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What Seismologists Have Learned About The Wasatch Fault Since The Magna Earthquake

SALT LAKE CITY, Utah – One year ago Thursday, a magnitude 5.7 earthquake with an epicenter near Magna rattled the Wasatch Front, and it is still revealing new information about the Wasatch Fault.

That quake was the largest to rattle Utah in nearly 30 years. It was followed by a couple of magnitude 4.6 aftershocks and hundreds of smaller aftershocks that still continue.

Keith Koper, director of the University of Utah Seismograph Stations, characterized that earthquake as moderate-sized, but large for Utah. Scientifically, it was beneficial and even helped the seismologist understand his work better.

“It was definitely the strongest shaking that I’ve ever felt from an earthquake,” said Koper.

He knew what it was right away because he had felt minor quakes before, but never a moderate 5.7. Suddenly, he said, his life’s work felt more real. “It gives me a little more empathy, too, for how really dangerous and sort of shocking it is, and scary it is to go through something like that,” he said.

In spite of the damage it caused for businesses and residents in Magna, it provided a wake-up call for preparedness without causing communitywide catastrophic damage.

“Many people are never going to forget that,” Koper said. “People that went through it who went through it here in Utah are going to remember the shaking. So ideally, what that does, it makes them prepare a little bit and think this could happen in the future and it could be much worse.”

From a scientific standpoint, they learned that even a moderate quake on the Wasatch Fault will produce a long sequence of aftershocks.

“There’s been over 2,600 aftershocks,” he said, and they could go on several years. “Most of these that are happening are quite small. They are magnitude 1, maybe magnitude 2, so nobody is feeling them.”

From those aftershocks, they’ve discovered the Wasatch Fault is curved downward like the shape of a snow shovel, curving close to Magna.

“It’s a little bit closer to the surface than what we had previously thought,” the seismologist said. “So when we do get a magnitude 7 earthquake, we’re basically updating our models and the predicted amount of shaking from a future magnitude 7 earthquake is going to be a little bit larger than what we thought before.”

Seismologists still cannot predict earthquakes but the data they have gathered enables them to update their forecasts. Koper said there’s still about a 50% chance in the next 50 years that the Wasatch Front will experience a magnitude 6.5 or greater earthquake.

“It’s not perfect,” Koper said. “But, it’s much better than it used to be before having this data from Magna.”

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