A COMPUTER-PROGRAM FOR THE CALCITE STRAIN-GAUGE TECHNIQUE

The calcite strain-gauge technique has been used successfully to deter mine strains in slightly to moderately deformed limestones. The techni que involves the use of a universal stage to collect calcite twin orie ntation, thickness and frequency data. The data are reduced by a least -squares method to give the orientations and magnitudes of the princip al strains. The purpose of this paper is to describe an easy-to-use co mputer program for the technique, and an accompanying manual on collec ting data for the strain-gauge analysis. The program calculates princi pal strain magnitudes and orientations, total strain due to twinning ( J2(0.5)), standard errors for the strains, average twin-width, twin in tensity and percent negative expected values. In addition, the program can plot stereonets with compression axes, tension axes, poles to e t win planes, crystallographic c-axes, g-axes, average twin-widths per t win set, twin intensity per twin set, and positive and negative expect ed values. The stereonets may also be rotated. All calculated orientat ion data may be saved in a computer file for later input into a stereo net contouring program. The user may choose automatically to remove 20 % of the twin sets with the largest deviation, or manually to remove s elected twin sets from the data being analyzed, in order to 'clean' th e data. Twin sets that give positive or negative expected values may a lso be analyzed separately.