We investigate the footprints left over by SiGe islands epitaxially grown on Si(0 0 1) substrates at temperatures between 620 and 740 degrees C by using a combination of selective wet chemical etching and atomic force microscopy. Dislocated islands (superdomes) exhibit rather complex footprints consisting of circular "tree-ring" structures. A simple phenomenological model is able to describe the formation of the ring like structures. Coherently strained islands are observed to move away from the nearby superdomes preserving their shape, while coherent islands located a few tens of nanometers away from the closest superdomes do not move. The lateral island motion is triggered by the strain repulsion produced by the growing superdome and leads to an asymmetric alloying of the moving island. (c) 2006 Elsevier B.V. All rights reserved.