Was the Trévaresse thrust the source of the 1909 Lambesc (Provence, France) earthquake? Historical and geomorphic evidence

Abstract

The destructive ‘Lambesc’ earthquake that struck southeastern France on 11 June 1909 reached maximum MSK intensity of IX. Critical reassessment of macroseismic observations shows that the VIII and VII isoseismal contours surround the Trévaresse ridge, a 15 km long, post-Miocene anticline. A rather steep escarpment, several tens of meters high, marks the southern flank of this fold. A locally steeper cumulative scarp, with, at one place, a south-facing free-faced scarplet, probably marks the emergence of successive surface ruptures, perhaps the last one in 1909. The bulk of the evidence suggests that the 1909 Lambesc earthquake activated a north-dipping thrust ramp below the growing Trévaresse anticline.