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Variations in Slip as from Indicator of Fault-Related Folding Style

Hughes, Amanda N.1; Shaw, John H.1
1 Earth and Planetary Sciences, Harvard University, Cambridge, MA.

Over the past two decades, many fault-related fold models have been successfully applied to describe structures that are common in fold-and-thrust belts. Due to the proliferation of models, it is often difficult to determine which model can most effectively be applied to a given structure. Additionally, there are many structures that are sufficiently complex, or have exhibited different fault-related folding styles over their history, that they are not well characterized by a single model. Thus, it is desirable to have an independent means of discerning the style of fault-related folding present in a structure, which is critical for characterizing the geometry and predicted strain patterns in petroleum reservoirs. We find that measuring the amount of slip with distance along the fault from the fault tip, or the "slip profile," can provide insights into structural style. Each of the major types of compressional fault related fold models—fault-bend, shear fault-bend, and fault-propagation—have distinctive slip profile patterns. We show a series of structures imaged with seismic reflection from a variety of regions illustrating that the predicted slip profiles for each of these fault-related-fold models are consistent with observations of natural structures, which we then compare to results from discrete element mechanical models. By establishing that the slip profile characteristic of each folding model is unique and applicable to natural examples, we are then able to employ the slip profile for a complex, multi-stage natural structure to recover its deformation history in a manner consistent with the different fault-related-folding mechanisms. Analysis of the growth strata geometry further supports these interpretations, suggesting that analyzing slip profiles serves as an effective means of determining structural style and deformation history.


AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009