Constraining the strain ellipsoid and deformation parameters using deformed single layers: A computational approach assuming pure shear and isotropic volume change

If the deformation history of individual layers in a deformed rock mass can be appropriately analysed and categorised then the surface of no elongation (snoe) and the surface of no infinitesimal elongation (snoie) may be identified. A computational approach to automatically identify the polar snoe and snoie is presented and tested on synthetic and natural examples. Additionally the equations that allow extraction of parameter values, which quantify the deformation, are derived here. Two fundamental assumptions are made: 1) the progressive deformation is pure shear and 2) the associated volume change is isotropic. The proposed method is tested using data generated from known deformation sequences and is found to work reasonably well. However, as is the case with most methods of analysis, suitable data with a wide range of orientations is required for reliable results.