We present examples on the scale of several meters which we obtained in the central part of the massif along the Cap de Long. The 200 FF bill in the lower left corner serves as scale. We present in this paper a numerical simulation of the shear bands of elasto-plastic materials on different scales and calculate their fractal properties. We also measure for the first time in the field the fractal dimension of shear bands in granodiorite formed under confining pressures of around 5 kbars. It is well known from experiments that rocks increase in volume, they dilate, when distorted by shear.
Dilation occurs by tensile cracking and is necessary to lift sliding blocks over asperities.
This gives the plastic flow rule which besides the yield criterion characterizes the type of plasticity. Since our initial setup was completely homogeneous the random nature of the shear bands is due to minute effects in the round-off of the floating point numbers in the computer. These round-off errors only trigger the initial position of the shear bands but have no influence on the further evolution of their pattern. We checked this by simulating a system with weak quenched disorder and found the same result as in the homogeneous case. The only difference between these two simulations was that localization in the homogeneous case started later than in the inhomogeneous case.