In Part I of this series, we look at the geometric representation and identification of faults. In the final part, we review slip classification, stress orientations and tectonic styles of faults.

Part II: In the first part of this feature, we looked at the geometric representation and identification of faults. In this concluding article, we review the slip classification, stress orientations and tectonic styles of faults.

Rock folds are found in various shapes and sizes on Earth, and people are often amazed to see how large blocks of hard rocks have been folded like ocean waves. But fascination with folds is also shared by the petroleum industry. In Part I of this two-part article we unfold rock ‘folds’ to better understand their geometry and genesis.

The Alps, the Himalayas and other similar high mountains on Earth owe their existence to a series of giant rock folds. But how do stiff, solid rocks fold?

Rock fractures are ubiquitous because rocks in the Earth’s upper crustal levels are brittle. However, the fractures show considerable variations due to their origin, geometry and rock properties. Given the petroleum industry’s major shift in recent years to exploit tight reservoirs, there is now greater interest in rock fracture studies because open fractures, whether natural or hydraulic, provide the essential permeability for fluid flow in such reservoirs. A fresh understanding of rock fractures is thus timely. In this two-part article, we first review the geometry and characteristics of rock fractures. In part two, geomechanics of fractures will be discussed.

How and why do fractures occur in rocks?