Using soil-compaction rates by the European Ground Motion Service (PS-InSAR) to estimate, at high spatial resolution, the site conditions of the Grenoble basin (French Alps) for its response to earthquakes

Abstract. In the basin of Grenoble (France), we explore the potential of the compaction rates of Quaternary sediments as measured by PS-InSAR, and freely delivered by the Copernicus service EGMS, to serve as a new proxy for mapping site-condition parameters used in seismic-hazard assessment (fundamental resonance period T₀ of the soil and sediment thickness H_bed ). The Grenoble basin is known for its strong site effect that largely amplifies seismic waves emitted by earthquakes. We develop a specific processing protocol of the EGMS data to account for its high inherent noise (involving adequate spatial smoothing, and quality filtering of the measurements considered), and propose a statistical referencing so the developed models are fully independent of the EGMS dataset chosen as input. The models are applicable in Grenoble in high spatial resolution and result in over 100 000 new estimation points of the site conditions in the entire basin area. This work highlights the huge potential of satellite imagery to complement site-characterisation and microzonation studies specifically in urbanized valleys.