Modes of reverse reactivation of domino-type normal faults: experimental and theoretical approach

Experiments with sand-cement models show that reverse reactivation of a set of parallel faults bounding domino blocks takes place in two principal modes. In (Mode I) reactivation, the domino blocks undergo counter-rotation during contraction while normal faults are reactivated as reverse faults. Mode II reactivation occurs by fault-block translation. We present a theoretical analysis of the two modes which considers forces and their rotational moments in a domino block and show that low-angle normal faults are commonly reactivated in Mode II. By contrast, steep faults are reactivated in Mode I. Furthermore, fault reactivation depends on the initial fault spacing. A large initial fault spacing opposes fault reactivation, especially in Mode I. Instead, the system deforms along new thrusts, dipping opposite to the normal faults. We generate reactivation parameters for the conditions of the two modes as functions of the ratio (R) between fault spacing and effective thickness of fault horizon, the fault dip (θ), the coefficient of friction (μ) and the ratio of principal stresses (Sr) during late contraction.