Numerical modeling of propagation and overlap of thrust faults, with application to the thrust-fold belt of central Alberta

Abstract

We use two computer programs to analyze the propagation of multiple thrust faults and their influence on the geometry of a thrust belt. They use algorithms based on current equations of fault propagation to generate graphical simulations. The simulations are used to demonstrate a model of thrust propagation and thrust belt development that fits current knowledge of fault propagation. An alternative to the thrust transfer zone model is proposed, called thrust overlap zones. The computer simulations provide useful information about the generation and behavior of multiple faults. The number of faults, the positions of their nucleation points and hence their density, the rock properties; and rate of fault propagation govern the uniformity of the shortening along the thrust belt. Thus, shortening of a thrust belt can be distributed more evenly by means of propagation of a large number of small faults than 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 échelon thrust faults or from only a single fault. A simple kinematic model based on map length and position of known thrust faults imitates the curved fault map patterns of a segment of the thrust-fold belt of central Alberta.