NZ quake, a warning to North America?

New Zealand flag
Washington, Feb 23: The terribly destructive New Zealand earthquake that killed dozens and caused heavy damage is a warning to cities up and down the West Coast of North America, according to a researcher.

Even though Tuesday's 6.3-magnitude earthquake was weaker than last year's event, it was much shallower, was situated directly under Christchurch, hit during the lunch hour when more people were exposed to damage, and shook sediments that were prone to 'liquefaction', which can magnify the damage done by the ground shaking.

The 7.1 magnitude earthquake that struck the nation last September near the same area killed none.

Robert Yeats, a professor of geology at Oregon State University and an international earthquake expert, said that same description matches many major cities and towns in Washington, Oregon, California and British Columbia.

"The latest New Zealand earthquake hit an area that wasn't even known to have a fault prior to last September, it's one that had not moved in thousands of years. But when you combine the shallow depth, proximity to a major city and soil characteristics, it was capable of immense damage," said Yeats.

"The same characteristics that caused such destruction and so many deaths in Christchurch are similar to those facing Portland, Seattle, parts of the Bay Area and many other West Coast cities and towns," he said.

"And it's worth keeping in mind that New Zealand has some of the most progressive building codes in the world. They are better prepared for an earthquake like this than many U.S. cities would be," he added.

According to Yeats, the risks from comparatively shallow 'crustal' faults are often given less attention compared to the concerns about the major subduction zone earthquake facing the Pacific Northwest in its future, or other major quakes on famous plate boundaries such as the San Andreas Fault.

Associated with that is the risk of liquefaction - the characteristic of some soils, particularly sediments deposited over long periods of time, to become saturated with water and quiver like a bowl of gelatin during an earthquake.

Such motions can significantly increase building damage and loss of life.

Like much of the West Coast, Yeats said, New Zealand sits near a major boundary of the Earth's great plates - in this case, the junction of the Australia Plate and the Pacific Plate.

Despite intensive seismic studies in that nation, no one had yet identified the related fault that devastated Christchurch.

"We can learn about earthquakes and help people understand the seismic risks they face But it's still an inexact science, the exact timing of an earthquake cannot be predicted, and the best thing we can do is prepare for these events before they happen," said Yeats.


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