ANALYSIS OF THE REACTIVATION OF NORMAL FAULTS IN A CONTEXT OF INVERSION KINEMATCS: PHYSICAL MODELING OF CONTRIBUTION WITH USE OF PIV( PARTICLE IMAGE VELOCIMETRY)
Physical modeling; Normal fault; Positive inversion.
Analog modeling has been used since the XIX century to simulate geological structures in order to understand the mechanisms that control its geometry and kinematics. The use of this tool in the oil industry, to help seismic interpretations (mainly to search for structural traps), helped to spread the use of this tool in the literature. Studies involving basins inversion are developed to improve understanding factors that influence the reactivation of pre-existing structures as well as their geometry. In this work, we analyze the construction of the structural architecture of a fault system that underwent positive inversion, and analyzed the relationship between the generation of new faults and reactivation of pre-existing normal faults during a contraction event. In addition, the behavior and distribution of strain along the deformation process ware performed based on images obtained and processed by Particle Image Velocimetry (PIV) system. Two series of experiments were developed: i) Series I: We analyzed the generation of fault sets associated with a main lístrica fault and their reactivation during a kinematics inversion event. Two types of models were performed: one with lístrica fault, orthogonal to the direction of tension and compression (IA series), while in the other the lístrica fault was oblique ("α" = 80) (IB series). The final structural configuration after inversion showed major fault and some of the normal faults (delimiting the grabenforme structure) reactiveted. Thrust and backthrust were developed from the basal portion of listric fault, or in the upper part of the model, propagating towards the base of grabenform structure; ii) Series II: We analyzed the generation of faults associated with the formation of a planar master fault, orthogonal to the direction of both tension and compression. In these experiments, the role of rheology during normal faults reactivation was analyzed. Three types of experiments were done varying the materials of the pre-tectonic sequences: only sand (IIA series); sand and gesso (IIB series); and sand and clay (IIC series). These experiments displayed the final architecture with normal faults completely or partially reactivated, and the developed thrusts and backthrust sliced up the basal portion of the grabenforme structure. The PIV data showed that during the first stages of compression, deformation was absorbed mainly by rearrangement of the granular material (compactation) and only after this process fault reactivation (or new fault) occurs. During deformation, some faults alternated intervals of activity and inactivity.