Displacement and strain

Agust Gudmundsson

doi:10.1017/CBO9780511975684.004

3 - Displacement and strain

Published online by Cambridge University Press: 05 June 2012

Agust Gudmundsson

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Agust Gudmundsson: Affiliation:
Royal Holloway, University of London

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Summary

Aims

This chapter gives an overview of the concepts of displacement and strain. In textbooks on structural geology, strain is normally treated in great detail. The reason is that strain, particularly finite strain, is of fundamental importance for understanding the kinematics of ductile deformation, such as occurs during folding. Here, however, the focus is on those aspects of strain that are useful when analysing stress-strain relations for brittle rocks, which to a first approximation behave as linearly elastic and are subject to small (usually less than 1%) strain. The main aims of this chapter are to:

Explain the difference between displacement and strain.
Provide examples of the use of each concept in geology.
Explain the difference between deformation and strain.
Discuss general aspects of infinitesimal strain.
Provide some basic formulas for measuring strain.
Discuss strain rates and how they are measured.

Basic definitions

Displacement refers to the change in position of a particle. When the displacement is very small, it is referred to as infinitesimal; when large, it is referred to as finite. Strain is also related to the displacement of particles from their original position to a new position. Strain and displacement are thus closely related. There is, however, a significant difference. Strain always involves changes in the internal configuration of the body. During strain, the distances between the particles that constitute the strained body change.

Type: Chapter
Information: Rock Fractures in Geological Processes , pp. 63 - 88

DOI: https://doi.org/10.1017/CBO9780511975684.004 [Opens in a new window]

Publisher: Cambridge University Press

Print publication year: 2011

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