Abstract

The 28 October 2012 Mw 7.8 Haida Gwaii earthquake was the second largest earthquake instrumentally recorded in Canada’s territory and was strongly felt across the British Columbia north coast (BCNC) region. Data from the Haida Gwaii sequence and other events in the region are compiled for 56 earthquakes between moment magnitude Mw 4.6 and 7.8 that occurred between 1996 and 2014. Pseudospectral accelerations (PSA) at 5% damping are calculated and compared against several modern ground‐motion models (GMMs) using different binning criteria (e.g., distance, magnitude, mechanism, source‐to‐site azimuth, and event chronology). Overall, no single model is found to be appropriate for the BCNC region, with GMMs generally overestimating recorded near‐source (i.e., <100  km) ground motions by factors of 2 or more across most of the spectral period range.

Earthquake motions recorded prior to and including the 2012 Mw 7.8 earthquake were generally more comparable with some GMMs at longer spectral periods but still possessed significant biases based on residual analyses. Additionally, earthquakes with normal mechanisms gave less short‐to‐mid‐period shaking relative to strike‐ and reverse‐slip events.

Online Materials: Summary of the candidate ground‐motion prediction equations, indicating their distance metrics and conditions of use.

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