A UCalgary earth scientist is part of a research voyage to study the huge Queen Charlotte-Fairweather Fault system, in an effort to improve earthquake prediction capabilities.
University of Calgary earth scientist Rachel Lauer is on a ship off Canada’s West Coast, investigating a huge geological fault where a massive earthquake is expected one day.
Lauer, assistant professor in the Department of Geoscience in the Faculty of Science, is aboard the John P. Tully, an oceanographic science vessel in the Canadian Coast Guard, based in Sidney, B.C. She is one of 15 scientists — nine from Canada and six from the U.S. — participating in a three-week research cruise.
“The purpose of this investigation is to collect data that will provide information on the recurrence intervals between major earthquakes,” Lauer said in an email interview from the ship.
The researchers are studying submarine features, including canyons, gullies and volcanic cones, in the Queen Charlotte-Fairweather Fault system, which extends from west of Vancouver Island to Alaska. Their work should shed light on the distance the fault has moved in the past. They are also extracting, examining and dating cores from the ocean floor sediments, to investigate abrupt movements of the fault associated with past earthquakes.
Scientists are still a long way from accurately predicting earthquakes, Lauer said. “But by piecing together the history and current conditions of the fault, we get closer to understanding the timing and potential hazards associated with future events.”
Four large quakes generated in last 100 years
The 900-kilometre Queen Charlotte Fault is a seismically active boundary between the North America continental plate and the Pacific oceanic plate.
Lauer said the movement between these two enormous plates is about as fast as a fingernail grows. But that’s enough to exert tremendous force along the fault, which periodically breaks and generates earthquakes, potentially stimulating sub-marine landslides that can form tsunamis.
Four large earthquakes have occurred along the Queen Charlotte Fault within the last 100 years, including a magnitude 7.8 quake just a few years ago in 2012. In 1949, the fault generated an earthquake of magnitude 8.1 — Canada’s largest recorded quake since 1700. It was larger than the 1906 San Francisco earthquake that destroyed more than 80 per cent of the city.
Previous research expeditions conducted by the U.S. Geological Survey have mapped the Queen Charlotte Fault and surrounding seafloor and also the subsurface, using seismic methods.
During this cruise, scientists are using piston coring equipment lowered by crane over the side of the ship. It can recover up to six metres of continuous cores from the seafloor. The recovered cores contain small plankton that die and settle to the seafloor, along with sediment washed off the continent via rivers and streams and transported by glaciers. This represents a record of sediment deposited and fault movement over approximately the past 10,000 years.
Past earthquakes and associated ground shaking typically show up in the core samples as coarse deposits called “turbidites.”
“The timing and distribution of these deposits in the sediment record can be helpful” in determining the timing of and interval between past seismic events, Lauer said.
Focused on studying fault’s gases and fluids
Previous research hasn’t investigated the hydrogeology, or subsurface flow, of the Queen Charlotte Fault. Little is known about potential pathways of gases and fluids venting from active fluid seeps and mud volcanoes in the fault zone. Lauer’s research is focused on trying to answer questions such as where the fluids and gases are coming from; whether they can reduce friction along the fault or even "cement" the fault zone; and whether the gases contribute to the greenhouse effect in global warming.
Her typical day, after a 6 a.m. breakfast, consists of sampling the pore water from each core and preparing samples for geochemical analysis — done back on land — to determine the fluid source process and region, flow rates, and the total flux of nutrients and gas from the sub-seafloor. Gas and fluids seeping out on the seafloor produce “hard grounds” from calcium carbonate cementation of the seafloor. This provides hard, rocky bottom habitat for fish, deep-sea corals and sponges that are critical to Alaska’s fisheries.
“Discovery and investigation of these sites is also being undertaken to expand our knowledge of how these hard ground ‘oases’ within a sediment desert are being utilized by fish,” Lauer said.
Lauer has sailed on six previous expeditions during her PhD and postdoctoral work. As for her current cruise, she emailed: “This is such a great group of scientists from the U.S. and Canada,” including those from Natural Resources Canada, the Geological Survey of Canada, and the U.S. Geological Survey.
Lauer is posting tweets and photos of the research expedition at her Twitter account.
As part of its strategic direction for 2017-2022, the Faculty of Science is directing its research efforts toward four Grand Challenges. The Grand Challenges harness current strengths, look to future opportunities, and allow the faculty’s researchers to explore new discoveries. Research under the Grand Challenge Understanding Earth’s Evolving Systems includes Earth as a system from the core to the magnetosphere, biodiversity and conservation, and the intersection of the natural and built worlds.