The construction of shear strain profiles across brittle- ductile shears. Preliminary estimates of conventional shear strain rates for the Truchas and Palomares Shears ( Spain) and the Alpine Fault ( New Zealand).

A new method for determining the shear strain across and along brittle-ductile shear zones is introduced. It is used here to construct strain profiles for the Truchas and Palomares Shear Zones of Spain and the Alpine Shear Zone of New Zealand and to estimate the mean shear strains across them. The stratigraphical off-sets limit the period of shear motion so that mean shear strain rates of 2.6 X 10^-16 s^-1, 5.3 X 10^-15 s^-1 and 2.4 X 10^-15 s^-1 can be estimated for the Truchas, Palomares and Alpine shear motions, respectively. The examples are restricted to major wrench faults, but the methodology discussed here applies equally well to other types of shear zones of any size or orientation, e.g. below nappes, below lithospheric plates, shear motions in vertical direction and microscopic shear zones in cleavage fabrics.-Author