Though some Whidbey residents may have been jolted by the 3.3 magnitude earthquake in Penn Cove last week, or felt others that have been happening around the Olympic Peninsula recently, experts say there’s no cause for concern.
Harold Tobin, director of the Pacific Northwest Seismic Network, said most big earthquakes are not preceded by a cascading rise of smaller ones. A series of small quakes within the area is a fact of life in the Pacific Northwest, he said, and most are too small to feel until they get closer to the threshold of a 3.0 magnitude.
The quake near Coupeville, which happened at 7:47 p.m. on Wednesday, Jan. 17, had a depth of 55.8 kilometers, or 34.7 miles.
Joan Gomberg, a research geophysicist with the United States Geological Survey who specializes in earthquake seismology, was surprised to hear of the amount of people who felt the 3.3 shaker.
“Oddly enough, that was quite deep,” she said.
Both Gomberg and Tobin agree that there’s the potential for a bigger quake to be felt along the southern Whidbey Island fault, which stretches from Port Townsend to Woodinville. Gomberg said it’s possible that an earthquake on the fault could create a tsunami in Puget Sound if it displaces the surface underneath the water, known as the sea floor.
But the good news is that big quakes along the southern Whidbey Island fault seem to occur quite infrequently – once every 1,000 years.
And massive scale tsunami waves occurring in Puget Sound are also unlikely.
“These are really, really rare events and the chances of us having one in our lifetimes is small,” Tobin said. “It’s not zero though.”
He said it’s more likely that the next big shaker the region will feel will be like the 2001 Nisqually earthquake, which had a magnitude of 6.8. There is a recorded history of similar earthquakes happening between Seattle and Olympia in 1949 and 1965.
And as for “the big one,” otherwise known as the massive Cascadia subduction zone quake that we keep hearing is long overdue?
“I don’t think it will be Armageddon,” Gomberg said, adding that many of the news stories written about the quake tend to sensationalize it.
According to Gomberg, there is a 10% to 15% chance that the big one will happen within the next 50 years.
“I am very confident – and I’m not very confident about most things – that one day there will be a really big one here,” she said. “It’s going to be a major thing, without a doubt.”
Tobin advised people to be aware of earthquake hazards, such as bookshelves that aren’t fastened to walls or houses that aren’t connected to their foundations. Additionally, people living on bluffs may have to contend with landslide hazards.
“Be prepared, don’t despair,” he said.