Multiscale fracture analysis along the French chalk coastline for investigating erosion by cliff collapse

Abstract

Abstract Coastal cliffs of Upper Normandy and Picardy are eroded by cliff collapses of various sizes. This paper presents a multi-scale analysis of the pre-existing fractures embedded within the Cretaceous chalk. About 20 representative sites equally spaced along the 120km long coastal section were analysed and compared to a continuous structural analysis of the coast derived from aerial photographs taken in 1986. Ancient collapses interpreted on the aerial photos were compared to the pre-existing fracture content. Regional faults, pre-1986 collapse location and fracture density are spatially correlated. However, recent collapses observed on the field between 1998 and 2001 did not systematically correlate to the pre-existing fracture occurrence and therefore, there is no clear link between recent collapse and the regional faults.