BEIJING, April 20 -- A quake measuring 6.3 on the Richter scale hit East China Sea at 8:26 a.m. Friday (Beijing Time), China's Seismological Monitoring Network reported.The epicenter, at 25.7 degrees north latitude and 125.1 degrees east longitude, was about 350 km to the east of Taipei and about 450 km from the nearest coastline of the Chinese mainland, the network said.