Quake’s closeness contributed to stronger shaking

Friday’s 7.0 magnitude earthquake rocked Anchorage, jolting residents and damaging infrastructure. This was a big earthquake. But, for Alaska, the size wasn’t that unusual. What made it a big deal was the proximity to people and buildings.

Cracks in a ramp by Minnesota and International (Photo: Nathaniel Herz – Alaska Public Media, Anchorage)

Alaska is subject to a ton of earthquakes of varying sizes. And, state seismologist Michael West says quakes this size happen with some regularity.

“The vast majority of the time, those earthquakes are located some distance from the population centers,” West said.

But Friday, the earthquake was only about 7 miles from Anchorage. That’s why residents felt such a strong shake. West says the feeling is more rapid, and more vigorous, the closer the epicenter is.

“People who I’ve spoken to today, the word gunshot has come up many times. People felt like there was a sharp, burst if you will,” West said. “That’s something that will happen if you’re close to the earthquake. What you’re feeling is the ground itself. You’re feeling that fault line some distance away kind of crack and rupture.”

Now it’s time to assess the damage.

“We know where the earthquake happened,” West said. “What the rupture was like and the aftershocks. Really, what’s important in this is what’s happened to places that experienced such strong shaking.”

And that, he says, probably won’t happen right away.

“Past earthquakes suggest that it will take days before we know the true extent of the impact of this earthquake. That takes time to come out,” West said.

In breaking news situations like this one, it is easy for rumors and misinformation to spread. In this case, West wants to squash one particular rumor, about the occurrence of another, 8.4 magnitude quake. He says that’s just not true.

“Any time there is an earthquake of this size, there is very modest possibility of an earthquake of comparable or larger size…We have no evidence to suggest that that is in any way likely,” West said.

Aftershocks continued throughout the day Friday and into Saturday. And, West says they will likely continue long into the future. Though, they may not be felt.

“These aftershocks will continue, absolutely. They will lessen in their frequency. It won’t happen, that often. But some type of aftershock from this occasionally, or even a small magnitude, we’ll be recording years from now from this stuff, from this earthquake,” West said.

Anne Hillman contributed to this