The powerful earthquake off Chile also sparked a tsunami advisory for part of coastal California and Hawaii, prompting officials in both states to urge caution around shorelines.

The Pacific Tsunami Warning Center first issued a more serious tsunami watch for Hawaii shortly after Wednesday's magnitude 8.4 earthquake. Officials later downgraded that to an advisory, saying that no major tsunami was expected in the state.

But they warned that sea-level changes and dangerous currents could pose a threat to those in or near the water.

The center estimated that the effects from the tsunami would arrive in Hawaii about 3 a.m. (6 a.m. PDT) Thursday.

The Honolulu Department of Emergency Management said people should stay out of the ocean from 3-7 a.m., and the U.S. Coast Guard urged caution.

"The public is advised to use extreme caution and prepare for a tsunami wave forecasted to generate strong currents and surf throughout the main Hawaii Islands," the Coast Guard said.

A similar advisory was issued for southern and central California, affecting about 300 miles of coastline stretching from the southern end of Orange County to most of San Luis Obispo County on the central coast.

The possible changes associated with the advisory are expected to hit first in the south at about 4:45 a.m. PDT Thursday and move north in the minutes that follow.

Authorities in California called on people to refrain from waterfront activities.

"The tsunami waves may rise less than one foot in height, but there is a possibility of a surge of waves and currents that may impact the Los Angeles County beaches and harbor areas," the county Office of Emergency Management said.

A tsunami warning was last issued for Hawaii in 2012, after a powerful earthquake off the coast of Canada. The Pacific Tsunami Warning Center lifted its tsunami advisory three hours after downgrading from a warning and less than six hours after the waves first hit the islands. The state was spared from severe surges.

__

Associated Press Writers Audrey McAvoy in Honolulu, Andrew Dalton in Los Angeles, and Bob Seavey in Phoenix contributed to this report.