Fault patterns in the cretaceous and tertiary (end syn-rift, thermal subsidence) succession of the Porcupine Basin, offshore Ireland

Fault lengths, distributions and orientations were determined at six post-Jurassic horizons in the Porcupine Basin, offshore Ireland. Three rifting periods occurred in the Porcupine Basin with fault orientations and lengths measured for the second and third of these. Dominant fault directions changed through time, while remaining broadly parallel to the basin margins, particularly in the southern part of the basin and especially for the larger faults. Observed changes in activity suggest that strain was evenly distributed throughout the basin during the periods of extension. Length population curves for the faults throughout the basin show an approximate straight line log-log relationship between cumulative number and fault length, indicating that the fracture length populations are self-similar over a range of scales. The fault patterns reflect the response to the transition from a syn-rift dominant phase of basin evolution to one where the development was primarily influenced by thermal subsidence with subsidiary rifting.