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Propagation of site effects: recording of ground movements in the pilot site effects areas of Grenoble and Nice

ca 2008

Description : This figure shows the ground movement records for the pilot site effect areas of Grenoble and Nice, showing great variability due to sediment fillings. Initial data from some Rap pilot sites have confirmed the existence of site effects in some Alpine valleys which, using the empirical Green functions method, can lead to higher ground movements than those recommended in national rules. The data also provided misunderstood observations at the moment, certainly related to the 3D geometry of certain environments, or to the complexity of the wave field in 3D stratified environments (basin edges, focusing of surface waves). Several teams are developing numerical simulation methods to quantify these responses during strong earthquakes. These are propagation methods in complex two- or even three-dimensional environments and methods that estimate the non-linear behaviour of soils under high stress. The evaluation of this non-linear behaviour is fundamental to assess whether the variability observed for small movements is transposable to large movements. The development of these calculation methods is associated with the development of methods for the geotechnical characterization of the subsoil in an economical and environmentally friendly way, using conventional methods (geophysics, geotechnics, or use of background noise, background noise correlations). This work is in line with the scientific objectives of the Permanent Accelerometer Network (Rap), which aims to understand site effects and seismic motion. The Rap is a specific action of the French Seismological and Geodetic Network Résif, a national research infrastructure dedicated to the observation and understanding of the structure and dynamics of the Inner Earth. Résif is based on high-tech observation networks, composed of seismological, geodetic and gravimetric instruments deployed in a dense manner throughout France. The data collected make it possible to study with high spatial and temporal resolution the deformation of the ground, surface and deep structures, seismicity on a local and global scale and natural hazards, and more particularly seismic events, on French territory. Résif is integrated into European (EPOS - European Plate Observing System) and global systems of instruments for imaging the Earth's interior as a whole and studying many natural phenomena.
Contributor : Véronique Bertrand <>
Submitted on : Tuesday, October 15, 2019 - 7:45:36 AM
Last modification on : Tuesday, July 27, 2021 - 9:36:02 AM
Long-term archiving on: : Thursday, January 16, 2020 - 1:18:46 PM