A ROCK BURST OCCURED IN THE 6020 RAMP (06 DOWN RAMP) WHICH REGISTERED 2.8 ON RICHTER SCALE. DAMAGE MAINLY TO RIGHT RIB. ABOUT 65' OF RIB, SOME BEYOND ANCHORAGE OF 4' SPLIT SETS. NO ONE WAS IN THE WORK AREA AT THE TIME OF THE BURST AND NO ONE WAS INJURED.