AN EARTHQUAKE MEASURING 5.1 ON THE RICHTER SCALE RATTLED NORTHEAST TAIWAN ON WEDNESDAY, BUT THERE WERE NO IMMEDIATE REPORTS OF CASUALTIES OR DAMAGE, OFFICIAL SOURCES SAID. THE EPICENTER OF THE QUAKE, WHICH STRUCK AT 3.21 P.M. (0721 GMT) WAS ABOUT 4.7 KM (3 MILES) WEST OF ILAN ON THE NORTHEAST COAST, AT A DEPTH OF 71 KM (44 MILES), THE CENTRAL WEATHER BUREAU SAID IN A STATEMENT.