Unlocking paleoseismic and ecocultural history on the West Coast

February 21, 2018
Assoc. Prof. Audrey Dallimore

When will the “big one” hit?

That’s the question marine geologist Audrey Dallimore is often asked.

An associate professor in Royal Roads’ School of Environment and Sustainability, Dallimore studies the marine sediment record of offshore and coastal earthquakes and tsunamis, topics increasingly at top of mind for people living on the West Coast.

She and her colleagues in Canada and the U.S. are joining forces to provide information about the frequency of destructive earthquakes and which areas could be most impacted by tsunamis.

Although their research doesn’t focus on prediction, it supports preparation and understanding areas of sensitivity along the coastline, Dallimore says. “This information will be very valuable for coastal communities and governments to help us prepare for the next ‘big one’.”

Their work will unlock the 10,000-year geologic record of the entire Cascadia subduction zone (CSZ), a 1,000 km-long fault that runs from northern Vancouver Island to northern California. The CSZ is a megathrust fault capable of the most powerful, destructive earthquakes.

The research brings together findings from the B.C. coast where glaciers carved deep fjords and from the expansive, non-glaciated beaches and marshes of the U.S. West Coast. Together, those records comprise a huge set of oceanographic and marine sediment data that can answer questions about the entire CSZ region.

“We’ve been working for a number of years to bring records from the U.S. and Canada together, because it is the functioning of the entire subduction zone in geologic time that will give us clues about which areas of the North American coastline are mostly impacted, and answer questions about whether the entire subduction zone ruptures at one time, or if one end or the other is more active,” Dallimore says.

The results of the Canadian study will be available in 2018, and will complement a seminal study of the seismic record of the American portion of the CSZ conducted by scientists at the University of Oregon along with Dallimore and others, which was awarded the Geological Society of America’s 2016 Kirk Bryan Award for Research Excellence.

Over the last ten years, Dallimore and her colleagues procured marine sediment cores during cruises on the Canadian inshore research vessel CCGS Vector. The research was funded by the Natural Sciences and Engineering Research Council of Canada (NSERC) and through collaboration between Royal Roads University and the Geological Survey of Canada Pacific (GSC).

The RRU-GSC partnership also facilitated acquisition of state-of-the-art equipment for a shared core logging lab located at the Institute of Ocean Sciences in Sidney, B.C. That equipment is used to read the “fingerprints” of past earthquakes in the pattern of annual sedimentation revealed in cores obtained in fjords along the B.C. coast.

“Certain areas preserve a sediment record that is in annual layers, year by year,” says Dallimore. “As one young First Nations boy remarked, ‘You’re telling me it’s like tree rings that show how a tree has been growing?’ And that is exactly what they are.”

Dallimore’s coastal research has been aided by Royal Roads’ 24-foot research vessel Raincoast Survey, acquired in 2013 with support from the Canada Foundation for Innovation and the B.C. Knowledge Development Fund. Equipped with a high-resolution multi-beam system used to map the seafloor near the shore, the Raincoast Survey has also facilitated graduate student research and community place-based learning in the Salish Sea, where scientific records complement traditional ecological knowledge of ancient Indigenous clam garden sites.

Prof. Leslie King (left) & Assoc. Prof. Audrey Dallimore during field research

Working with the NSERC PromoScience program, archaeologists from other post-secondary institutions, Gulf Islands National Park Reserve, the WSÁNEĆ and the Hul’qumi’num Treaty Group, Dallimore and Royal Roads Prof. Leslie King established a program of community outreach and study of the ecological, geomorphological and cultural impacts of traditional clam gardens in a unique combination of modern science and traditional ecological knowledge.

“The gardens established by First Nations are the result of incredibly detailed ecocultural knowledge of all parts of the environment. As scientists, we come in and study one or two things as aspects of the environment for a couple of years. But our work with Indigenous communities opens our eyes to the larger ecocultural landscape of uses of the fish, the trees and the land. And all of that is wrapped up within a human culture,” Dallimore says.

“The counterpoint is where we are today, relating with Indigenous communities and trying to bring forward their deep knowledge of and deep experiences of colonialism. How do we assimilate that learning when we speak about our knowledge of earth history and weather history and climate and ocean history? It’s very rich and it’s very new.”

This profile was developed with the assistance of the Research Support Fund and will be included in the forthcoming 2018 Research in Action publication featuring Royal Roads University faculty and student research.