Influence of the Convergence and Stepover Angles in the Structural Style of Strike-Slip Systems: Analogue Models

The presented results of analogue models analyze the influence of the relation between the convergence angle and the stepover angle on strike-slip systems. The experiments include 2 stepovers arrays to generate both transpressional and transtensional zones. These experiments were prepared using 5 cm thick sandpack (sand diameter <500 μm, internal friction angle 30°, density 1,400 kg/m3) to simulate brittle deformation; the base of the model was formed by thin zinc base plates, one of them mobile, cut in such a way so as to produce restraining and releasing strike-slip stepovers; the rate convergence was constant. We carried out 3 series of experiments in which the convergence angles (0°-60°) and stepover angles (30°-60°) were varied systematically. Preliminary results indicate that by increasing the angle between the stepover and the convergence vector: a) the restraining area generated a positive flower structure that is progressively wider; b) progressively more reverse faults which absorb more shortening were generated. Locally, strike-slip faults in the positive flowers were accommodated by the geometry of the stepover base. Areas most complex involved the development of normal faults, which subsequently were inverted. In conclusion, the relation between the convergence and stepover angles is a main factor that determines the structural style of flowers structures on strike-slip systems. This work was done through the ACT-18 PBCT project.