NUMERICAL-MODELS OF FAULTING AT OBLIQUE SPREADING CENTERS

Obliquely spreading mid-ocean ridges, such as the Reykjanes Ridge, dis play two distinct fault sets distinguishable by orientation and positi on: on-axis faults are oriented oblique to both the trend of the axis and the normal to the relative plate separation vector, while faults o n the flanks strike approximately parallel to the ridge axis. Numerica l modeling techniques are used here to simulate the development of fau lting on the Reykjanes Ridge. Stresses acting in a cross section throu gh the lithosphere at a slow spreading ridge are investigated using th e fast Lagrangian analysis of continua (FLAC) explicit difference mode ling software. The predicted stresses from the cross-sectional models are imposed as a condition in boundary element models of fracture prop agation and linkage. On-axis fault simulations run under conditions si milar to the Reykjanes Ridge successfully reproduce the mapped distrib ution of faults and predict the observed orientation of the axial volc anic ridges. Simulations of fractures away from the axis show the deve lopment of axis-parallel faults by the interaction and linkage of frac tures which have been rafted off-axis, also in accord with observation s. Stresses modeled in cross section favor downdip displacement on fau lts dipping toward the ridge axis.