The three-dimensional geometry of relay zones within segmented normal faults

Normal faults often comprise arrays of fault segments. The boundaries between adjacent fault segments, relay zones and relay ramps can be of crucial importance to fluid migration pathways across and along faults and for across-fault reservoir juxtaposition. However, despite the increased number of studies of faults in high quality 3D seismic data, the three dimensional geometric or kinematic properties of relay zones or the controls on their 3D geometry are still unclear. This contribution investigates the characteristics of three dimensional segmentation based on an extensive collection of normal faults and relay zones in different geological settings. Our analysis shows that relay zones most often develop by bifurcation from a single fault surface but can also arise from the formation of segments which are disconnected in 3D from their inception. Relay zones generally occur between fault segments that step in the dip or strike direction, and intermediate oblique relay zones are less frequent. When combined together, these different geometries can form a complex spectrum of fault segmentation, whose characteristics can be related to underlying geological controls, such as the mechanical heterogeneity of the faulted sequence and the influence of the basement structure