Abstract

On 27 October 2012, a magnitude (Mw) 7.8 earthquake occurred in the sparsely populated region of Haida Gwaii, British Columbia, Canada (formerly called the Queen Charlotte Islands). This was the second largest recorded earthquake in Canadian history. It was felt throughout British Columbia and as far away as the Yukon, Alberta, and Montana, roughly 1600 km from the epicenter. In some locations (notably on Haida Gwaii) the perceivable shaking lasted 1.5–2 min, with very strong shaking for about 30 s. Strong ground motions recorded at three locations in the region reached a maximum horizontal acceleration of 0.2g. Fortunately, this earthquake resulted in very limited damage partly because of the relatively large distance (more than 60 km) between population centers and the fault rupture and partly because of seismic resistance of the generally low, wood‐frame construction found on the islands. We examine the various physical effects from the shaking (e.g., tsunami, landslides, building damage, loss of hot springs), cataloged by field crews and reported by the inhabitants of Haida Gwaii and the surrounding regions. These will serve as a guide toward the potential impact from future large earthquakes on the various Haida Gwaii communities.

Through a Community Decimal Intensity evaluation of people’s accounts, it was revealed that, although intensities were close to expected near the source zone, regional intensities were lower than predicted by the conventional western North America theoretical relation.

Finally, the October 2012 earthquake may be used as a scenario event for moderate subduction earthquakes in other, more populated areas of British Columbia, Canada, and the world.

Online Material: Abridged “Did you feel it?” reports.

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