We have the good fortune of living in a beautful corner of the planet where spectacular coast mountain scenery borders the temperate Pacific Ocean. But this priviledge comes at a price. The same forces that lift the coast mountains from the sea are responsible for one of the most powerful of natural disasters: earthquakes. In this talk, I will discuss several distinct classes of earthquake that occur in the Pacific Northwest and the seismic hazard they pose. This list includes the highly anticipated magnitude 9 "megathrust" event that will rupture the entire Cascadia plate boundary from offshore northern Vancouver Island to northern California. It also includes less predictable "crustal" earthquakes up to magnitude 7.5 that can occur on faults anywhere in the region, and deep "intraslab" earthquakes up to magnitude 7 directly beneath major population centers such as Seattle, Victoria and Vancouver. "Slow earthquakes" with magnitudes of up to 6.5 represent a recently discovered class of tremor that goes essentially unnoticed by the general public but which occurs at regular ~14 month intervals below Vancouver Island. Although earth motion during slow earthquakes is too protracted to generate significant seismic waves, these events may serve as harbingers for the next megathrust event as they transfer stress along the Cascadia plate boundary.
Michael Bostock is Professor of Seismology in the Department of Earth, Ocean and Atmospheric Sciences at the University of British Columbia. His research focusses on the structure and seismicity of subduction zones, both active and ancient, with particular focus on Cascadia and the Pacific Northwest.
Please RSVP by end of day June 5th, 2017 to firstname.lastname@example.org or preferably, EventBrite.
ARPICO will be holding its 2017 Annual General Meeting before the Event, from 6:00pm until 7:00pm. All are invited to attend.
June 06, 2017 at 6:00pm
Roundhouse Community Centre - Room B - (181 Roundhouse Mews, Vancouver, B.C.)
June 12, 2017
Last Tuesday June 6 was a hallmark summer Vancouver evening: sunset light filling the air with a warm hue, gentle breeze brushing over False Creek, people out for walks and bike rides. Faced with the choice of spending such a lovely weekday night enjoying a drink and a chat in some patio with friends or indoors listening to a scientific lecture on earthquakes, I'm willing to wager that most people would go straight for the former. Yet, upwards of 50 people graced ARPICO with their attendance at its second public event of the season "Earthquake Zoo in our Backyard: the Crossroads of Faults in the Pacific Northwest" delivered by Professor Michael Bostock of UBC at the RoundHouse Community centre. And I venture to say that all went home satisfied to have acquired a much better picture of what goes on under the very ground we stand on every day.
In spite of the amount of attention the topic of earthquakes receives in our city, the lower mainland, Vancouver Island, and the Pacific Nortwest in general, I'm sure that the majority of us who attended took away much new information about the local crustal dynamics, which we completely ignored before. For one thing, while the so-called Big One is on everybody's mind when things seismic are concerned, we learned that there are 3 other types of earthquakes that can hit our area, some of which shallow enough that they'd cause major damange even though they would "only" top out at approximately magnitude 7. And speaking of the Big One, its estimated frequency is about once every 590 years, with a couple of hundred year uncertainty on either side of that number. Now, your next question might be how long ago the last Big One was... about 500 years as we heard it from our expert speaker.
I venture to say that all went home with enriched, if discomforting, knowledge of our shaky underground, but not before hanging around for another hour after the end of the talk, chatting informally with the speaker himself and amongst each other while enjoying a little food and some super desserts.
Once again we were fortunate to have the Consul General of Italy, Massimiliano Iacchini, offer the audience an informative introduction to the evening. We are delighted that the Consulate of Italy is firmly behind this sort of activity.
Lastly, of course a huge GRAZIE to all who kindly made time to attend and liven up the evening with their numerous questions and comments. I hope the enthusiastic response and participation I witnessed last week will continue through our summer and fall activity. Stay tuned through our website, arpico.ca, for information on what's coming.