TOKYO: A powerful 7.0-magnitude earthquake struck off the southwestern coast of Japan early Saturday, authorities said, with a small tsunami observed on one island but no major damage reported. The US Geological Survey (USGS) put the epicenter of the shallow quake about 160 kilometers (100 miles) from the town of Makurazaki in southwestern Japan. It was centered about 10 kilometers under the ocean floor and struck at 5:51 a.m. (2051 GMT Friday), the USGS and Japan’s Meteorological Agency said. The Meteorological Agency issued a tsunami advisory as a result of the quake but cancelled it about 90 minutes later. No major damage from the quake or tsunami was reported, while a pair of nuclear reactors on the southern island of Kyushu were unaffected, its operator said.