INFLUENCE OF MECHANICAL STRATIGRAPHY AND KINEMATICS ON FAULT SCALING RELATIONS

In order to document effects of mechanical anisotropy, fault geometry, and structural style on displacement-length (D-L) scaling relations, we investigated fault dimensions in the lithologically heterogeneous M onterey Formation exposed along Arroyo Burro Beach, California. The fa ults, which range in length from several centimeters to several meters , group into two populations: small faults confined to individual muds tone beds, and larger faults that displace multiple beds and often mer ge into bedding plane detachments. Whereas a linear correlation exists between displacement and length for small faults, displacement across large faults is independent of length. We attribute this deviation fr om scale-invariance to a combination of geologic factors that influenc e fault growth once faults extend beyond the confines of mudstone beds . Propagation of large faults across higher moduli opal-CT porcellanit e leads to a reduction in D/L, as does the development of drag folds. Further scatter in D/L occurs when fault tips splay as they approach d etachments. Large faults eventually merge into bedding plane detachmen ts, which originally formed due to flexural slip folding. Extremely hi gh D/L ratios are recorded for these merged faults as they accommodate block rotation within a simple shear zone. Thus, both mechanical stra tigraphy and the temporal evolution of fault systems can lead to a bre akdown in fault scaling relations thought to characterize isolated fau lt growth in a homogeneous medium. (C) 1997 Elsevier Science Ltd.