Faults

Abstract

This chapter takes you to the amazing world where a block of rock mass moves past another such block along a plane of separation called fault. A fault is an elongated zone of high shear stress along which two blocks of adjacent rocks have been offset. It is thus a discontinuity or anisotropy due to which the rock loses its cohesion. Being a plane, a fault can be described in geometric terms such as dip and strike. The orientation of stresses acting upon a fault surface controls the geometry of the fault. Rubbing of two blocks of rock masses not only leaves behind a variety of signatures on or in close vicinity of the fault surface but may also genetically modify the host rocks. During fieldwork, a geologist is sometimes surprised to note that in some areas a fault has concealed one or a few beds while in other areas it has got a few other beds repeated. In brief, a fault is able to do or undo many things to the rocks of an area that sometimes leave a field geologist baffled!

In this chapter, the reader may find a detailed description of faults in respect of their geometrical attributes, classification, recognition in field, common rock types found in fault zones and mechanics of faulting. Faults are highly useful structures in the exploration of hydrocarbon, minerals and groundwater. The reader can get all these and many more once he/she takes a plunge into this chapter!