Abstract - Normal faults are often complex three-dimensional structures comprising multiple sub-parallel
segments sepa-rated by intact or breached relay zones. Relay zones are classified according to whether they step in
the strike or dip direction and whether the relay zone-bounding fault segments are unconnected in 3D or bifurcate
from a single surface. Complex fault surface geometry is described in terms of the relative numbers of different types
of relay zones to allow comparison of fault geometry between different faults and different geological settings. A
large database of fault surfaces compiled primarily from mapping 3D seismic reflection surveys and classified according
to this scheme, reveals the diversity of 3D fault geometry. Analysis demonstrates that mapped fault geometries depend on
geological controls, primarily the heterogeneity of the faulted sequence and the presence of a pre-existing structure, as
well as on resolution limits and biases in fault mapping from seismic data. Where a significant number of relay zones are
mapped on a single fault, a wide variety of relay zone geometries occurs, demonstrating that individual faults can
comprise segments that are both bifurcating and unconnected in three dimensions.
Earth-Science Reviews, 216, 103523, May 2021.