Amplification of Seismic Ground Motion Hazard Mapping for the Fort St. John – Dawson Creek Area

Key Researcher(s):  P. A. Monahan

Project ID:  2018-052

Key Research Organization(s):  Petrel Robertson Consulting Ltd.

Project Location:  Northeast BC

Focus Area:  Energy-Oil and Gas

Summary



With a focus on the populated Fort St. John-Dawson Creek area, where hydraulic fracturing and fluid injection by the petroleum industry is a concern for public safety, this project will provide new information on how and where seismic waves travelling through soils and sediments below the surface may be amplified, generating necessary information for regulators and industry to reduce risk by improving protocols.

The Need

Buildings and public infrastructure in BC are built to specific engineering building codes to withstand ground motion, but the presence of certain sediments and geological conditions can amplify non-threatening seismic waves to ones which could potentially be a threat to public infrastructure.

Some softer soils, sediments and geological conditions found in the Peace Region of northeastern BC have the potential to amplify ground motions. In a manner similar to ocean waves slowing down and increasing in height as they approach the shore, seismic shear-waves increase in amplitude as they slow down in near-surface sediments. This has the effect of amplifying ground motion.

With an increase in seismic activity from hydraulic fracturing and fluid injection at oil and gas sites in northeast BC, it is important to understand how and where this can occur so that any risk can be reduced and managed.

This project builds on a regional study completed in early 2019 by collecting more detailed subsurface information for a smaller area, where the majority of the population in the Montney play – the name given to the large sedimentary basin that hosts oil and gas resources in this area – is concentrated.

Project Goals

To collect and interpret new subsurface geological and shear-wave velocity data to:

  • Prepare new geological and amplification susceptibility maps that reflect the thicknesses of unconsolidated deposits;
  • Improve the shear-wave velocity model for the shallow geological materials;
  • Provide shear-wave velocity measurements at seismograph stations, particularly those with apparently anomalous amplifications, as well as other sites where amplified ground motions have been reported, to better understand the controls over amplification of seismic ground motions.

Project Benefits

This project will provide more detailed mapping (than the previous project 2016-062) for predicting ground motion amplification and assess the induced seismic hazard to public and petroleum industry infrastructure in an area of the Montney Play where there is significant population and infrastructure.

It will also provide basic shear-wave velocity data (the wave that shakes the ground back and forth perpendicular to the direction the wave is moving) to refine the ground motion prediction equations and to inform ongoing research into seismicity induced by petroleum industry activity.

The maps and data will provide industry, regulators, communities and First Nations with a better understanding of the risks associated with ground motion in the Fort St John-Dawson Creek area.

The new information will be used by regulators and industry operators who are managing petroleum industry activity to improve processes and protocols to reduce risk of damage resulting from hydraulic fracturing and fluid injection by the oil and gas industry.

Survey Area

The Peace Region, including areas around Fort St. John and Dawson Creek, NE BC.