Deformation around stepovers in strike-slip fault zones

This stuck addresses the kinematics of stepovers in strike-slip fault zones, where left-lateral faults step rightward or right-lateral faults step leftward. A stepover is regarded as containing an internal strike-slip fault, whose ends link to transform faults, surrounded by uniformly distributed deformation. The kinematics are governed by k. the ratio of slip rates on the internal fault and transform faults, and gq, the angle between these taults. The convergence direction across the deformation, at angle Ψ to the internal fault, is an azimuth along which vectors do not rotate around vertical axes. The Lebanon stopover on the Dead Sea fault zone and the Big Bend stepover on the San Andreas fault zone provide case studies. In Lebanon, the time-averaged deformation since 15 Ma involves k 0.06.32 ° and ψ ~ 34 °. It accounts for 30 ° of anticlockwise rotation of Cretaceous magnetization vectors in the Lebanon mountains, and 50 rotation of Jurassic vectors. The present phase of deformation around the Big Bend, which began at 5–7 Ma and imolves k 0.89. θ ~ 20 ° and Ψ ~ 98 °, has instead only caused small rotations (both clockwise and anticlockwise). Much of this regionʹs structure, including the dramatic (up to ~ 80 °) clockwise rotation of magnetization vectors in the Transverse ranges, is shown to relate instead to an earlier deformation phase with much lower k