The following map is by no means comprehensive as it takes time to locate such a large number of events, but several have been located, including all those of magnitude greater than 4.

Last month of earthquakes in the offshore region of Vancouver Island. Note that many earthquakes are still to be located and added to this map, as time permits.

Earthquake swarms happen in this region fairly regularly, although with no clear temporal pattern. While they are not a pre-cursor to a megathrust earthquake, they serve as a good reminder that this region is under constant tectonic stress and a large earthquake can occur at any moment, without warning.

Natural Resources Canada gathers information about how people experience earthquakes through “Felt Reports“. The perceived “intensity of shaking in relation to even a minor earthquake can indicate subtleties in subsurface conditions which influence the strength and duration of shaking of future, larger earthquakes. While similar information can be gleaned from seismic records, such data is relatively sparse in comparison to the density of earthquake reports received from people after an earthquake.

1. Why did you decide to become a Seismologist?
When I discovered there were courses on earthquakes at UVic, it was too interesting a topic to pass up. At the time I was working in space and atmospheric research, but wanted a change of career and I have never regretted entering the field of earthquake seismology. I am still in awe of the forces involved in tectonics and earthquakes.

2. How long have you worked with the GSC?
I did my Masters research project here in the 1990′s, but have been with the group as Earthquake Seismologist since 2000.

3. What do Seismologists actually do? Most people genuinely don’t know.
This can change from day to day, but most weeks see me spending at least two days locating earthquakes in western Canada (we located over 3000 in the region last year), plus I often give a presentation on earthquakes and their associated hazard. I respond to questions from the public, industry and other organizations, including news media and, finally, I try to get some research done from time to time.

4. You were a key figure in the recent ShakeOut BC campaign. Tell us more about the event?
This was a wonderful exercise, initially aimed at schools throughout BC, but when teachers, parents and, eventually, businesses and other organizations found out about it, it turned into a BC-wide event, with more than 10% of the population joining the drill. We chose the date of 26 January (the anniversary of the last Cascadia megathrust earthquake which occurred in 1700) and encouraged people to participate in the drill at 10am. To think that more than 470,000 people did a “duck, cover and hold on” at that time is wonderful. We simply need to build on that number in the coming years, so this action becomes second nature to everyone, especially as people don’t always think clearly in extreme situations. And, yes, I was under my desk for the drill.

5. Earthquakes happen all the time. Why do you think people do so little to prepare?
People in BC have generally become complacent because it has been so long since we have experienced a large, damaging earthquake. It is one thing for me to tell people of the risk and for them to witness earthquakes elsewhere in the world, but quite another to have that driven home with a local event. I simply hope people “shake off” their complacency and get prepared before we do have a large event – this is the impetus behind my active outreach work.

6. Can you give us an expert’s view on the recent earthquake in Christchurch? Why did this particular earthquake cause so much damage?
This earthquake was smaller than that which occurred last September, but it was located directly under the city and at a very shallow depth (the deeper an earthquake, the more the seismic waves are weakened before they reach the surface). The ground shaking was very strong and larger than most buildings were designed for – this is because this fault was unknown until the magnitude 7 earthquake last September. We are certainly looking closely at this earthquake, especially for the city of Victoria as there are many similarities in construction history between the two.

6. Can you give us an expert’s view on the recent earthquake in Japan? Why did this particular earthquake cause so much damage?
There was actually little building damage from the earthquake itself because Japan has been so very proactive in developing earthquake resistant design and construction, particularly after the Kobe earthquake in 1995. What caused the dramatic damage was the tsunami. They simply had not anticipated such a large megathrust so had under-estimated the maximum tsunami height. This is another earthquake from which we are trying to learn as many lessons as possible, to help prepare for the inevitable Cascadia megathrust earthquake along our coast.

7. How likely is an earthquake to happen on the West Coast of North America?
This is a very tectonically, and therefore seismically active region. The coast has seen many large earthquakes in the past and they will certainly happen again in the future.

8. Do all those small earthquakes occurring each year reduce the chance of having a larger earthquake?
Unfortunately, the amount of stress released in the routine, low-level earthquake activity is negligible compared to that which is built up and bound to release in large events.

By Peggy Hamilton