Seismology Research (Chief Scientist Vlog)

Natural Resources Canada’s Chief Scientist Donna Kirkwood talks to seismologist John Cassidy and student Jeremy Gosselin about earthquakes-related research.

Transcript

Donna:

How about we start off by chatting a bit about what seismology is all about?

John:

“Seismo” is a Greek word meaning earthquakes, and so seismology is the study of earthquakes. And it’s the study of wave propagation through the earth.

Donna:

Can you talk a bit about some of these seismic events or earthquakes that occur in Canada?

John:

Of the 5000 earthquakes each that we record each year, and locate, about just under 100 are felt. And so once an earthquake is felt then people want to know: What has happened, what can I expect? Could we expect a tsunami or damage from this earthquake? So we do provide information very quickly after any of these felt earthquakes – or significant earthquakes, because of course because the data from our monitoring network comes in both to Ottawa and to here to Sidney (BC) in real time.

Donna:

What would you say are your proudest moments or your greatest achievements?

John:

One of the greatest achievements, and it’s had a global impact, is understanding subduction zones in earthquakes, which is where the worlds largest earthquakes occur. So subductions zones are where the ocean plate is being pushed beneath the continent, like it is right here in Sidney. This is where the magnitude 9 earthquakes occur around the world. So Japan, Alaska, Chile, Mexico and here in Southwestern British Columbia.

So when I was a grad student 30 years ago, we didn’t realize that subduction zone earthquakes – the big magnitude 9s – occurred off of our coast. And over the course of 25 years of research that included people around the world, in fact, different types of data, we now know that those magnitude 9 earthquakes do occur just off of our coast. We know how big they can be, we know how often they occur. We can map out today what the energy is being stored for the next one. We can generate models of the shaking we can expect and the shaking we can expect and the tsunami we can expect. So all of this research has now been folded into our building codes, our bridge codes and is being used by emergency managers.

Personally, what I’m proudest of, has been my students. They are doing terrific science around the world and all across Canada, including the work that Jeremy Gosselin has been doing both here and out west for his PhD program at the University of Ottawa. I’m incredibly proud of my grad students over the years.

Donna:

Okay, thanks a lot. And I think we’ll be highlighting the work that Jeremy has been doing with Natural Resources Canada. So stick around and look out for Jeremy’s work on Simply Science. Thanks John.

Jeremy:

Hi, I’m Jeremy Gosselin. I’m a PhD student at the University of Ottawa studying seismology. I’m a former graduate student of John Cassidy at Natural Resources Canada and I’m standing here in the Advanced Research Complex at the University of Ottawa where a lot of cutting-edge research is being done in fields like photonics and earth sciences.

I’d like to talk about why it’s important for us to estimate soil conditions when we’re considering seismic hazards. To help illustrate my point, I put together a short computer simulation that I’d like to show you.

Imagine two structures located near an earthquake. The first structure is built on bedrock and the second structure is built on soil. As seismic waves that are released from the earthquake encounter soil, they’ll actually slow down and amplify. Those seismic waves will also begin to bounce around within the soil layer and resonate. What happens is that the structure that is built on soil will actually experience a much longer duration and a much more severe level of shaking during an earthquake, compared the structure that was built on bedrock, all other factors being equal.

If engineers know what the soil conditions are at a particular site, they can anticipate the level and severity of this seismic amplification and resonance and they can incorporate that information into safe building practices and safe building design for a particular site condition.

My research with John Cassidy and Natural Resources Canada focussed on developing new methods to estimate soil conditions using recordings of ambient or background seismic noise. These methods are really nice because they’re non-invasive, non-disruptive and relatively inexpensive to implement.

We used these methods to estimate the soil conditions at several locations within the town of Kitimat, British Columbia. This is a region that’s experiencing a large number of major infrastructure development proposals. Our new methods are useful for engineers or geoscientists who are interested in quantifying or estimating soil conditions in different regions. And our findings on the soil conditions in Kitimat are useful for engineers or municipal officials, so they can take that information and incorporate that into safe building practices.

I’ve had a great experience working with Natural Resources Canada and I hope to continue to conduct research with them in the future.

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