A block model of distributed deformation by faulting

It is clear from palaeomagnetic evidence that large and hitherto unexpected rotations about a vertical axis are common in regions of distributed continental deformation. We propose a simple two-dimensional model to illustrate how fault movement and block rotation within a zone of distributed deformation may be related to the relative motion of the rigid plates that bound the zone. One surprizing feature of this model is that the component of strike-slip motion on the faults within the deforming zone is in the opposite sense to the strike-slip component across the zone as a whole. Thus slip vectors within the zone are not the same as that between the bounding rigid plates: in contrast to deformation at oceanic plate boundaries. Examples of active fault geometries similar to those of our model can be seen in Greece, Iran and the western USA.