NUMERICAL MODELING OF PROPAGATION AND OVERLAP OF THRUST FAULTS, WITH APPLICATION TO THE THRUST-FOLD BELT OF CENTRAL ALBERTA

We use two computer programs to analyze the propagation of multiple th rust faults and their influence on the geometry of a thrust belt. They use algorithms based on current equations of fault propagation to gen erate graphical simulations. The simulations are used to demonstrate a model of thrust propagation and thrust belt development that fits cur rent knowledge of fault propagation. An alternative to the thrust tran sfer zone model is proposed, called thrust overlap zones. The computer simulations provide useful information about the generation and behav ior of multiple faults. The number of faults, the positions of their n ucleation points and hence their density, the rock properties; and rat e of fault propagation govern the uniformity of the shortening along t he thrust belt. Thus, shortening of a thrust belt can be distributed m ore evenly by means of propagation of a large number of small faults t han by a few large faults. The final geometry of a large thrust fault on a geological map provides few clues about its origin, i.e. whether it was produced by the coalescence of a series of en echelon thrust fa ults or from only a single fault. A simple kinematic model based on ma p length and position of known thrust faults imitates the curved fault map patterns of a segment of the thrust-fold belt of central Alberta.