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030310 seismic
Riddled with steep lines, a seismic monitor readout at Montana Tech shows the intensity of the earthquake in Chile. Photo by NICK GEVOCK/Montana Standard

BUTTE - Last weekend's magnitude 8.8 earthquake in Chile ranks among the most powerful ever recorded, and showed up prominently on seismic monitors in Montana, said Mike Stickney, director of earthquake studies for the Montana Bureau of Mines and Geology in Butte.

While hundreds of earthquakes around the world show up on the Montana measuring devices, this one stood out, he said.

"We've really only had a handful of events this big since the modern instruments were developed," he said in his office on the Montana Tech campus. "This is a scale of earthquake that only comes along once in a decade - it was huge."

Stickney noted that the decade has been exceptional, with the 9.2 magnitude quake in 2004 in Indonesia that produced a tsunami that killed more than 200,000 people.

He showed seismic charts from the monitoring equipment he studies every day while checking to see which quakes have shaken Montana. While the monitors pick up hundreds of minute earthquakes daily, Stickney said the quake in Chile was anything but small.

It showed.

The seismic graphs were riddled with steep lines, illustrating the intensity of the quake. And that occurred over a broad area that is inhabited by more than 2 million people, Stickney said.

"It's a huge region of the fault that ruptured," he said. "It would be the equivalent of from here to Salt Lake City and it all broke or ruptured within a minute or two."

Stickney said the type of fault along the west coast of South America, a subduction fault, is prone to producing more intense earthquakes. That's because one plate of the Earth is being forced under another fault, creating more fault surface to slip when the earth's plates suddenly move.

In comparison, a strike slip fault like that along the coast in California has less surface area and generally cannot produce as powerful of a quake. Stickney said such faults can produce quakes of up to 8.0 magnitude.

Chile has recorded the largest earthquake recorded in modern history, a 9.5 magnitude temblor in 1960, Stickney said. Saturday's quake, while not that powerful, dwarfed the 7.0 magnitude earthquake the devastated Haiti last month.

"This earthquake in terms of energy released was 500 times bigger than the Haiti quake," Stickney said.

Reporter Nick Gevock can be reached at nick.gevock@mtstandard.com.

 

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