DARE: Dense ARray for seismic site effect Estimation

• Applicants: Professor Dr. Fabrice Cotton; Dr. Matthias Ohrnberger
• Subject Area: Geophysics ; Palaeontology
• Term: from 2019 to 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 431362334

Seismic hazard represents a major worldwide scientific issue in view of potential catastrophic consequences experienced by people and facilities. Methodological developments to improve our ability to evaluate the seismic hazard are then of particular importance. We focus here on the so-called site effects that correspond to the modification of the seismic motion by the local geological configuration and that can lead to dramatic seismic amplifications. By being related to local conditions, site effects are highly variable from one site to another. That is why site-specific studies can greatly contribute to improve the hazard prediction at a specific site in comparison to ergodic estimates based on data from global databases. However site-specific studies have historically been considered difficult to carry out in low-to-moderate areas (such as France and Germany) where moderate to large earthquakes have long return periods. The DARE project proposes to exploit data from 2 complimentary dense passive experiments (100s of captors) that will be acquired on one specific km-scale sedimentary basin in the French Rhône valley. These data will be used to investigate the contribution and interest of innovative methods combining dense array processing and the use of seismic noise to offer possibilities to perform site-specific studies using relatively short temporary experiments in low-to-moderate areas. The density of instruments proposed will help to 1) improve the spatial resolution of imaging studies, allowing for a better characterization of the basin and 2) to catch the variability and multi-dimensional features of the site effects. We propose to adopt a multi-approach estimation of site effects using different seismic observations (noise & seismicity) and approaches (numerical & empirical). This strategy will allow us to propose and confront alternative methods; evaluate their own interests, uncertainties and limitations. The application of this integrated procedure in the Rhône Valley will lead to a robust estimation of site effects in an area where many critical infrastructures are located. Beyond improving our knowledge of this specific basin, the results of the project DARE will more generally contribute to improve seismic site effect estimation in terms of 1) methodological developments, 2) understanding of physical processes leading to seismic amplifications and 3) observations on km-scale western European sedimentary basins. Site-specific results obtained in this project will be confronted to estimates based on ergodic approaches that are commonly used in seismic hazard assessment studies especially in low-to-moderate areas. This will help understand the conditions of applications and limitations of the use of such ergodic approaches in seismic site effect estimations.

• DFG Programme: Research Grants
• International Connection: France
• Cooperation Partners: Dr. Pierre Boue; Dr. Berenice Froment
• Co-Investigators: Dr. Annabel Händel; Dr. Marco Pilz