STRAIN AND SCALING OF FAULTS IN THE CHALK AT FLAMBOROUGH-HEAD, UK

Analysis has been made of the orientations, displacements and spacings of 1340 extensional faults, with displacements of up to 6 m, along an almost completely exposed 6 km length of cliff. This data set has been used to study how fault populations account for strain in a region and to study relationships between different scales of fault. Strains have been estimated; the maximum and intermediate extensions are sub-horizontal, with approximately equal extension (e almost-equal-to 0.01) in all horizontal directions. It can be inferred that the minimum extension (maximum compression) was sub-vertical, but that the wide variety of fault orientations and cross-cutting relationships resulted from variable horizontal extensions. Some faults have oblique-slip slickenside lineations, which imply a period of later, dominantly NNW-SSE extension, which possibly developed as the exposure-scale faults finked up E-W-striking larger-scale normal faults, effectively forming a single wide fault zone. Graphs of displacement per unit distance are used to illustrate variations in displacement. The scaling of fault displacement appears to follow a power-law relationship. The differences in orientation between the small-scale and large-scale faults precludes a simple estimation of the total strain over all scales.