Kenneth M. Cruikshank
Fractures: Introduction

Schematic drawing illustrating the three fundamental modes of fracture. A: mode I, tensile or opening mode; B: mode II, in-plane shear or sliding mode; C: mode III, anti-plane shear or tearing mode. For a "fault" you will have edges that will be mode II fracturing, and edges that will be mode III. Only in a joint will you have all of the perimeter being the same mode of fracturing (mode I).

Atkinson, B. K., Ed. (1987). Fracture mechanics of rocks. London, Academic Press.

Coordinate frame for analyses of linear elastic crack tip stress field. A mode I (tensile crack or joint) is shown as an example. The opening of this crack is exaggerated as the sharp-slit approximation is an integral part of the linear elastic analysis. Rectangular and polar coordinate compoents are shown, e.g. x,y,z, and r, q, respectively at the crack front.

Atkinson, B. K., Ed. (1987). Fracture mechanics of rocks. London, Academic Press.