ALBERT

Description: Faults are important controls on hydrocarbon migration and ore mineralization and, in areas of active deformation, are the most important source of seismic hazard. However, faults are rarely discrete surfaces and the internal structure of fault zones (e.g., the thickness, nature and continuity of the fault rocks, the distribution and segmentation of slip surfaces, and the orientation, distribution and connectivity of subsidiary faults and fractures) is a key control on their bulk fluid flow and mechanical properties. This Special Publication was inspired by two sessions held at the European Geosciences Union General Assembly in Vienna during 2005 and 2006 and contains 19 original papers divided into three sections. Part I addresses the controls on fault zone evolution, whilst Parts II and III focus, respectively, on the mechanical behaviour and fluid flow properties of fault zones. The introductory paper (Wibberley et al.) addresses each theme of the Special Publication: fault zone evolution, the permeability structure of ancient and active fault zones, the impact of faults on hydrocarbon sealing and migration, and the implications of fault zone geometry and material heterogeneity for seismogenic processes. In each section, Wibberley et al. identify important recent findings and suggest areas in which new conceptual advances in our understanding of fault zones are likely to occur. A key theme highlighted by many of the papers in Part I is the importance of pre-existing mechanical heterogeneities (e.g., bedding, joints) in controlling the internal structure of faults in sedimentary sequences. Johanssen & Fossen consider the control of bed thickness and fault displacement on the geometry, orientation and distribution of minor fractures and deformation bands (i.e., the ‘damage zone’) that surround faults cutting aeolian sandstones, siltstones and shales in the western United States. They conclude that the highest concentrations of deformation bands occur close to the main ...