Ground resonance is a term we misuse the way we misuse LTE and Settling with power. Every time a guy runs close to pedal limits he calls LTE, every time he starts falling through on approach it is VRS and every time the aircraft wiggles on the ground it is ground resonance.
Some thoughts on true ground resonance:
1) It is possible to get it in any aircraft that has a lag degree of freedom, even the 412.
2) It takes something mis-adjusted or mis-maintained to get it, because all helos that have lag hinges have systems to quell it. Manufacturers have to prove they are immune to ground resonance to themselves and to the FAA. Those systems (oleos, dampers on skids, dampers on blades, elastomers on all the previous) do not cause ground resonance, they prevent it.
3) It is a destructive resonance where the blade goes out of lag position, and the ground restraint (gear, skids, chocks/chains) reflects the out of balance back to the rotor in such a way as to drive the blade further away from the center. This means the vibration amplifies with each cycle.
4) True ground resonance is fast, vicious and destructive. Usually the number of cycles is few (maybe 10 seconds) and the cure is to leap airborne (stops the ground from reflecting the wave back to the head) or shut down fast, slapping on the rotor brake (which drives all the blades forward and again breaks the cycle).
5) Some helos have spots where the main rotor dampers are less effective (sweet spots in the cyclic) while on the ground, and they shuffle or bounce in yaw, roll or pitch enough to be noticed by the crew. These areas of lower damping are not ground resonance.