A high-intensity earthquake measuring 7.8 on the Richter scale occurred in the sea off the east coast of Japan on Saturday, the USGS said.The quake struck 189 km west-northwest of Chichi-shima, and 874 km south of Tokyo, the US Geological Survey said. It said the temblor occurred at a depth of 677.6 km.Meanwhile, the India Meteorological Department (IMD) said the temblor struck at 4.53 p.m. at a depth of 660 km near Bonin Islands, an archipelago of over 30 sub-tropical and tropical islands, around 1,000 km south of Tokyo.