New Seismic Research in Ground Motion Potential Assessment for Fort St. John and Dawson Creek Area

Vancouver, BC – February 22, 2022 – Geoscience BC has published the results of a project that assessed the potential amplification of ground motion associated with earthquakes generated by hydraulic fracturing and fluid injection in an area around Fort St. John and Dawson Creek in British Columbia’s Northeast Region. These results add detail to findings for a larger area completed earlier in 2019.

The project addresses public concerns relating to seismicity and oil and gas industry activity in northeastern BC, especially in areas close to communities and infrastructure. It examined how seismic waves from earthquakes can potentially be amplified in specific shallow geological conditions.

Lead researcher Dr. Patrick Monahan said at the project outset: “Most recent studies in this area have focussed on the reduction of ground motion as you get further from the seismic event. But seismic ground motions can also be amplified significantly on sites underlain by certain sediments, compared to sites on bedrock or firm ground.”

Now complete, the information generated by the project is being made publicly available. The results will be particularly useful for regulators and industry operators managing energy industry activity to identify areas which may have an increased likelihood of felt events due to local surface conditions.

The researchers collected data from over 4,800 petroleum industry wells, water wells, and geotechnical boreholes. The data was used to prepare a new depth to bedrock contour map at a 1:100,000 scale. High resolution digital topographic mapping was also used to revise existing surficial geological mapping. Together, this map development better defines the surficial map unit boundaries and reflects the thickness variations in the deposits that are susceptible to amplification. To investigate this potential amplification, surface and subsurface shear velocity (Vs) data was compared with earthquake recordings.

The project also gives an update to the shear velocity (Vs) model for shallow geological materials, as compared to the already mentioned previous study.

The project concluded that, within the project area, susceptibility to amplification of seismic waves is widespread, occurring where the thickness of sediment over bedrock exceeds five metres. More specifically, the highest amplification may occur between five and fifteen metres thickness, where amplification of specific frequencies due to resonance can occur. Where the thickness exceeds fifteen metres, amplification can occur over a wide range of frequencies.

Geoscience BC Manager, Energy and Water Randy Hughes said: "The new maps and data generated by this project are giving a better understanding about which areas have the potential for increased ground motion during induced seismicity events associated with natural gas extraction. By sharing this information with industry, regulators, communities in the Peace River Regional District and Indigenous groups, it can be used to improve industry procedures to manage felt events."

Accessing Data
To view the reports and maps, visit the project pages or view the information on the Earth Science viewer online mapping application.

View project page          View project in Earth Science Viewer

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For more information, please contact:

Richard Truman
Geoscience BC