Reassessment of the structural framework of western Provence (France): consequence on the regional seismotectonic model
Résumé
Reprocessing and interpretation of the petroleum seismic profile 81SE5b, located between the Luberon Massif and the Arc Basin, have provided new data on the Pyrenean and Alpine thrusting in western Provence. Among the principal results, it is shown that a) the repetition of the Mesozoic succession observed in the Eguilles1 borehole is due to a north-dipping south-verging thrust, and b) the Trévaresse and Aix-Eguilles thrusts are deep structures rooted in the Triassic at a depth of between 7 and 8 km. The implication of this new knowledge on the seismotectonic model of western Provence is that the front of the Alpine deformation between the Aix-en-Provence and Salon-Cavaillon fault systems, which acted as lateral ramps, lies some 7 km farther south near the northern limb of the Arc syncline. In addition, it is seen that the Alpine-Provence thrusts, considered as still active (having given rise to the 1909 earthquake with an epicentral intensity of VIII-IX), are not shallow reverse faults but correspond to major tectonic structures affecting the full thickness of the Meso-Cenozoic cover.