Do fault-related folds follow the same scale law properties as their associated faults?

Abstract

The scaling law distribution properties of fault-related folds were assessed in comparison to the distributions of their associated faults to determine whether or not they are governed by the same scaling law properties. The fault-related fold and fault data were collected from three- dimensional seismic data modelled in TrapTester and Petrel from the Gulf of Mexico (TrapTester), Gulf of Gabès (TrapTester) and the Inner Moray Firth (Petrel). They were sampled by one- dimensional multiline sampling (TrapTester) and two-dimensional (Petrel) fault and fold length sampling. To ensure the accuracy of this data collection method a comparative test of methodologies was carried out using the Gullfaks, North Sea data set and comparing it to the results published by Fossen and Rørnes (1995). By validating the methodologies (TrapTester) used the data sets were analysed using the Kolmogorov-Smirnov and Anderson-Darling test on a “moving window” in R to assess the scaling law distributions of the data. Based on previous findings from published work the power law distribution was tested first since fault populations are understood to follow this distribution. An exponential distribution and log-normal distribution were also tested. The results of this suggest that fault-related folds are not necessarily governed by the same distributions of the underlying fault population. It is proposed that fault-related folding is heavily controlled by the competence and thickness of the surrounding stratigraphic units, as well as the dip angle of the underlying faults. Incompetent beds will accommodate more folding compared to competent beds which are more likely to fault. A thinner stratigraphic unit will be unable to accommodate as much folding as a thicker stratigraphic unit. An underlying fault with a low dip angle will cause the overlying stratigraphic units to preferentially fault and won’t propagate as large a fold throw in comparison to underlying faults with a high dip angle.