New Zealand earthquake holds lessons for Seattle
The city of Christchurch still hasn't recovered from a devastating 2011 earthquake that provides a glimpse of what could happen the next time the Seattle Fault rips.
Seattle Times science reporter
After Christchurch was hammered by an earthquake two years ago, New Zealanders found themselves groping for words to describe the devastation. So they fell back on the slang term “munted.” It means trashed, destroyed — and then some, said John Hare, a structural engineer from the battered city.
Seattle could be in the same predicament the next time the geologic fault that slices through Western Washington’s urban core snaps, Hare and other experts said Tuesday at a workshop on lessons from the Christchurch quake.
“Our earthquake will be worse,” Seattle City Councilmember Tom Rasmussen said after addressing the group. “The Seattle Fault runs right under our city.”
The death toll from the New Zealand quake was 185. A major quake on the Seattle Fault could kill nearly 10 times as many people, according to a 2005 analysis.
The fault, which scientists say passes under the city’s Sodo neighborhood and continues into the Cascade foothills, last ruptured about 1,100 years ago.
Total damage from the Feb. 22, 2011, Christchurch quake is estimated at about $30 billion — though the number keeps growing, said Kelvin Berryman of New Zealand’s Institute of Geological and Nuclear Science. With the second anniversary approaching, much of the city’s central core remains cordoned off, and nearly 70 percent of downtown buildings are being demolished.
“There’s almost nothing left untouched,” Hare said in an interview. He estimates it will be another three to five years before the central business district is fully functional again.
Christchurch’s historic neighborhoods, where lovely stone and brick buildings were reduced to rubble, will never be restored, said Rasmussen, who toured the city a year after the magnitude-6.3 quake.
“I came back committed to doing what we can here to prepare for an earthquake,” he said. Among Seattle’s recent initiatives is an inventory of nearly 800 at-risk brick buildings. The city is also considering an ordinance to mandate retrofits for those structures.
The steep economic toll in Christchurch has local engineers reconsidering the 2005 Seattle Fault study, which estimated economic losses of $33 billion from a magnitude-6.7 quake.
“I think we underestimated the cost and the recovery time,” said Mark Pierepiekarz, of MRP Engineering in Seattle. Based on recent quakes around the globe, full recovery would probably take a generation, he said.
The Christchurch quake knocked out electrical power and communications and did so much damage to water and sewer systems that it was several months before service was restored in some areas, said David Johnston, director of New Zealand’s Joint Centre for Disaster Research.
Schools were closed for six weeks or more. But 95 percent of the city’s businesses are still in operation, and reconstruction work is buoying the local economy, Berryman said.
The quake struck on a previously unknown fault and in an area that wasn’t considered at high seismic risk. Shaking was twice as strong as most buildings were designed to withstand, said Hare, of Holmes Consulting.
More than 11,000 aftershocks, some as big as magnitude 6, have rattled nerves and delayed rebuilding.
But New Zealand’s recovery will be aided by the fact that nearly 80 percent of losses from the quake were insured. In the Pacific Northwest, only about 12 percent of homeowners carry earthquake coverage, Rasmussen said.
The Pacific Northwest is more seismically active than Christchurch, and is vulnerable to three types of earthquakes: deep quakes, like the 2001 Nisqually quake; coastal megaquakes and tsunamis, like the one that struck Japan in 2011; and shallow quakes on a network of faults that crisscross the Puget Sound Basin and include the Seattle Fault, the Tacoma Fault and several others.
Geologists estimate the region gets slammed with a shallow quake every thousand years, on average. Estimated at magnitude 7 or more, the most recent Seattle Fault quake lifted beaches 20 feet in West Seattle and on Bainbridge Island and triggered a tsunami in Puget Sound.
“Our risk is huge,” Rasmussen said.
The Christchurch workshop was held in conjunction with the annual meeting of the Earthquake Engineering Research Institute, which is bringing more than 300 seismic researchers and engineers to Seattle this week.
Sandi Doughton at: 206-464-2491 or email@example.com