BY DEAN KAHN:
Rebekah Paci-Green, an earthquake-damage expert at Western Washington University, says emergency-response experts in the U.S. have worried most about two scenarios.
One was a major hurricane hitting New Orleans. Check that one off the list, although it could happen again.
The other scenario? A massive earthquake along the Cascadia Subduction Zone, the 700-mile fault off the Northwest coast from Northern California to the northern part of Vancouver Island.
A large Cascadia quake and tsunami could kill more than 14,000 people in the region and cause more than $80 billion damage. In comparison, Hurricane Katrina, the first scenario, killed 1,800 people and did $150 billion damage.
Paci-Green is director of the Resilience Institute at Western. With a doctorate in structural engineering and years of seismic-safety research and fieldwork, she was a logical choice to write “Cascadia Rising,” a report that estimates deaths, injuries and destruction from a magnitude 9.0 quake and tsunami on the Cascadia fault.
She will be the keynote speaker at a free Bellingham meeting Saturday, Jan. 23, about the impact of a major quake in the Northwest and what people can do to prepare. For details and reservations, call 360-734-3215 or go to WhatcomVolunteer.org/Disaster.
Tectonic clash
A “subduction zone” is where a tectonic plate - a plate of the Earth’s crust - slides beneath another one. Along the Cascadia fault, a plate to the west is sliding under the North American plate. When pressure causes the fault to rupture, you have an earthquake, maybe a big one.
The world’s largest quakes happen along subduction zones, with the largest on record the 9.5 monster off the coast of Chile in 1960. Such quakes shake for a long time, trigger large tsunamis and have numerous aftershocks.
“Most of us will get very, very tired of the aftershocks and the shaking,” Paci-Green said.
The Northwest sits on the seismically active “Ring of Fire” lining the the Pacific Ocean. Small and modest quakes hit the region all the time, including a 4.8 quake on Dec. 29, 2015, that was centered north of Victoria, B.C., and was widely felt across Whatcom County.
A recent sizable Northwest earthquake was the 6.8 quake in February 2001 that centered near the Nisqually Delta, northwest of Olympia. The ground shook for 40 seconds, causing more than $1 billion damage, injuring about 200 people and contributing to the death of a woman who suffered a heart attack.
“Cascadia Rising” posits a 9.0 quake centered 95 miles west of Eugene, Ore. Chances are a quake along the fault will be smaller, but there’s an estimated 10 percent chance of it being even larger.
A 9.0 quake would release nearly 2,000 times more energy than the Nisqually quake. That doesn’t mean the shaking would be 2,000 times stronger, but the area affected would be much larger, and the shaking could last four to six minutes.
Evidence suggests that subduction zone quakes in the Northwest occur every 500 years, on average. The last one was 300 years ago, so the next one could be two centuries from now. Or tomorrow.
During a 9.0 quake, land along the Washington and Oregon coast could drop more than 6 feet.
Shaking ground will cause its own death and destruction, but the resulting tsunami likely will claim most of the victims as it sweeps over coastal communities like Ocean Shores and Long Beach. A quake during the summer, when the state’s beaches and parks are busy, could result in additional deaths.
Whatcom impact
Hollywood disaster movies like to portray quakes that level communities to piles of rubble. That might happen in, say, rural Nepal, but most buildings in Whatcom County will remain standing after a 9.0 quake, Paci-Green said. However many buildings might be unusable or too expensive to repair.
Whatcom County’s distance from the Cascadia fault, plus the buffer of Vancouver Island, means a tsunami won’t cause the kind of harm locally that will devastate the coast, she said. And there might not be many fatalities in the county if people on sidewalks avoid bricks and other material falling from old masonry buildings, such as those in Fairhaven and along Railroad Avenue, she said.
That doesn’t mean life will be easy in the early days. Aftershocks can further damage weakened buildings. Power blackouts could last days, even months. Communications could be out for days. Landslides might occur. Broken gas lines could fuel fires, with busy emergency-responders slowed or stymied by damaged roads and bridges.
A quake during winter, when it’s cold and wet, will add to the misery.
The long-term picture isn’t pretty, either. Damage to highways, bridges, ports and airports along the I-5 corridor will slow the delivery of supplies and other help. The region’s economy will suffer; some businesses and residents might decide to move.
“It’s not going to be particularly pretty,” Paci-Green said. “It’s a long slog of recovery.”
KNOW THY NEIGHBOR
Along with food, water, medicine and other supplies, residents’ plans to survive an earthquake should include knowing their neighbors, said Rebekah Paci-Green, director of the Resilience Institute at Western Washington University.
The same way that people in Block Watch programs work together to reduce crime, residents who know their neighbors can check on each other once the ground stops shaking, and can help them turn off their gas lines and take other safety precautions.
Movies like to show people turning to the “law of the jungle” after a disaster, but most communities respond with cooperation and kindness, Paci-Green said.
“Strong communities are going to do better,” she said.
www.bellinghamherald.com
No comments :
Post a Comment