Residents from Kaua'i to the Big Island were rattled from their morning routines yesterday by a one-minute earthquake that caused homes to creak and cars to rock, yet for many people registered as barely a shudder.

"I was sitting at a red light on South Kihei, and the car shook back and forth. That impressed me," said Charlotte Hepler, a Kihei, Maui, resident who felt the quake in her car.

The quake, which originated in the Earth's crust 5 miles below the ocean's surface between the Big Island and Kaho'olawe, shook the island chain from one end to the other at 10:03 a.m. yesterday.

Some people felt two distinct shudders, others a firm jolt like an impact.

"The boards started creaking in the house. I've never heard that before in 20 years," said Alan Lloyd of Lanikai.

Four blocks from the beach in Kailua, Betty Lou Nobriga was talking on the phone. "I felt my house move," she said.

Terrence Aratani, of Salt Lake, was working on the second floor of the State Capitol building. He said most of his co-workers didn't notice it, but his experience living in California helped him recognize the quake.

"I could feel it coming from underneath, and I knew right away it was an earthquake. Then I could hear the ceiling tiles shake," Aratani said. "You could hear the rumble."

The shaking was barely discernable on Kaua'i, but Kaua'i resident Greg Shepherd, a music professor at Kaua'i Community College, was perhaps in the perfect position to feel it.

"I was meditating on my concrete floor in Wailua Homesteads. It was faint, but the thought went through my mind that it might be an earthquake," Shepherd said.

At Kaluako'i on Moloka'i, Edie Anderson said she was working at her computer and felt a mild vibration that her husband didn't notice, and it didn't wake up her dog.

Other Hawai'i residents from the Big Island to O'ahu reported the shaking felt like an unbalanced load was rocking the washing machine, like a truck hit the house or a big truck rumbled by the house, and like an oceanic rolling.

The U.S. Geological Survey's National Earthquake Information Center established a strength of 4.5 for the quake, roughly between the initial estimates of 5.0 by the Pacific Tsunami Warning Center at 'Ewa Beach, and 3.8 by the Hawaiian Volcano Observatory on Kilauea Volcano, Hawai'i.

In deep water at the foot of the Mahukona volcano that runs out from the northwest side of the Big Island, the site of the shake was 5 miles deep in the Earth's crust, at a point roughly west of Hawai'i Island's northernmost point and south of Kaho'olawe.

Hotel security officer Tim Haverly said he was concerned about the significant difference in reported strengths.

"This time, no harm, no foul, but next time? This is a big difference. This could cost lives someday," Haverly said.

Stuart Weinstein, assistant director of the Pacific Tsunami Warning Center, said the numbers are different largely because the agencies are looking at different data and working with different scales. The warning center's 5.0 was calculated as what is called local magnitude. The USGS 4.5 is worked out from a scale called body wave magnitude.

The volcano observatory's calculations are tuned to much smaller earthquakes, while the tsunami warning center's scale is designed to pick up potentially destructive, tsunami-generating quakes, Weinstein said.

"They're different because the organizations have different missions," he said.

State Civil Defense authorities focus on a single number: The one they get from the Pacific Tsunami Warning Center, said Dave Curtis, public relations officer for State Civil Defense.

The first thought of some residents was that yesterday's shaking might have generated a tsunami. It did not, but Civil Defense officials were pleased that so many people were alert, and used it as an opportunity to remind residents of low-lying areas that locally generated tsunami can hit within minutes of a severe quake.

"An earthquake that generates a tsunami is an event that can happen 24 hours a day, seven days a week. The moment you feel the shake, if you're in one of the (tsunami inundation) zones, don't wait for the Civil Defense sirens. Get your readiness kit and evacuate," Curtis said.

Pacific Tsunami Warning Center geophysicist Gerard Fryer said the quake was most likely the result of a settling or adjustment of the Earth's crust to the weight of the Hawaiian Islands.

"There are not usually aftershocks from these events," he said.

Too, at a magnitude of 5.0 or less, they are unlikely to generate a tsunami. Fryer said "you'd have to get up into the 6's before you get a tsunami."

Reach Jan TenBruggencate at jant@honoluluadvertiser.com.