Correlation between Coulomb Stress Changes Imparted by Historic Earthquakes and Current Seismicity in Charlevoix Seismic Zone, Eastern Canada

Abstract

ABSTRACT The Charlevoix seismic zone (CSZ) is the most seismically active region in eastern Canada and has experienced several large historic events, such as the 1663 M 7 event (in which M is moment magnitude), as well as ongoing low‐level activity. Recent statistical studies (Fereidoni and Atkinson, 2012, 2014) suggest the contemporary seismicity in Charlevoix cannot be reconciled as part of a long aftershock sequence from the 1663 event. However, this does not eliminate the possibility that current seismicity in Charlevoix might still be influenced by stress changes related to the 1663 event. In this article, we investigate the correlation between the location of contemporary seismicity in the region and the static stress changes imparted by the 1663 earthquake. We model the 1663 earthquake as a primarily thrust event on a southeast‐dipping fault, which would have produced regions of increased stress that coincide with areas where current microseismicity is concentrated. With our assumed rupture model, we find that ∼75%–80% of the current seismicity (from 1978 to the present) is located in the area of positive Coulomb stress changes. The relatively good correlation between the models of static stress changes and the seismicity pattern observed in Charlevoix may suggest the background seismic activity in the region is still influenced by the stress perturbations due to the 1663 shock.