These are results of Repeated Magnification and Probing algorithm for generating artificial terrain. The algorithm itself is pretty basic, and the results are pretty much basic height maps. But these can be used as base maps for erosion algorithms to produce nice realistic results.
The work was published as,
Repeated Magnification : a New Approach to Generating Artificial Mountain like Terrain 4th International Conference on Computer Graphics and Interactive Techniques in Australasia and Southeast Asia ( GRAPHITE 2006 ) Kuala Lumpur, Malaysia