Many people report hearing the big 7.0 earthquake on Nov. 30 before feeling it. Many also say the same thing for aftershocks.

"Like a big truck going by; that's what you think. As soon as it hits you think, 'Dang, that's somebody driving way too fast down the street.' And then all of a sudden you don't see a truck and then all of a sudden everything is shaking," said Anchorage resident Crystal Bitner.

State Seismologist Michael West, with the Alaska Earthquake Information Center, says it has to do with certain seismic waves that are emitted from an earthquake; P and S waves. West says P waves travel faster than S waves and the audible frequency of a P wave can end up in the range where people can hear them.

"They may not be strong enough for you to feel them but they are strong enough to vibrate the air and create the sound that you hear," West said.

He says the S waves are stronger than the P waves and someone may feel a shake when the S wave reaches a person. He says the time from when a person may hear a quake to when they feel it could be several seconds depending on how far away that person is to a quake.

But West points out that this process doesn't always happen and says seismologists measure an earthquake's vibrations as they happen, as opposed to sounds from the air.

Asked whether people could use the sound as an early warning system to take cover, West didn't disagree.

"It's not a crazy idea at all and I wouldn't tell somebody not to use the sound," he said.

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