Low Probability Ground Motions for a Proposed Dam Site in Northeastern BC

The proposed dam site is located east of the Northern Rocky Mountain Trench and cordilleran deformation front in a region of relatively low seismicity. The region east of the site has been relatively quiet without any significant natural earthquakes until 2001, when a M5.4 Dawson Creek occurred approximately 70 km southeast of the site. This earthquake changed the potential for moderate to large earthquakes east of the deformation front. However, no active fault is known to exist nor have they been mapped. The local earthquakes close to the site are dominated by relatively small magnitude induced earthquakes due to oil and gas activities in the region. Alternative source zone models were developed to capture the epistemic uncertainties in the hazard due to the natural and induced earthquakes. A probabilistic approach with a logic tree to treat epistemic uncertainties was used to estimate low probability ground motions at the site. As the site is influenced by both Western and Eastern North American type sources, a suite of ground motions prediction equations representative of both conditions were used. The estimated 1/10,000 Annual Exceedance Probability (AEP) Peak Ground Acceleration (PGA) at the site is 0.23 g.

Thavaraj, T. and A. Sy. 2015. “Low Probability Ground Motions for a Proposed Dam Site in Northeastern BC,” in Proceedings of the 11th Canadian Conference on Earthquake Engineering (11CCEE), July 22-24, 2015. Paper No. 94178, p.10. Victoria, BC: Canadian Association of Earthquake Engineering.