I’m reading Simon Winchester‘s book, A Crack in the Edge of the World, which describes the 1906 earthquake in California and the events and geologic theories around it. (The book is most notable perhaps because of its unique dust jacket, which unfolds into a huge, 55cm X 93cm poster.)
The man isn’t half long-winded — I’m already almost a third of the way through the book and he hasn’t gotten past the plate tectonic theory and his reminiscences about his travel to other geologic hot spots. Title aside, this is less a book about the Great Earthquake of 1906 than it is about plate tectonics and the turn of the 20th century in general. Once you get past your expectations, it’s actually an interesting read,and it took me back to my high school geology classes, reminding me why I’d considered geology as a potential career path.
In North America, you tend to think of earthquakes as being a distinctly West Coast thing, occurring only in the westernmost parts of the US and Canada. After all, the eastern and western edges of the North American Plate are in the middle of the Atlantic Ocean and along the western coast of the continent respectively, thousands of miles from where we are. You forget (or never knew) that there are stress zones all over the place, crisscrossed with fault lines.
Ottawa itself is located in the Western Quebec Seismic Zone (a zone that includes Montreal and Cornwall) and is a part of the Ottawa-Bonnechere Graben, a 700 kilometer long rift valley that sits between two active fault lines, the Matawa and Petawawa faults.
The 1935 Timiskaming earthquake, a magnitude 6.2 quake, originated at the northwestern end of the graben, several hundred kilometers from Ottawa.
Apparently some form of seismic activity occurs in this zone approximately every 5 days. The last one (at the time I starting writing this on Friday) was on Tuesday at about 9:08 a.m, a 2.5 magnitude quake whose epicenter was about 180 kilometers northeast of us. Did you feel it? No, neither did I. (Granted, I was probably fast asleep at the time.)
I do remember standing in my living room in the early morning hours of March 14, 1996, though, getting ready to go to work when the wine glasses in the cabinet began clinking together. I could feel a rumbling in the floor under my feet and I thought a large truck must have been passing by. I was surprised to learn later that day that what I’d felt was a 4.4 earthquake that had originated in western Quebec. I’d only lived here for a year at that point and that was the first time I’d ever considered that eastern Canada could experience earthquakes — it’s certainly not something you ever really hear about in modern times in Nova Scotia. (As an aside, it was funny to see that the editors of the New York Times, in this PDF copy of a 1914 article about Nova Scotian communities being shaken by quakes, couldn’t manage to spell either community correctly. I suppose the fact that they warranted mention at all is a bonus.)
Natural Resources Canada‘s Earth Sciences Sector, which operates the Earthquakes Canada site, also operates the Community Internet Intensity Maps project. The CIIM seeks to compile and track information about area quakes from the people who are actually in the areas affected. To quote their info page:
By contributing your experience of the earthquake, either immediately afterward, or whenever it is possible for you to do so, you will have made a contribution to the scientific body of information about this earthquake. You will also ensure that your area has been represented in the compilation of the shaking map. […]
It is important that you fill out a questionnaire, even if your postal code is already colored-in on the Community Internet Intensity Map for the earthquake. The more questionnaires that are received for your postal code, the more reliable will be the average intensity assigned to that postal code. Even if you did not feel the earthquake, your questionnaire is important: in areas of lighter shaking, the “not-felt” responses are needed to prevent the average postal-code intensities from being too high.
So if you remember feeling — or not feeling — any of the quakes they’ve logged, including Tuesday’s, go ahead and stop by their site and submit your questionnaire. The more the merrier. (The USGS has a comparable system for reporting effects of 2.5+ magnitude earthquakes worldwide — they appear to currently not be effectively tracking earthquakes that originate in Canada, though, for technical reasons.)
Other interesting links:
- Earthquakes and geology in Canada:
- Natural Resources Canada, Earth Sciences Sector: Earthquakes Canada
- CBC News In-depth: Earthquakes in Canada: Surviving the moderate ones
- Public Safety Canada: Natural Hazards of Canada – Earthquakes
- BCIT Department of Civil Engineering: Earthquakes
- Geological Survey of Canada
- US Geological Survey Earthquake Hazards Program (worldwide information about and tracking of earthquakes). Includes a seismicity map of Canada from 1990-2000.