A strong earthquake with a preliminary magnitude of 6.6 shook the South Pacific island nation of Tonga on Monday, according to the U.S. Geological Survey. The quake occurred at 9:47 a.m. local time, with its epicenter located 198 kilometers north of the capital, Nuku’alofa, at a depth of 112 kilometers. The Hawaii-based Pacific Warning Center has issued no warnings of a potential tsunami. Tonga is situated on the Pacific “Ring of Fire,” a seismically active region that accounts for a large portion of the world’s earthquakes and volcanic eruptions.