April 9 (Bloomberg) -- The Pacific islands of Vanuatu and New Caledonia were shaken by a magnitude-7.5 earthquake, the largest temblor in the world so far this year, prompting a warning of a possible local tsunami.

The quake struck at 11:46 p.m. local time, about 89 kilometers (55 miles) south-southwest of Isangel in Vanuatu, and 174 kilometers northeast of Tadine in New Caledonia's Loyalty Islands, the U.S. Geological Survey said today in a preliminary report on its Web site.

The quake struck at a depth of 89 kilometers, less than two hours after a magnitude-6.4 temblor hit the same area. The Pacific Tsunami Warning Center said there was no threat of an ocean-wide tsunami, though a local event was possible.

``Earthquakes of this size sometimes generate local tsunamis that can be destructive along coasts located within 100 kilometers of the earthquake epicenter,'' the USGS said. ``Authorities in the region of the epicenter should be aware of this possibility and take appropriate action.''

The earlier temblor struck at 10:13 p.m. local time about 97 kilometers southwest of Isangel and 167 kilometers north- northeast of Tadine.

Until today's event, the year's largest earthquake was a magnitude-7.4 temblor that hit Indonesia on Feb. 20, killing three people and seriously injuring 25, according to data on the USGS Web site.

To contact the reporter on this story: Alex Morales in London at amorales2@bloomberg.net.

Last Updated: April 9, 2008 09:56 EDT