, which is mostly visible from a lateral or internal point of view? Finally, we suggested some range of adjustments that can be applied to a vulnerability assessment originating from remote sensing data such that it can be used more accurately in the detection of urban damage, even for moderate damage degrees

Comparisons between SHARE and current national seismic hazard maps for France

International audienceThe EU‐FP7 project SHARE has recently delivered the first complete harmonized model characterizing the seismic hazard and its uncertainty in Europe. For the purpose of EN 1998, national territories are subdivided by the National Authorities into seismic zones depending on the seismic hazard level. The paper presents and discusses some of the SHARE results with respect to the seismic hazard map that is the basis of the French seismic design code. It highlights several issues for improving the French seismic zonation, as well as some criticisms of the SHARE model for France

Intégration de données géophysiques dans la réalisation de microzonages

International audienceLors d’études récentes de microzonage sismique, le BRGM a utilisé deux méthodes géophysiques dans l’objectif de mieux contraindre les données géologiques et de suppléer au manque de sondages géotechniques. La technique H/V bruit de fond et la méthode SASW sont théoriquement complémentaires : La méthode H/V doit donner la fréquence de résonance du sol, reliée à l’épaisseur des couches et à la vitesse des ondes de cisaillement dans ces couches, paramètres qui peuvent être estimés par la méthode SASW. Cependant, leur mise en application, même si elle a apporté une aide très significative pour la réalisation des microzonages, a également soulevé beaucoup de questions. A partir de quelques exemples, nous proposons de montrer les apports réciproques de ces deux méthodes au travers de la réalisation de ces microzonages

Étude de sensibilité sur le modèle PSHA de SHARE et exploration des incertitudes liées aux modèles de sismicité – application à la France

International audienceSUMMARY. In 2013, the SHARE project delivered a harmonized model characterizing the seismic hazard in the entire Euro-Mediterranean region. This study is led within the framework of an adhoc AFPS working group discussing the SHARE assumptions, methodologies and results for France.TheSHARE earthquake recurrence models for France rely greatly on expert opinion. A sensitivity study on some input model parametersis performed (minimum and maximum magnitudes contributing to the hazard). The impact of the fault model on the hazard is studied. Some errors in the input files are identified, a corrected hazard map is produced. In an attempt to account for the uncertainties on the source model, new recurrence curves with associated uncertainties are derivedbased on SHARE's earthquake catalog (SHEEC). The recently published SI-Hex catalog, anew unified instrumental catalog for France (Cara et al., 2015) is also used to derive alternative recurrence curves. Based on these new source models, alternativePSH estimates are obtained for France.The results show that the uncertainty on the recurrence parameters in France is large and that the impact on hazard can be so large that it should not be neglected.Le projet SHARE a produit fin 2013 des cartesharmonisées de l'aléasismique pour l'ensemble de la région euro-méditerranéenne. La présenteétudeestmenéedans le cadre d'un groupe de travail de l'AFPSayant pour objectifd'analyser les méthodesproposéesdans SHARE et les résultats pour la France. Les modèles de SHARE, pour la France, reposentfortementsur des critèresd'expert. La sensibilité des résultats au choixdes magnitudes minimalesetmaximalesestquantifiée. Le modèleintégrant les faillesestanalysé et son impact surl'aléaestquantifié. Des erreursdans les fichiersd'entréesontidentifiées, etune carte corrigéeestproduite. Afin de quantifier les incertitudessur le modèle de source, nous avonsrepris le catalogue de sismicité de SHARE (SHEEC), etavonsétabli des courbes de récurrence avec incertitude. Enparallèle, le SI-Hex catalogue de sismicitéunifiéethomogènerécemmentpublié par Cara et al. (2015) a étéexploité pour fournir des modèles de récurrencealternatifs. Les estimations d'aléasismiqueprobabilistebaséessurcesdifférentsmodèles de sources montrentquel'impactsurl'aléaest important. Plus d'attentiondevraitêtreapportée aux modèles de source et à la quantification des incertitudes qui les caractérisent

Combined Geophysical and Geotechnical Approaches for Microzonation Studies in Hispaniola Island

