Displacement loss on growth faults due to sediment compaction

Compaction models of normal growth faults, combined with displacement data from a natural growth fault (Cape Egmont Fault, New Zealand), are used to quantify the loss of displacement arising from compaction, in circumstances where growth faults are blanketed and buried by compacting sediment in both footwall and hangingwall. Comparison of imposed tectonic displacements with the preserved displacements indicates that although the thicknesses of sand/shale sequences may decrease by up to c. 55% due to compaction, associated losses in displacement on growth faults are typically <20% because they displace partially compacted sediments. The importance of displacement loss generally increases with increases in the depth range over which fault displacements migrate along the compaction curves and in the percentage shale of the faulted sequence. Displacement loss due to compaction is relatively small (<c. 15%) for sand or mixed sand-shale sequences with growth indices greater than c. 0.1 (equivalent to the ratio of the fault throw rate and footwall sedimentation rate), and in these strata decompaction is not required to decipher first-order displacements and fault-growth histories. Decompaction of displacements is of most benefit in circumstances where growth sequences have a high shale content (>70%) and post-faulting burial is large (i.e. km-scale).