Thanks for the post and pictures.

There's no reason one stone can move much more than another while being shaken in an earthquake. There are a lot of complex forces at play and the results will usually be chaotic in part and in whole.

I'm very impressed by the streaking I'd never seen before and was not aware of. Of course my first guess is that it's a complex iron molecule called siderite which was saturated in the water used to lift the stones.