Earthquakes in the Eastern Canadian Arctic: Past Occurrences, Present Hazard, and Future Risk

Abstract

Abstract The Canadian Arctic encompasses several active seismic areas where a small number of significant earthquakes have been recorded since the early twentieth century. Our study area is defined as the eastern Canadian Arctic, an immense territory that covers 30% of the Canadian land mass. It includes the territory of Nunavut and the region of Nunavik in northern Quebec. Ten earthquakes had a moment magnitude (M) between 5.5 and 7.4, but only five can be considered significant because of their impact. Most were felt in communities at distances of a few hundreds of kilometers, but none exceeded modified Mercalli intensity (MMI) V. This article contains descriptions of the impact of these five earthquakes and of smaller ones that were felt in nearby communities. These macroseismic effects suggest stronger attenuation of MMIs than what is generally assumed for eastern North America. According to the current seismic zoning, very few communities face a significant earthquake hazard. Seismic risk has to consider that most high Arctic buildings are built on piles sitting on permafrost. It is believed that the newer engineered constructions would resist fairly well to seismic shaking, as opposed to buildings with older at grade foundations with little lateral resistance. The fast warming of the Arctic may lead to some thickening of the active layer of the permafrost, which may increase the potential for slope instabilities during earthquake shaking. The change would not be significant enough to alter the potential for local ground-motion amplification.