Failles actives et trace des séismes en surface : l'approche paléosismologique

The identification of seismogenic faults in regions with low level seismicity is a major problem in earth sciences. Recent developments of tectonic studies in earthquake-prone areas point out critical questions such as (1) what is the probability of occurrence of a large earthquake (M>6.5) in intraplate Europe? and (2) how much the morphology may record and preserve successive coseismic movements in regions with fault slip rates lower than 1 mm·yr⁻¹? In palaeoseismology, the identification of coseismic movements and related active fault parameters results from integrated field investigations that include geomorphic analysis of fault scarps, geophysical prospecting and trench investigations. Methodologies developed in regions with high seismic strain rates (fault slip rates higher than 1 mm·yr⁻¹, interplate regions) are of primary importance for the fault identification in regions with low level of seismicity (intraplate domains). Examples of active faults illustrate their physical properties and contribute to a better understanding of the faulting behaviour and related seismic hazard.