(Edmonton) Physics experiments are often thought to take place in closed labs, but geophysicist Jeff Gu created Alberta's first broadband seismic array by embedding seismometers in communities across the province.
"The majority of the stations are on private land, thanks to the great support from the community," Gu says. "For this reason, we are truly grateful for the understanding and support of landowners who host the stations. They are the unsung heroes behind this project."
Gu, who also goes by Yu Gu, started CRANE (the Canadian Rockies and Alberta Network) in 2006, two years after he became a faculty member in the University of Alberta's Department of Physics. His goal was to use broadband seismic recording equipment to understand the nature of the geological mantle and crust below Alberta's surface.
Each station costs about $35,000 to make. They are built by Gu and his team and consists of a battery-powered seismometer that is buried underground. The batteries are recharged by solar panels mounted on modest "towers" that are also built by the research team.
Besides hosting the equipment, landowners have been active in promoting awareness of CRANE and its scientific goals.
"Helping to foster healthy discussions of broadband seismology is really one of the long-term objectives of this project," says Gu. "In many instances the host families do communicate with their friends and community about the nature and outcomes of the stations they host. We leave that decision at the discretion of the landowner as long as the interaction does not lead to unwanted attention or security issues."
One of the questions the project set out to answer was whether any old geological faults have been affected by industrial activity, such as steam-injection petroleum extraction.
"We have our suspicions in multiple areas in which small earthquakes (often termed 'microseisms') have taken place repeatedly, but I will not be more specific at this stage until the results are more conclusive and/or published," he says. "Together with Virginia Stern from the Alberta Geological Survey and Ryan Schultz (a graduating MSc student from my group who recently assumed a position at the Survey), we have gotten many interesting, potentially important, results on the microseismicity in central and southern Alberta based on the data from the array."
CRANE has also produced an "overwhelming" wealth of information about the Earth's crust and mantle.
"In addition to mapping the microseimicity (which is near completion based on CRANE data during the past four or five years), we have completed, or are in the process of completing, regional surveys of depth, seismic velocity and anisotropy of the crust," Gu says. Anisotropy is the concept that waves travel at different speeds in different directions. The Earth's crust can contain anisotropic sections due to faulting or layering.
Gu summarizes: "The Alberta crust is quite complex with large variations in seismic wave speeds and crustal thickness. Encouraging results have also been obtained for mantle velocity, layering and anisotropic structures. "
Gu says some results have been published over the past two years, but several papers based on CRANE data are expected to appear in geophysical journals in the coming months.
"This is actually the most fruitful time for everyone involved in this project after years of hard work," says Gu, who adds special thanks to his past and present students for their work on CRANE. "We are quite excited about the richness of the information from the array and the research aspect is only going to get better in the coming years."
CRANE was established with primary funding from the Canadian Foundation for Innovation, a New Faculty award from Alberta Innovates, a University of Alberta Start-up Fund and ARC Resources Ltd. For the past three years, the field-related operations have been partially subsidized by the Alberta Geological Survey.