REPRESENTATION OF TECTONIC STRESS

A diagram for the presentation of the stress tenser is proposed. The d iagram is an equal side triangle whose left side is labelled as [n(sig ma(1)-sigma(2))]/sigma(1), right side as [n sigma(2)-sigma(3))]/sigma( 1) and base as R. The R value is computed as the stress ratio of Etche copar et al. (1981); R = (sigma(2)-sigma(3))/(sigma(1)-sigma(3)). If s igma(1) = 1 and sigma(3) = 0, the remaining stress magnitude sigma(2) is equal to R. Left and right side of the triangle are scaled to fit p ositive infinite interval to a finite interval < 0, n >. Lines connect ing the same values indicated by a left side are parallel to the right side and vice versa. The base is proportionally calibrated to indicat e interval of R = < 0, 1 >. Lines connecting this calibration with the upper apex indicate stress ellipsoids with the same stress ratio, jus t progressively increasing the size of the greatest Mohr circle toward s the base. Line having the R value 0.5 indicates the plane stress. Li nes parallel to the left side show stress ellipsoids with the same sig ma(1)-sigma(3) values, progressively changing the R value. Left side i s a special line obeying in addition. sigma(2)=sigma(3), thus indicati ng the axial compression increasing towards the base. Lines parallel t o the right side show the stress ellipsoids with the same sigma(1)-sig ma(2) values, progressively changing the R value. Right side is a spec ial line obeying in addition sigma(1)=sigma(2) thus indicating the axi al extension increasing towards the base. Upper apex indicates the hyd rostatic stress state with all principal stress magnitudes equal. Grap h visualizes ellipsoidal shapes. The upper apex represents sphere and the line with R = 0.5 indicates ellipsoids with sigma 2(=)(sigma(1)+si gma(3))/2 Left and right apexes represent an ideal cigar and pancake s hape, respectively. points of the diagram to the right from the plane stress line show stress ellipsoids with control constriction points to the left from the plane stress control flattening. It is felt that th is diagram ignoring the volume effect by a putting ellipsoids into a f inite space provides a possibility either to compare the shapes of ell ipsoids or to study continuous mutual changes of the stress axes.