Shallow New Zealand quake a warning to Pacific Northwest

Experts in the northwest have warned that the catastrophic earthquake in New Zealand is akin to what could happen in the United States.

The quake struck Christchurch, New Zealand, a city the size of Spokane, along a fault line that had been undetected until late September. That's when an even bigger quake struck New Zealand, but it only caused minor damage because it was situated far away from any major cities. The death toll was expected to grow to 300, according to officials in Christchurch.

Scientists have discovered evidence of shallow faults in the northwest in recent years, such as the Seattle fault, which runs beneath Qwest Field and closely follows Interstate-90.

"In reality, there's one for every municipality," says John Vidale, director of the Pacific Northwest Seismic Network and professor at the University of Washington. "There's the Tacoma fault, the Olympia fault, the Portland hills fault, and the south Whidbey fault, which runs up the east side of Puget Sound," he says.

These shallow faults, like those in New Zealand, tremor only seldom - perhaps once every 1,000 years or even once every 10,000 years. Although uncommon, it is exceedingly lethal.

The Nisqually earthquake, on the other hand, was the most recent big earthquake in western Washington. On Monday, the tenth anniversary will be celebrated. It was ten times the size of the one in New Zealand, but it was buried ten times deeper.

Here's an example of a comparison:

Earthquake in Christchurch, New Zealand, on February 22, 2011:

6.3 magnitude, 3.1 mile depth
12:51 p.m. is the current time.

The Nisqually earthquake struck on February 28, 2001.

Depth - 32 miles Magnitude - 6.8
10:54 a.m. is the time of day.

According to preliminary estimates, the forces felt on the ground in New Zealand would have been three to four times stronger than the worst shaking from the Nisqually quake.

Vince Stricherz of the University of Washington has posted an excellent look back at the Nisqually earthquake and some lessons learnt since then. For example, we now have more accurate maps of which neighborhoods pose the greatest threat, and more older structures have been fortified.

Nonetheless, the damage in a city with current building rules (as opposed to a city like Port-au-Prince, Haiti) should serve as a wake-up call in Seattle, Portland, and everywhere in between.

"I believe the damage would be bigger here than in New Zealand," Vidale says, "since we are much more built up and have a lot of ancient things erected before we knew we had significant earthquakes here."

Simple precautions, such as tying down your water heater, fortifying your chimney, and having an emergency bag and a plan, are recommended by disaster planners.

Earthquake News

Shallow New Zealand quake a warning to Pacific Northwest

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