Geometric controls on the evolution of normal fault systems

Abstract

The growth of normal fault arrays is examined in basins where sedimentation rates were higher than fault displacement rates and where fault growth histories are recorded by thickness and displacement variations within syn-faulting sequences. Progressive strain localization is the principal feature of the growth history of normal faults for study areas from the Inner Moray Firth, a sub-basin of the North Sea, and from the Timor Sea, offshore Australia. The kinematics of faulting are similar in both study areas. Fault displacement rates correlate with fault size, where size is measured in terms of either displacement or length. Small faults have higher mortality rates than larger faults throughout the growth of the fault system. Displacement and strain are progressively localized onto the larger faults at the expense of smaller faults at progressively larger scales. Strain localization and the preferential growth of larger faults are attributed to geometric factors, such as size and location, rather than to the mechanical properties of fault rock in individual faults. This conclusion is supported by numerical models that reproduce the main characteristics of fault system growth established from both study areas.

Evaluating hydrocarbon trap integrity during fault reactivation using geomechanical three-dimensional modeling: An example from the Timor Sea, Australia

“…For the Jurassic reservoir-bounding fault planes with dips of 60 to 65°(consistent throughout the modeled area), the amount of extensional deformation (heave) can be estimated as proportional to the accumulated throw. As expected from results from Zhang et al (2009) and previous empirical observations and numerical models (Cowie, 1998;Walsh et al, 2001;Meyer et al, 2002;Gartrell et al, 2006), a strong correlation between initial fault length and the amount of accumulated throw during extensional reactivation exists. Larger faults (F1, F4, and F5) accommodated most of the extensional deformation, reflected as higher throws The height of the larger faults F1, F4, and F5 was initially set so that they reached the top surface (i.e., maximum possible height); this parameter most probably influences the outcome of the modeling (see below) in addition to the other major control from the fault strike lengths.…”

The nature and tectonic significance of fault-zone weakening: an introduction

“…Our improving understanding of the scaling relationships between fault attributes such as length, width, magnitude of displacement and interconnectivity suggests that these factors will additionally influence the processes of fault growth and reactivation (e.g. Cowie & Scholz 1992;Somette et al 1993;Walsh et al 2001).…”

Rapid spatiotemporal variations in rift structure during development of the Corinth Rift, central Greece

“…Studies of these evolving and mature rifts have recognized progressive strain localization as an important process in rift evolution on a variety of temporal and spatial scales. It is commonly thought that rifts develop an initially broad zone of complex deformation that becomes localized onto a smaller number of discrete and increasingly large faults [ Walsh et al ., ; Cowie et al ., ], while sedimentation becomes focused into fewer, larger depocenters [ Gawthorpe and Leeder , ; Gawthorpe et al ., ; Cowie et al ., ]. Furthermore, it has been shown that active faulting and strain migrate toward the rift axis with increasing extension, resulting in rift narrowing [ Gawthorpe et al ., ; Cowie et al ., ].…”