Abstract - Contractional relay zones between pairs of normal faults are sometimes associated with multiple antithetic faults in a geometry similar to that found in Riedel shear
zones. Detailed fault displacement profiles of outcrop examples of this geometry demonstrate that the antithetic faults accommodate the transfer of displacement
between the synthetic faults that bound the relay zones. The throw on individual antithetic faults, or R′ shears, is typically constant across relay zones while the throw
profile on the synthetic faults, or R shears, is stepped; the steps occurring across branchpoints with abutting R’ shears. Transfer of fault displacement occurs by a
combination of block rotation and irrotational block translation within the relay zone. As fault throw increases, contractional relay zones are by-passed by the linkage
of the synthetic faults, in a manner analogous to the formation of P-shears by the linkage of R shears in classic Riedel shear experiments, but with the original relay
zone structure still preserved within the fault zone. With yet further strain bedding may rotate into near-parallelism with the fault surface, with the original
geometrical configuration of the relay zone difficult to unravel.
Journal of Structural Geology , 168, 104827, doi: 10.1016/j.jsg.2023.104827, 2023.