The seismicity of northern Canada

The addition of over 1000 earthquakes to the northern Canadian data file during the past 3 years provides sufficient data to delineate distinctive patterns of seismicity, although the short history of low level earthquake monitoring and the temporal and spatial clustering of earthquakes suggests that not all potentially active areas may yet have been identified. The data indicate areas of activity near the larger earthquakes located teleseismically prior to the post-1960 northern expansion of the Canadian Seismograph Network and additional clusters and trends that were not previously apparent. Correlations to seismicity with major deformational trends in the Yukon – Mackenzie Valley, the northern continental margin, the Arctic archipelago and encircling much of the Baffin Island – Foxe Basin area show that structures formed or reactivated by Palaeozoic and later orogenic phases are continuing activity in response to the contemporary stress field.Possible zones of Cenozoic movement show pockets of high seismic activity but important gaps in the trends remain off Banks Island, along Nares Strait, and in Davis Strait. Tectonic forces characteristic of plate margins do not appear to be acting in the Canadian Arctic, and contemporary movement of Greenland with respect to Baffin Island does not need to be invoked to explain the seismicity in the Baffin region.Epicentre clusters in the Beaufort Sea and offshore of Ellef Ringnes Island are distributed mainly over the seaward gradient of elliptically shaped free air anomalies, indicating seismic adjustment in basement structures to uncompensated wedges of Recent–Tertiary sediments. Seismicity around much of the Baffin Island – Foxe Basin block shows a significant correlation with the interval of isostatic equilibrium between broad areas of current postglacial uplift. If northeastern Baffin Island is a hinge zone in the rebound process, and the zone from Hudson Strait to northeastern Keewatin a line of inflection in the rate of uplift contours, the reactivation of structures is occurring along zones of high differential stress.