Operations and main results of the ECORS project in France

Summary. The ECORS project was launched in 1983 with the aim of studying fundamental mechanisms of geodynamics in France. The ECORS deep seismic profiles have concentrated on a few structures of major significance: outer zone of the Variscan orogen in northern France, the basin formed during the Bay of Biscay's opening and transects of recent orogenic ranges (Pyrenees and Alps). The seismic profiles have been carried out with all the available modern techniques of industry and completed wherever possible by additional geophysical surveys (magnetism, gravity, MT, wide-angle and refraction seismics) and geological surveys. The first results already shed new light on major geodynamic phenomena such as variations in the frontal Variscan detachment, lower crust formation, crustal behaviour during orogenesis and variations in the formation of cratonic basins.