Numerical modeling of Cenozoic stress patterns in the mid-Norwegian marginand the northern North Sea

Numerical modeling of Cenozoic stress patterns in the northern North Sea an d the mid-Norwegian margin is presented, and the sense of potential slip al ong major fault planes belonging to the two areas is restored. We assume th at the main regional source of stresses is the Atlantic ridge push as demon strated by previous studies. Furthermore, we also assume a nearly consisten t NW-SE strike for the far-field stress from continental breakup between Gr eenland and Norway (earliest Eocene) to present day. First, we applied the commercial two-dimensional distinct element method (UDEC) to simulate Cenoz oic stress and displacement patterns in the study area. Variations in rheol ogy and major fault zones were introduced into the model. The More-Trondela g Fault Complex and its inferred continuation into the Shetland Platform fo rms the major mechanical discontinuity in the model. Second, we used the SO RTAN 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 prin cipal stress directions extracted from the UDEC modeling. Our results show that the More-Trondelag Fault Complex and its inferred continuation into th e Shetland Platform act as a weak fault zone. This fault zone divides the s tudy area into two different stress provinces: the continental margin and t he northern North Sea. This result agrees well with the observed difference s in Cenozoic structural evolution of the two areas. Compressive structures are observed along the continental margin, whereas relative tectonic quies cence characterizes the northern North Sea during the Tertiary. The restore d stress patterns in the northern North Sea and the mid-Norwegian margin al so agree well with the observed present-day stress configuration. Our analy sis demonstrates a method to reconstruct the sense of slip on major fault p lanes 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 arc simulated.