(Changes dateline, updates with damage estimates, quotes)

CANBERRA, Aug 2 (Reuters) - A powerful magnitude 7.3 earthquake rattled the Pacific nation of Vanuatu on Thursday, cracking roads and disrupting power supplies, but did not cause major damage, local authorities said.

The quake occurred at 0409 locally on Thursday (1709 GMT Wednesday) about 45 km (30 miles) southeast of the central island of Santo at a depth of around 150 km (90 miles) below the Pacific Ocean surface.

"It's a pretty good size, but it's deep and there is no tsunami threat. It's aways out to sea," Geophysicist Robert Cessaro at the Hawaii-based Pacific Tsunami Warning Center told Reuters.

Jesse Benjamin, a spokesman for the Vanuatu government meteorological office, said the quake was felt strongly on Santo.

"There are cracks in the roads, cracks in the offices, the power went down and computers, but we do not expect major damage," he said from the capital Port Vila.

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