Numerical models of faulting at oblique spreading centers

Abstract

Obliquely spreading mid‐ocean ridges, such as the Reykjanes Ridge, display two distinct fault sets distinguishable by orientation and position: on‐axis faults are oriented oblique to both the trend of the axis and the normal to the relative plate separation vector, while faults on the flanks strike approximately parallel to the ridge axis. Numerical modeling techniques are used here to simulate the development of faulting on the Reykjanes Ridge. Stresses acting in a cross section through the lithosphere at a slow spreading ridge are investigated using the fast Lagrangian analysis of continua (FLAC) explicit difference modeling software. The predicted stresses from the cross‐sectional models are imposed as a condition in boundary element models of fracture propagation and linkage. On‐axis fault simulations run under conditions similar to the Reykjanes Ridge successfully reproduce the mapped distribution of faults and predict the observed orientation of the axial volcanic ridges. Simulations of fractures away from the axis show the development of axis‐parallel faults by the interaction and linkage of fractures which have been rafted off‐axis, also in accord with observations. Stresses modeled in cross section favor downdip displacement on faults dipping toward the ridge axis.