ABSTRACT

Understanding the behavior of aftershock sequences is important to obtain a reliable evaluation of seismic hazard. It has been hypothesized that in continental intraplate regions, such as eastern Canada, aftershock sequences may persist for hundreds of years following a strong mainshock. In this study, we statistically characterize the behavior of aftershocks in the St. Lawrence valley, the most seismically active region in eastern Canada. The observed aftershocks of moderate recent earthquakes in the region are used to calibrate the parameters of the Reasenberg and Jones aftershock decay model. The average values obtained for the region fall in the range of the corresponding values of the parameters for earthquakes in California; however, the aftershock sequences in eastern Canada are less energetic on average, and one event (the 1982 Miramichi earthquake) had a longer‐than‐average aftershock sequence. We use aftershock models for the region, considering the range of parameters obtained from the moderate events, as well as the corresponding parameters for a generic California model, to compute the expected activity rates in the area of the 1663 Charlevoix earthquake, to gain insight into how much of the contemporary activity might be considered part of a prolonged aftershock sequence. We conclude it is very unlikely that contemporary seismicity in Charlevoix represents aftershocks from the 1663 earthquake.

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