Alaska is no stranger to earthquakes, and just over a month ago experienced a magnitude 7.0 quake which triggered a tsunami alert along the coast. The earthquakes which have shaken Alaska in 2019 have ranged from magnitude 2.5 to magnitude 5.9. The latest quake to shake the US state occurred Thursday, January 10 and measured a magnitude of 4.1.
Why is Alaska experiencing so many earthquakes?
According to Professor Bill McGuire, emeritus professor of earth sciences at University College London: “Alaska is one of the most tectonically active places on the planet.”
This is due to Alaska’s position above two moving plates, as Professor McGuire explains to express.co.uk: “It is on the Pacific Ring of Fire and many of the quakes – especially the big ones – result from the Pacific Plate plunging down beneath the North American Plate.”
“There are also plenty of other active smaller faults, so earthquakes in the state are a constant threat.”
There have also been changes in the environment which have contributed to Alaska’s increasing seismic activity.
Professor McGuire explained: “In Alaska, earthquake activity is increasing where ice loss due to climate change has been greatest.
“Some ice fields have lost a vertical kilometre of ice in the last 100 years, which has reduced the load on the crust beneath and made it easier for faults to move.”
When faults move, earthquakes occur – however predicting this is not something which can be done.
According to Professor McGuire: “It is simply not possible to predict earthquakes in the sense of saying a quake will happen on a particular fault on a particular date.”
Although, keeping track of certain faults that are known to move every so often can be a way to monitor quakes.
The earth sciences expert continued: “However, earthquakes on particular faults – or bits of faults – tend to happen with characteristic return periods that can vary from decades to centuries.
“So, if a fault normally ruptures to give an earthquake every fifty years or so, and there hasn’t been one for 70 years, then there is an elevated probability of one occurring and this probability can be calculated.”
Due to Alaska’s position on the explosive Ring of Fire, and it’s location making it one of the most tectonically active places on the planet, major quakes could “occur…at any time”.
One area of concern for scientists is “a quake in the so-called ‘Shumagin Gap’ where the Alaska Subduction Zone fault has not ruptured in living memory.”
Professor McGuire warns: “If this ruptures, the quake and resulting tsunami could be on a par with 1964 – or even worse.”
In March 1964 a huge magnitude 9.2 quake shook Alaska, triggering a tsunami and killing 139 people across three states.
This was the second largest earthquake ever to be recorded, the first being a magnitude 9.5 earthquake which rocked Chile in 1960.