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Research cruise decodes links to the past

September 6, 2011
Amy Dove
Dr. Randy Enkin of the Geological Survey of Canada uses a hair dryer on a freeze core of sediments.

When Audrey Dallimore pulled a sediment core out of Barkley Sound this summer she couldn't help but notice 50 years of history were missing.

The Royal Roads University researcher and professor has collected and analyzed sediment cores off the B.C. coastline for a decade in an attempt to track climate patterns and the historical frequency of earthquakes. This latest finding may have swept 50 years worth of data off the ocean floor, but it gave her invaluable insight into the how much a tsunami that originated an ocean away in Japan last March can affect this coast.

"Now we know what tsunami disturbance on our coastline looks like," Dallimore says, noting that can unlock the answers to other disturbances visible throughout history. "We are able to refine what we think is the frequency and magnitude of earthquakes along this coast."

Dallimore acted as chief scientist on a research cruise Aug. 13-21 aboard the Canadian Coast Guard Vessel Vector. The trip was her first chance to test out new equipment and the results were favourable. The addition of a Geotek Multi-Sensor Core Logger (MSCL) to her research arsenal means that the sediment cores she pulls information from can be analyzed at international geologic standards.  To be shared with other researchers, the MSCL is the only one of its kind on the West Coast. It was funded by grants through Royal Roads from the Canada Foundation for Innovation and the BC Knowledge Development Fund.

Within the funding grant, Dallimore also received money to develop two new freeze coring apparatuses. The devices are filled with dry ice, which sediment then binds to creating the core. The coring apparatuses are left in the water for approximately 30 minutes before a piece of history is pulled back onto the boat. The result is an "inside out" core where sediment lines can be decoded to show water properties, mineral levels and other readings that paint a picture of what was happening in the environment thousands of years ago.

Helping secure that funding is what Deborah Zornes, manager of research development, and her team in the Royal Roads University Office of Research do best. Zornes was invited on the research cruise so that she could see the dollars in action and get a better idea of the projects her department works to support. That insight will help Royal Roads prepare better grant applications in the future.

It was the trip of a lifetime and she was put to work, Zornes says. From drilling holes to secure equipment on board, to compiling data for sub bottom profiling, Zornes joined the team in work days that spanned from 6 a.m. to 10 p.m. before the night shift started.  By Day 2 she was logging the majority of data streaming into the onboard lab.

"It was thousands of pieces of data by the time we were done," she says. "There was a lot of double checking, double checking again and checking again because if the data is not right it's worthless."

Her work on board gave the scientific team more time to focus on collecting the information. That help, combined with the new equipment saw the cruise bring in more samples than ever before. On previous research cruises they would spend three to four hours on one core, whereas this time they processed one core an hour. In one day along the team captured and processed six cores with the multi-sensor logger.

"This was a huge increase in what we were able to do on one cruise," Dallimore says.

The sophistication level in which they processed the core has also soared. Previously, Dallimore and the team would bring a core up onto the deck of the ship, photograph it and then cut the three-metre core into three pieces so it would fit in the ship's freezer. They wouldn't be able to analyze it further until they reached dry land.

"We were able to analyze the core right on board now," she says. "To our knowledge it's a very unique technique we have developed. We are not all that sure what we are going to see."

With the team back at the lab, the next six months will be dedicated to analyzing the data, and comparing it to scans of the same cores taken about a month after the cruise. They will date the cores, and attempt to connect sediment layers to climate data and other factors.

"We can come up with a story about the environmental history that will explain the core," she says.

Evidence of two of B.C.'s largest coast line earthquakes were found in every core they sampled, Dallimore says. There are clear sediment disruptions marking the magnitude 9 Cascadia mega thrust earthquake on Jan. 26, 1700 and the magnitude 7.3 earthquake centered under Forbidden Plateau in central Vancouver Island June 23, 1946. The later is Canada's largest onshore earthquake to date.

The cores also provide evidence of how disruptive shallow crustal quakes can be even though most people equate "the big one" with a subduction earthquake. This information is invaluable to city planners as it allows them to better identify the risks of tsunamis and earthquakes in different areas, as well as the potential impacts of that and plan accordingly, Dallimore says.

The intent is for this research to help communities to be better prepared in the event of an earthquake by strengthening building codes and informing policy, she says. The earthquake in Japan really raised awareness of the realities a developed country has to face after a major natural disaster in terms of infrastructure and human needs.

"It's very timely, this work we are doing," she says. "Science isn't done until you have shared it. That means sharing it in ways that are useful to communities."