Mysterious Shudder, Earth
Tremor Shakes Kaua'i Residents

By Jan TenBruggencate
Science Writer
The Honolulu Advertiser - Hawaii's Newspaper

LIHU'E, Kaua'i - The earth shook on Kaua'i Thursday night, but no one is sure what caused it.
Residents from Ha'ena on the north shore to Wailua on the east side reported an extended shudder several seconds long that shook windows, walls and beds shortly before 8 p.m. Calls poured in to news media offices, police, civil defense and other county offices, the Navy at the Pacific Missile Range Facility and other agencies.
"Oh, my God! Our whole house shook, more than it ever has. We went downstairs to check whether things were OK," said Wainiha resident Barbara Robeson.
Princeville resident Donn Carswell said he felt a shaking about the same time.
"I felt a trembling and I thought I heard light thunder. It sounded like somebody was moving heavy sliding doors, but nobody was," he said. He thought it lasted less than 10 seconds.
Kaua'i Civil Defense officials said they received numerous calls, and the first thoughts were earthquakes and sonic booms, but they could confirm neither.
Agnes Tauyan, Navy public affairs officer, said neither the Navy at Pearl Harbor nor the Pacific Missile Range Facility had operations off north or east Kaua'i that could account for the tremors.
Donn Walker, Federal Aviation Administration regional public affairs officer, said there was no report in Honolulu FAA logbooks that might indicate a cause for the event. Tyler Johnson, Coast Guard 14th District public affairs officer, said the Coast Guard logs showed no activity at that time.
It could have been a small local earthquake, said Stuart Weinstein, geophysicist with the Pacific Tsunami Warning Center on O'ahu, but he said the center has no sensors on Kaua'i and could not detect any temblor from its O'ahu equipment.
"It wasn't large enough to trigger our alarms," he said. "I went back and looked at the screens, and it didn't get above the noise level."
Kaua'i gets few quakes. The Uniform Building Code has a six-level scale of the chance of ground shaking. The scale runs from 0 for virtually no chance of shaking, through 1, 2A, 2B, 3 and 4. Kaua'i ranks 1, just off being the least seismically active zone. O'ahu is only marginally more active at 2A and Maui County is 2B. The Big Island, one of the most earthquake-prone places in the world, ranks 4.
Some residents suggested distant thunder might have been involved, although the shaking was considerably worse than the noise.
"There have been thunderstorms around, but I didn't see anything on the radar maps over Kaua'i," said Pete Donaldson, National Weather Service meteorologist. "I couldn't see anything that would have produced thunder near Kaua'i."
Donaldson said it has been raining and that can lead to landslides. A check with tour helicopter firms that circle the island turned up no reports of major landslides in the island's interior, but cloud cover was heavy and much of the island was obscured.
Kapahi resident Louise Duval said the sound was not quite a sonic boom, not really an earthquake, but was enough to get her attention.
"It was strange. Strange enough that I went outside to check it out," she said.



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