Scaling laws between fault displacement, lithology and damage zone widths in carbonates

ABSTRACT: The geometrical characterization of fault damage zones is a very difficult task, in particular for deep subsurface faults. Many efforts have been focused on the assessment of the damage zone width. Seismic methods have demonstrated that when high resolution data are available, those methods can identify the fault architecture. Unfortunately, most conventional seismic data rarely allow such identification. Alternatively, several studies based on outcrop observations have proposed power laws between the fault displacement (or fault throw) and the damage zone width. However, a significant dispersion observed in data makes the practical application of such relationships debatable. Parameters such as lithology and mechanical properties of the host rock can be responsible for the scattering. Nonetheless, the impact of geomechanical parameters on the definition of damage zones has not been explored. Considering the results of several geomechanical models and field data, an artificial neural network (ANN) has been developed in order to provide damage zone widths including not only the impact of the fault displacement, but also geomechanical parameters. That ANN is used in this study to obtain scaling laws capable of providing damage zone widths of faults in carbonates. The results show that both the coefficient and exponent of power laws are influenced by geomechanical properties of the host rock including elastic and strength parameters. From the comparison with field data, we show that the new relationships can partially explain the observed dispersion between the fault displacement and the damage zone width.