Topological Characterization of a Fault Network Along the Northern North Sea Rift Margin

Abstract

The factors that control the spatial variation of the topological characteristics of normal fault networks at the rift-scale are poorly understood. Here, we use 3D seismic reflection data from the northern North Sea to investigate the spatial variation of the geometry, topology, and strain heterogeneity of the Late Jurassic normal fault network along the rift margin. Our results show that fault orientation varies spatially along the rift margin. Normal faults within fault blocks that are adjacent to the North Viking Graben exhibits dominant N-S and NE-SW strikes that are sub-parallel to the graben axis and associated step-over, whereas in fault blocks farther from the graben, there is a dominant NW-SE strike. Furthermore, we identify two broad topological domains within the fault network: (a) dominated by isolated nodes, partially connected branches, and low fault connectivity, and (b) dominated by abutting nodes, fully connected branches, and moderate to high fault connectivity. These topological domains correlate with previous sub-division of the rift margin in the northern North Sea into platform and sub-platform structural domains, respectively. There is also a positive correlation between the spatial variability of the fault orientations and intensity, with the fault network connectivity, highlighting the relationship between normal fault geometry and topology. We conclude that the across and along-strike variation in strain, presence of pre-existing structures, and accommodation zone-related deformation are key factors influencing the spatial variation of fault network properties at the rift scale.