Alaska’s recent 7.0 magnitude earthquake has had lasting impressions on the city of Anchorage, where aftershocks are still shaking the area. The remote US state is subject to earthquake activity regularly, but magnitudes often rest in the 2.0-4.0 zone, unable to cause much damage. In the past, there have been serious earthquakes in the region, which have been severe enough to level settlements and kill hundreds. One particular earthquake in 1964 hit with a force of 9.2 magnitude in the Prince William Sound region, triggering tsunamis and hailed as the most powerful earthquake in US history.
The November 30 earthquake struck with a force of 7.0 magnitude near the city of Anchorage, at 5.29 pm.
Taking place at a depth of 24 miles, the earthquake was strong enough to heavily shake the surface, producing cracks in the roads above.
Two main effects of the heavy shaking were landslides and liquefaction, when solid ground starts to behave like a liquid and swallows objects.
The United States Geological Survey (USGS) said a total of 6 miles squared were under the effects of landslides, and roughly 70 people were under threat.
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Liquefaction was a much larger concern however, as 136 miles squared of land and 3,500 people are thought to have felt the effects.
USGS mentions earthquakes of this magnitude are relatively frequent, with a total of 14 others rocking the 150km area around yesterday’s site being over magnitude 6.
USGS says: “Two of these – a magnitude 6.6 earthquake in July 1983 and a magnitude 6.4 in September 1983 – were at a similarly shallow depth and caused damage in the region of Valdez.”
The tremors were spearheaded by the the Pacific tectonic plate moving northwest in relation to the North American plate.
This mechanism taking place causes the near constant rumblings in the state, as the plate moves a total of 57 millimetres per year, subducting Alaska.
Subduction is when one plate moves under another, dragged down by gravity, which can cause tremors.
When two different plates rub together, the crust can get stuck in places, building up energy.
This energy can then be released at any given moment, which comes in the form of an earthquake.
Is there a tsunami warning?
With subduction, both ocean crusts and continental crusts can rub against one another, which can cause tsunamis.
This has happened before in Alaska, when the great earthquake of 1964 ushered in a tsunami to the state.
For yesterday’s earthquake, there were initially concerns the tremors could cause a tsunami.
However as of December 1, there are no tsunami warnings for Alaska.