ANCHORAGE, Alaska (KTUU) – The Alaska Earthquake Center is addressing questions about the magnitude 6.0 earthquake that shook Southcentral and Interior Alaska on Thanksgiving morning.
The Alaska Earthquake Center is calling it the Susitna Earthquake.
Though the epicenter of the quake was close to the epicenter of the M7.1 earthquake on Nov. 30, 2018, the Alaska Earthquake Center said it was not an aftershock.
“Aftershocks are kind of a man-made, artificial sort of designation for earthquakes. There’s nothing in the earth that says this is an aftershock versus not an aftershock,” Austin Holland, Alaska Earthquake Center director of operations, said.
“It was outside of the rupture area of the 2018 Anchorage earthquake, which is generally what we use to identify whether an earthquake is considered an aftershock or not,” he said.
Alaska Earthquake Center compares Susitna Earthquake to 2018 Anchorage Earthquake(Sarah Noel/Alaska Earthquake Center)
The Susitna Earthquake also happened just days before the seven-year mark since the 2018 quake, leaving some asking whether it was a coincidence.
Holland said that’s what it was.
“This is an active area with a large number of earthquakes throughout our recording history,” he said. “I know it seems really odd that there is such a good coincidence between the timing of these, both kind of around the end of Thanksgiving, end of November kind of timeframe, but there is no seasonality to deep earthquakes like this.”
Alaska Earthquake Center looks at Susitna Earthquake(Cade Quigley/Alaska Earthquake Center)
Another interesting thing about the quake is that some people farther from quake felt the shaking stronger and longer.
“Because this was deep enough, it was almost as deep as it was as far as it was from Anchorage, creating this ability to have energy more broadly spread over a broader area and being felt broadly, including all the way north to Fairbanks,” he said.
Alaska Earthquake Center looks at Susitna Earthquake(Michael West/Alaska Earthquake Center)
The Cook Inlet Basin also played a role in some areas, including Nikiski, which felt the quake longer and stronger because of the way the sediments impact the velocity of the seismic waves.
“In addition, sometimes basins, depending on the orientation of the waves entering the basin, the waves can be trapped in the basin and reverberate. And so all these factors can play together to change people’s experiences. In general, people’s experiences can vary dramatically even within the same basin,” he said.
Some also received a notification around the time the quake started. It’s a part of an addition to the Android system that was put in place about a year ago.
“It hasn’t happened that we’ve gotten a whole lot of notifications in Alaska from the Android system, partly because a lot of our earthquakes are offshore in the Aleutians, and you need people’s Android phones to then create those shaking alerts,” Holland said.
“One of the things we’re looking to at the Alaska Earthquake Center is producing a system that isn’t reliant on where people’s phones are, but is reliant on where we put instrumentation throughout the region. And this is called Earthquake Early Warning,” he said. “The goal is to really provide people a few seconds to tens of seconds to prepare before the strongest shaking reaches where they’re at.”
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