Strain analysis from point fabric patterns: An objective variant of the Fry method

A simple technique is devised for obtaining finite strain estimates from deformed patterns of points possessing anticlustered properties. As an alternative to the Fry approach where analysis is carried out in the deformed state, the new method performs a large number of trial de-strainings of the point pattern. For each de-strained dataset, a statistical analysis tests for the assumed properties of the point fabric in the pre-deformational state, that the points come from an isotropic but non-Poisson distribution. This computer-based procedure usually yields a number of acceptable solutions for the possible strain ellipse in the given geological situation. The variability of the strain estimates for a given dataset provides an assessment of the precision of the strain results.Testing of the method with both synthetic and real datasets suggests that a best estimate for the strain ellipse is one corresponding to the centre of gravity on the Elliott strain plot. The performance of the new method compares favourably with existing Fry methods.