You're listening to Shortwave from NPR.

If you were in Seattle, Calgary, or Juno, you might have felt it.

October 28, 2012, a 7.8 magnitude earthquake struck off the coast of Canada near the archipelago

of Hydeuguay.

Earthquakes aren't unusual in that area because there's a big fault line nearby, but it turned

out.

Buried in the data associated with this earthquake was something unusual.

We were not particularly looking for something, but we were trying to look for earthquake

evolution processes.

When you and Finn is a professor at Florida State University.

I am a seismologist, or you can say a geophysicist in a more general term.

And so a couple years back, when he was looking at the data from the 2012 earthquake off

the coast of Canada, he noticed that before that big earthquake struck, there were records

of what looked like smaller earthquakes nearby.

Just migrating from north to south, and by noticing that, I thought I found a precursor

to the earthquake, and that was quite exciting to me.

And that would have been pretty cool on its own, a previously unknown precursor to a big

7.8 earthquake.

Just to make sure it was a real thing, when you and looked at some data from two years

before and the year after.

So not only 2012, but 2010, 2013.

And what we started to find is that such activities would happen every year.

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