Spatial distribution of damage and strain within a normal fault relay at Kilve, U.K.

Abstract

Using outstanding outcrops on the Somerset coast (UK) we investigate a mesoscale fault relay and its associated linkage damage zone, quantifying spatial distributions in deformation and strain at different scales. The relay is bound by two large normal faults, which down-throw ∼80 m to the south and overlap by ∼170 m creating a relay ramp. Stratigraphic separations measured along each bounding fault decrease rapidly within the relay ramp, where enhanced development of smaller N-down-throwing faults contributes ∼50% of the total cumulative separation. Spatial distributions of deformation indicate much heterogeneity outside the relay ramp, with deformation localised to a few large faults, and more homogenous deformation inside the relay ramp due to numerous smaller damage faults. Veining throughout the relay is localised around fault planes but does not correlate with fault displacement. Instead, high vein intensities (>10 m−1) and strains (>25% extension) form wide zones at fault tips and intersections, correlating with high local stress. Strain partitioning between the various structures (relay bounding faults, small damage faults, veins) varies along the relay. Decreases in contributions from the bounding faults are balanced by increases from damage faults, highlighting a changing strain distribution that maintains strain compatibility throughout the relay.