A B757-200 flight crew experienced high vibration levels on the right engine. They coordinated with Dispatch and Maintenance; declared an emergency; and returned to their departure airport.

Narrative

Departing ZZZ on climbout; approaching FL350; noted a vibration in the floor of the flight deck associated with #2 engine. Use of Right Engine Anti-ice did not improve our situation. We were cleared to climb to FL390; however; approaching FL370 #2 engine; still producing climb power; began to register an N1 vibration of amber 2.8 confirmed by hull vibration felt by Flight Attendants and passengers. A radio call to Dispatch turned into a 3-way conference call with Maintenance. Real time engine monitor revealed that soon we would be thrust limited by the N1 vibration on the right engine. We declared an emergency with ZZZ. ZZZ Center cleared us to descend and return to ZZZ. Returning from this point allowed us to make an idle power descent back to ZZZ. ZZZ Airport Crash Fire Rescue equipment met our flight for landing on Runway XX. One vehicle remained with us from landing until we reached our gate where we terminated our emergency. Maintenance met our flight; reviewed a 'Saved Event Record' of the right engine parameters inflight; took the aircraft out of service.