The attractor-based approach to damage evaluation of reinforced concrete pile foundations was studied based on shaking tests using a large scale laminar shear box. The following conclusions were reached: (1) The shape of the attractor of the structure acceleration during the aftershock differed from that during the foreshock. (2) The embedding dimension of the attractor of the pile acceleration during the aftershock was larger than that during the foreshock. This suggests that the piles during the aftershock behaved more probabilistic than that during the foreshock.