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Analogue-Modelling and Section-Balancing |
Laboratoire de Tectonique, Universite de Rennes, 35042 Rennes, France
Scaled physical models of extensional structures associated with fault reactivation were achieved in sand by superimposing extensional tectonics on thrust faults created during prior episodes of horizontal shortening. The extension produced three distinct responses: selective reactivation of pre-existing thrusts, favouring the steepest thrusts and those dipping more than a critical value; development of new normal faults that were linked to or developed within the zone of thrust faults; or generation of new normal faults in previously unfaulted domains. Linked normal faults showed a wide range of orientations and most dipped less steeply than the unlinked faults, which had dips clustered about the value predicted from the internal friction coefficient of sand. During extension of a distributed fault model, reactivation of existing thrusts influenced the location, dip direction, and dip magnitude of linked normal fualts. Compared to natural fault systems, the models showed many geometric similarities especially regarding linked normal faults.
