The truth about earthquakes, stability of the Canadian shield and some common sense.
So, on January 25, 2013 an earthquake rattled the northern shore of Lake Superior. With a magnitude of 2.3 and an epicenter located approximately halfway between Terrace Bay and Nipigon Ontario. I myself felt it from inside my home located in Nipigon.
By rattled, I sort of mean noticed (barely). At 2.3 magnitude it was barely above the “felt it” detection. I didn’t realize it was an earthquake at the time however i did find it odd – my initial though was a dump truck driving by as that is realistically what it felt like. Of course I didn’t see a dump truck and it only lasted for a second or two so I figured it was something else.
In all fairness, I am a geologist, and made note mentally of the odd occurrence. I have a strong suspicion that very few if anyone locally actually realized what it was until the news from the earthquake center started coming out.
So what is a 2.3 earthquake?
Well, a dump truck driving by was about right for me, energy wise a 2.5 earthquake is about equivalent to a moderate lightning bolt hitting the earth. The trains that barrel through towns around here have an equivalent of a magnitude 4 earthquake to those around the tracks (cracks in my plaster seems to support this 🙂 ).
So does this mean that the Canadian shield is prone to earthquakes?Â
Sure, but not for the reasons you think. A little over ten thousand years ago (exact date eludes me) the entire area was covered by up to 3km of ice during the last glaciation period. The shear weight of that ice actually pushed the crust of the earth down into the creamy liquid mantle throwing the buoyancy of the crust. Then over a relatively short period (in geological time), that weight was removed as the ice melted. Since everything in the universe desires equilibrium, the crust rebounded – albeit very slowly. Think of pushing a board under water, let go and it springs back up. This process is still ongoing at a rate around 1 foot per century (0.3 cm per year).
So do they get any bigger?
In a word no, not in a single lifetime. The earthquakes around these parts are tiny as the crust rebounds, as time goes on their power gets less as the crust approaches and reaches equilibrium. The risk for the north shore of Lake Superior (as calculated by USGS) is a .02% chance of a magnitude 5 earthquake in the next 10000 years, with a 0% chance of an 8.0 earthquake in that same time period. So basically if you felt it, you are lucky and in the minority and it will likely never happen again to you.
And they want to store nuclear waste here.
Have read and a heard a few things along the lines of disbelief that they want to store nuclear waste in the region – and that now that there’s been an earthquake they should discount the area. Well, small earthquakes are well known by scientists around these parts, they know why, where, probabilities and the risks. So they have already designed everything with earthquakes in mind. The containers and storage compartments are likely built to survive the strongest earthquake ever (yes that can be done). Buildings in Chile are build to survive a magnitude 8 or 9 (been a few years). And those are buildings’, not basically holes in the ground where such building methods would be even stronger.
If we have a 8 or 9 magnitude earthquake here, there will be other major issues to be concerned about other than nuclear waste – it would likely mean we had been impacted by an extinction level asteroid or comet. But rest assured, the nuclear waste would likely survive better than us.
