[en] In this set of articles on the way earthquakes and seismic risks are addressed and studied by the IRSN, particularly in the post-Fukushima context (some consequences of this accident are evoked), a first one gives a brief overview of the French situation related to earthquakes which is assessed every ten years, outlines that some dykes, notably those close to the Tricastin nuclear plant, must be strengthened to resist to an extreme earthquake. The case of the La Hague plant is then addressed where other new nuclear installations than reactors are also to be strengthened through the use of reinforcements. As example of field actions, the study and control of sedimentary areas is briefly evoked