Fault reactivation and fluid flow along a previously dormant normal fault in the northern North Sea

Detailed seismic imaging and in situ stress and pore-pressure measurements are used to analyze reverse-fault reactivation of a long-dormant normal fault in the northern North Sea. Fault reactivation is caused by three factors: (1) a recent increase in the compressional stress in the area associated with postglacial rebound, (2) locally elevated pore pressure due to the presence of natural gas in a hydrocarbon reservoir on the footwall side of the fault, and (3) a fault orientation that is nearly optimally oriented for frictional slip in the present-day stress field. We demonstrate that the combination of these three factors induces fault slippage and gas leakage along sections of the previously sealing reservoir-bounding fault. We argue that similar pore-pressure triggering of fault slip in the crust may occur because of the accumulation of gas columns of, e.g., CO₂ and He in the vicinity of tectonic faults.