Numerical modeling of Cenozoic stress patterns in the mid‐Norwegian margin and the northern North Sea

Abstract

Numerical modeling of Cenozoic stress patterns in the northern North Sea and the mid‐Norwegian margin is presented, and the sense of potential slip along major fault planes belonging to the two areas is restored. We assume that the main regional source of stresses is the Atlantic ridge push as demonstrated by previous studies. Furthermore, we also assume a nearly consistent NW‐SE strike for the far‐field stress from continental breakup between Greenland and Norway (earliest Eocene) to present day. First, we applied the commercial two‐dimensional distinct element method (UDEC) to simulate Cenozoic stress and displacement patterns in the study area. Variations in rheology and major fault zones were introduced into the model. The Møre‐Trøndelag Fault Complex and its inferred continuation into the Shetland Platform forms the major mechanical discontinuity in the model. Second, we used the SORTAN method, developed at the University of Paris VI, to predict the sense of potential slip along major fault planes. The input for the SORTAN model was constrained by the geometry of the selected fault planes and local principal stress directions extracted from the UDEC modeling. Our results show that the Møre‐Trøndelag Fault Complex and its inferred continuation into the Shetland Platform act as a weak fault zone. This fault zone divides the study area into two different stress provinces: the continental margin and the northern North Sea. This result agrees well with the observed differences in Cenozoic structural evolution of the two areas. Compressive structures are observed along the continental margin, whereas relative tectonic quiescence characterizes the northern North Sea during the Tertiary. The restored stress patterns in the northern North Sea and the mid‐Norwegian margin also agree well with the observed present‐day stress configuration. Our analysis demonstrates a method to reconstruct the sense of slip on major fault planes by combining two complementary numerical tools (UDEC and SORTAN). As a result, it is demonstrated that oblique‐slip motions are mainly expected, in particular, strike‐slip and reverse dip‐slip faulting are simulated.