I don't think it's the same guy, Tom, although the Ballard cover matches my verbal description very well, there are some differences: there is a perspective view there, and the shapes are highly stylized objects and perhaps figures standing in a landscape with a vanishing point. Of course, artists do change their style, so it can't be ruled out that it's the same man.

In the art I remember the shapes were much smaller in size than the distances between the shapes, and there was no attempt at showing objects in the distance. I must have seen dozens of covers by this artist, all different, but all of exactly the same distinctive style. There is definitely an influence here, but if I had to bet on it, I'd say it's not the same man. I'll see what I can find on Richard Powers, although I suspect you'll get there first.