The propagation and linkage of normal faults: insights from the Strathspey-Brent-Statfjord fault array, northern North Sea

Through examination of the scaling relations of faults and the use of seism ic stratigraphic techniques, we demonstrate how the temporal and spatial ev olution of the fault population in a half-graben basin can be accurately re constructed. The basin bounded by the >> 62-km-long Strathspey-Brent-Statfj ord fault array is located on the western flank of the Late Jurassic northe rn North Sea rift basin. Along-strike displacement variations, transverse f ault-displacement folds and palaeo-fault tips abandoned in the hangingwall all provide evidence that the fault system comprises a hierarchy of linked palaeo-segments. The displacement variations developed while the fault was in a prelinkage, multisegment stage of its growth have not been equilibrate d following fault linkage. Using the stratal architecture of synrift sedime nts, we date the main phase of segment linkage as latest Callovian - middle Oxfordian (10-14 Myr after rift initiation). A dense subpopulation of faul ts is mapped in the hangingwall to the Strathspey-Brent-Statfjord fault arr ay. The majority of these faults are short, of low displacement and became inactive within 3-4 Myr of the beginning of the extensional event. Subseque ntly, only the segments of the proto-Strathspey-Brent-Statfjord fault and a conjugate array of antithetic faults located 3.5 km basinward continued to grow to define a graben-like basin geometry. Faults of the antithetic arra y became inactive similar to 11.5 Myr into the rift event, concentrating st rain on the linked Strathspey-Brent-Statfjord fault; hence, the basin evolv ed into a half-graben. As the rift event progressed, strain was localized o n a smaller number of active structures with increased rates of displacemen t. The results of this study suggest that a simple model for the linkage of 2-3 fault segments may not be applicable to a complex multisegment array.