DISCRETE-ELEMENT MODELS OF ACTIVE SALT DOME

A two-dimensional, discrete-element modeling technique is used to investigate the evolution of active dome structures. In the model, we represent the cover as a series of soft spheres that obey Newton's equations of motion and interact with elastic forces under the influence of gravity. Faulting/fracturing is represented by a transition from repulsive-attractive forces between elements to solely repulsive forces. The model is used to investigate the initiation and growth of the fault system in the homogenous overburden strata of active domes, including their propagating features and the deformation mechanism. The inside movement features are demonstrated by the velocity maps. Models reproduce some typical structures of 2-D active salt domes. Both listric and anti-listric normal faults are observed. Results from the discrete-element modeling show the significant controls of overburden strata strength on the geometry and evolution of the fault system. The brittle cover tends to produces roughly symmetric faults, while the ductile cover is more likely to develop asymmetric faults. In addition, more faults are observed in the brittle cover than the ductile cover. The neutral cover has symmetric fault pattern in the early stage and the final stage of its evolution, with asymmetric deformation in the middle stage. All faults developed in the brittle and neutral cover models are normal faults. However, in the highly ductile cover model, we observe one inverted reverse fault near the shoulder of the dome. Modeling results are compared to physical experiments and natural examples.