Earthquake was our fault
July 3, 2008 · Updated 3:59 PM
The island was shaken, but few were stirred when a magnitude 3.1 earthquake hit Central Whidbey Thursday morning.
The Pacific Northwest Seismograph Network reported that the modest temblor struck at 6:08 a.m. and had an epicenter on Plantation Drive, which is on the west side of Highway 525 south of Coupes Greenbank Store.
The earthquake was 19.9 miles deep.
The countys emergency dispatch center received a handful of calls about the earthquake, but no reports of damage.
Camera crews from Seattle TV stations scrambled around the island, but found few people with compelling stories to tell. Most of those heard or felt the earth shake thought it was more interesting than scary or dangerous.
Mary Coupe, owner of the Greenbank Store, said she woke up at about 5 a.m. and must have dozed off momentarily since she didnt feel or hear a thing. She lives on North Bluff Road, not far from the epicenter.
On the other hand, Vicki Plantz, the store clerk, was at home at Hancock Lake. There was a big sound, my windows shook for about three seconds and it was over, she said. I thought it was just a big boat.
Large ships traveling through Admiralty Inlet often make her home vibrate with their the giant motors. She thinks it might be because she lives on the a fault line.
Earthquake experts have identified a complex array of a dozen major fault zones in the Puget Sound, two of which run across Whidbey Island. Theres the North Whidbey Fault and the South Whidbey Fault. A fault is a fracture or zone or fracture in the rock strata.
The recent earthquake occurred on the South Whidbey Fault, which is a slightly unstable fault. According to a study by John Oldow of the University of Idaho for the the United States Geological Survey, the South Whidbey Fault exhibits documented reverse motion related to N-S regional shortening and (is) thought to have significant potential for large magnitude earthquakes.
On the other hand, the North Whidbey Fault that runs through Oak Harbor seems to be quiet. Oldow writes that theres no director evidence of recent activity along this fault line. Moreover, that lessens the risk of a giant, deadly earthquake caused by coordinated ruptures of the North and South Whidbey Island faults.
According to a report by Harvey Kelsey at Humboldt State University in California, scientists have found evidence of a major crustal earthquake along the South Whidbey Fault about 3,000 years ago. This displaced the two sides of the fault between three to six feet, with the north side becoming higher.
Kelsey measured the sea level difference at Crockett Marsh and Hancock Marsh. He wrote that the fault appears to be an asymmetric fold in the rock below.
Above ground, Whidbey Island folks are still chatting about the earthquake. Sheriff Mike Hawley, who lives in Freeland, thought it was a sonic boom. Jan Smith, the sheriffs spokesperson, lives in Clinton and was at home when the earth moved.
Smith said, laughing, that she was sitting in bed, drinking coffee and had a fat yellow cat on her lap.
I thought something had hit the side of the house, she said. There was no flickering lights, no falling pictures.
You can reach Jessie Stensland at firstname.lastname@example.org or 675-6611.