SYDNEY, Oct. 21 (Xinhua) -- An earthquake of 6.4 magnitude struck roughly 54 km from the coast of Vanuatu around 2:00 p.m. local time (0300 GMT) on Monday, according to the U.S. Geological Survey.

The epicenter, with a depth of 226.08 km, was initially determined to be at 19.0408 degrees south latitude and 169.4528 degrees east longitude.

About 12 hours earlier, a smaller magnitude 4.5 tremor hit roughly 91 km off Vanuatu's coast.

No tsunami warning has been issued for either incident so far.