In this paper, we describe recent studies for the geophysical and geomechanical characterization of soils in Hispaniola (Greater Antilles), an island threatened by the eventual rupture of major seismogenic fault systems. The investigations were performed for four different cities settled on complex geological formations in Haiti (Cap-Haïtien, Port-au-Prince) and the Dominican Republic (Santo Domingo, Santiago de los Caballeros). We present the complete methodology we implemented for mapping zones of homogeneous seismic response and for microzonation studies, but each main stage of investigation is described as it was conducted in one or two cities. Therefore, first we present our site-characterization technique applied to Santo Domingo and Santiago de los Caballeros, which is based on geotechnical data, geophysical multichannel analysis of surface waves, and ambient-noise recordings. Then we present the site-response analysis through numerical analysis with nonlinear soil models that we performed for the city of Cap-Haïtien. Finally, we describe the amplification factors for site-specific response spectra that we derived for the microzonation of Port-au-Prince. We argue for the implementation of a multidisciplinary approach built upon complementary field geological, geophysical, and geotechnical data rather than solely depending on geophysical measures for the characterization of VS30. In addition, we explore the compatibility of the soil classes recommended by the International Building Code (IBC) in the context of local seismic amplification

Geology of Santiago de los Caballeros, Dominican Republic, applied to seismic microzoning study

Tras el terremoto de Haití de 2010 dio comienzo una iniciativa para estudiar los posibles efectos de los terremotos en la ciudad de Santiago de los Caballeros (República Dominicana); la segunda ciudad más importante del país y que ya fue reconstruida y reubicada en 1562. El daño debido a un terremoto ocurre asociado a un conjunto de factores, entre ellos, la aceleración del suelo. El efecto de la atenuación de la distancia en un radio de unos pocos kilómetros suele ser mucho menos relevante que el efecto de la variación en las propiedades de los suelos. Este artículo recoge los resultados obtenidos de los estudios de peligro sísmico y microzonificación sísmica en la ciudad de Santiago de los Caballeros: i) cuantificación del peligro sísmico regional debido a la falla septentrional; ii) un nuevo mapa geológico y iii) la cartografía de zonas de respuesta sísmica homogénea y susceptibilidad a la licuefacción.After the Haiti quake of 2010 an initiative started to better understand shaking effects in the city of Santiago de los Caballeros (Dominican Republic); a city that was devastated after an earthquake and rebuilt in a new site in 1562. It is well known that damage because of an earthquake occurs associated to a number of factors, ground acceleration is amid them. Within the range of a few kilometers, the effect of distance attenuation might be far less relevant than the effect of varying properties of soils. This paper gathers results obtained from the seismic hazard and microzonation studies developed in the city of Santiago: i) quantification of regional seismic hazard dominated by the Septentrional fault, ii) a new geological mapping of superficial formations, and iii) mapping of zones of homogeneous seismic response and liquefaction susceptibili

Geología para el estudio de microzonación sísmica en Santiago de los Caballeros, República Dominicana.

p. 715-736Tras el terremoto de Haití de 2010 dio comienzo una iniciativa para tratar de entender mejor los efectos de los terremotos en la República Dominicana, en particular en la ciudad de Santiago de los Caballeros, segunda más importante del país. Santiago ha sufrido varios terremotos devastadores, en 1562 la ciudad fue reconstruida en un nuevo sitio al sur de la falla responsable. El daño debido a un terremoto ocurre asociado a un conjunto de factores, entre ellos, la aceleración del suelo, que por lo general se señala como el principal o como la clave para explicar la mayor parte de los efectos. La aceleración del suelo varía dependiendo principalmente de la distancia al epicentro, de las propiedades del suelo y de la topografía. En cuanto a la distancia, es de esperar menor aceleración conforme aumenta la distancia al epicentro. De otra parte, suelos con diferentes características dan lugar a diferentes respuestas. Los efectos de la topografía aún no se comprenden bien. El efecto de la atenuación de la distancia en un radio de unos pocos kilómetros suele ser mucho menos relevante que el efecto de la variación en las propiedades de los suelos. Este artículo recoge los resultados obtenidos de los estudios de peligro sísmico y microzonificación sísmica en la ciudad de Santiago de los Caballeros: i) cuantificación del peligro sísmico regional debido a la falla septentrional; ii) un nuevo mapa geológico y iii) la cartografía de zonas de respuesta sísmica homogénea y susceptibilidad a la licuefacciónInstituto Geológico y Minero de España, EspañaBureau de recherches géologiques et minières, FranciaServicio Geológico Nacional, República DominicanaDepartamento de Geología, Universidad de Atacama, Chil