What was found
(CAN) ON APPROACH, APU WAS STARTED AS NORMAL. SHORTLY AFTER START UP A VIBRATION WAS FELT THROUGHOUT THE AIRFRAME. AUTO SHUTDOWN OF THE APU OCCURRED,AS WELL AS A FIRE WARNING IN THE COCKPIT. APU FIRE QRC WAS ACCOMPLISHED WITH ASSOCIATED FIRE HANDLE PULLED AND BOTTLES DISCHARGED - FIRE LIGHT WENT OUT. FLIGHT CREW DECLARED AN EMERGENCY AND CFR WAS CALLED OUT. AIRCRAFT LANDED WITHOUT INCIDENT. MAINTENANCE INSPECTION OF THE APU AND RELATED SYSTEMS REVEALED NO SIGNS OF FIRE OR DAMAGE TO MOUNTS,AS RESULT OF VIBRATION. AIRCRAFT GROUND CHECKED SERVICEABLE, APU WAS MEL'D (49-1) AND RETURNED TO SERVICE WITH NO FURTHER INCIDENTS TO REPORT. APU SCHEDULED FOR REMOVAL & REPLACEMENT ON 09 NOV.02