Iselle was supposed to weaken as it slowly trudged west across the Pacific. It didn't — and now Hawaii is poised to take its first direct hurricane hit in 22 years. Tracking close behind it was Hurricane Julio, which strengthened early Thursday into a Category 2 storm.

As the two hurricanes churned toward the islands, an earthquake with an initial magnitude of 4.5 hit Hawaii's Big Island at about 6:30 a.m. local time, the U.S. Geological Survey reported.

The temblor struck on the north tip of the island, about 7 miles from Waimea.

About 15 to 20 miles from the epicenter, the quake felt like a quick shudder, very brief, but stronger than smaller quakes that sometimes hit the Big Island. There were no immediate reports of damage.

Meanwhile, state officials were assuring the islands are ready for the storms and people should prepare but not panic. Tourists on Wednesday tried to get in some last-minute beach time before the surf's up, but ugly. And residents are making bottled water tougher to find than a cheap fruity cocktail.

"Everybody says this is the last day of good weather, so we came down to the beach," said Shonna Snodgrass, a tourist in Waikiki visiting from Stafford, Virginia.

Travelers got their first word of disrupted flights Thursday, when commuter airline Island Air said it was canceling some afternoon flights between the islands and shutting down all operations Friday.

Hurricane Iselle was expected to arrive on the Big Island on Thursday evening, bringing heavy rains, winds gusting up to 85 mph and flooding in some areas. Weather officials changed their outlook on the system Wednesday after seeing it get a little stronger, giving it enough oomph to stay a hurricane as it reaches landfall.

"What ended up happening is the storm has resurged just enough to keep its hurricane strength," said Mike Cantin, a meteorologist with the National Weather Service.

Cantin said that means stronger winds of 60 to 70 mph, though rainfall estimates of 5 inches to 8 inches in a short time frame remained unchanged.

"Not a major hurricane, but definitely enough to blow things around," he said.

Iselle loomed about 400 miles east of Hilo early Thursday, with sustained winds of 85 mph and traveling about 18 mph.

Cantin said the Big Island's size and terrain would help break up the hurricane, weakening it into a tropical storm as it passes Maui and Oahu late Thursday and early Friday.

"The volcanoes on the Big Island will do a number on the system," he said.

Hurricane Julio, meanwhile, swirled closely behind with maximum winds whipping at 100 mph. The National Hurricane Center said it expected the storm to strengthen even more Thursday before gradually weakening by Thursday night. That weakening is expected to continue into the weekend.

Hawaii has been directly hit by hurricanes only three times since 1950, though the region has had 147 tropical cyclones over that time. The last time Hawaii was hit with a tropical storm or hurricane was in 1992, when Hurricane Iniki killed six people and destroyed more than 1,400 homes in Kauai, said meteorologist Eric Lau.

The two hurricanes have disrupted tourism, prompted flash flood warnings and led to school closures. Gov. Neil Abercrombie, meanwhile, signed an emergency proclamation allowing officials to tap into a disaster fund set aside by the state Legislature.

"The sole purpose is to see to it the health and safety of the people of Hawaii is first and foremost," Abercrombie said at a news conference surrounded by his cabinet members.

Hawaiian Airlines waived reservation change fees and fare differences for passengers who needed to alter travel plans Thursday and Friday because of the storms. Hawaiian Airlines spokeswoman Ann Botticelli said hundreds of inquires poured in from customers seeking to change their flights.

Some travelers remained hopeful.

Boston resident Jonathan Yorke and his wife booked a Hawaii vacation with their two daughters last year. He has been watching the news to see how the storms could affect the two-week trip to Maui and the Big Island.

"We're all optimists, so we'll make the best of it," Yorke said.

Washington state couple Tracy Black and Chris Kreifels made plans to get married in an outdoor ceremony on the Big Island Saturday. They spent Wednesday getting a marriage license, adjusting plans and communicating with worried guests on the mainland.

"We see the rain as a blessing," Black said. "It will work out as it's supposed to."

In Waikiki, Gwen Johnson wondered if she would make her flight home Thursday.

"We're leaving tomorrow and I'm a little concerned if we'll be able to get out with the turbulence and stuff," she said.

It wasn't immediately clear what financial impact the storms would have on the state's tourism industry, a key economic driver.

Hawaii residents also have had to adjust. Stores have seen long lines this week as people brace themselves.

Some are voting early in primary elections that close Saturday. The elections include several marquee races, including congressional and gubernatorial races. Abercrombie — who is running for re-election in a tight Democratic primary — said the election is expected to move forward as planned as of Wednesday afternoon.

Also, education officials said public schools on the Big Island, Maui, Molokai and Lanai will be closed Thursday.

The storms are rare but not unexpected in years with a developing El Nino, a change in ocean temperature that affects weather around the world.

Ahead of this year's hurricane season, weather officials warned that the wide swath of the Pacific Ocean that includes Hawaii could see four to seven tropical cyclones this year.

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Associated Press Writers Doug Esser in Seattle and Oskar Garcia in Honolulu contributed to this report.