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DARE Dense ARray for seismic site effect Estimation

Time Frame: 2020-2023

Funding: Deutsche Forschungsgemeinschaft & Agence Nationale de la Recherche

Principal Investigator:Fabrice Cotton

Personnel:Marco Pilz, Chuanbin Zhu, Annabel Händel

Cooperations: Universität Potsdam, IRSN Paris, Universität Grenoble, Frankreich

Site effects are key players in seismic hazard assessment. The level of seismic hazard in critical zones, such as sedimentary basins, can increase notably subjected to the specific characteristics of the basin. These include geologic structure, nature and composition of the subsurface. The properties of the shallow subsurface in basins can result in an amplification of the seismic motion. In these sedimentary basins, seismic waves can be trapped and the geometry of the soft deposits can further affect the ground motion by increasing both the duration and amplitude of the shaking. Site assesment is important in populated areas such as big cities (e.g. Mexico City, Mexico; Los Angeles, USA; Tokyo, Japan; Grenoble, France) or industrialized areas with critical infrastructures (the case of the project). The project DARE proposes an integrated study of seismic site effects on the deep and elongated Messinian Rhone Canyon (French Rhone Valley). We will focus in the area of the widespread Tricastin Nuclear Site (TNS) that consists of a power plant and a collection of nuclear fuel cycle facilities located above the canyon. This canyon was dug during the Messinian Salinity Crisis (MSC) in the Mesozoic substratum (Cretaceous limestones and sandstones). This canyon is filled with Pliocene marine sediments (sands and clays) nowadays covered by the Rhone Quaternary terrace (Holocene). Lithological information from boreholes reaching the bedrock and preliminary geophysical campaigns indicate that the canyon can reach locally >500 m and may be deeply incised. The strong material contrast between the sedimentary filling and the substratum, as well as its expected confined geometry make this canyon a good candidate for generating site effects.

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