Coseismic Coulomb Stress Changes on Intraplate Faults in the Western Quebec Seismic Zone, Canada: Implications for Seismic Hazards

Abstract

There is currently no active fault map for the intraplate western Quebec seismic zone (WQSZ) in eastern Canada, and consequently, no detailed finite-fault source models which are critical for seismic hazard assessments in this region with a rapidly growing population. While previous numerical stress modelling studies have shown that mostly NNW-SSE to NW-SE-striking faults exhibit the highest potential for reactivation under the present-day tectonic stress field, such modelling is unable to take into account the interaction of faults and earthquakes. This study attempts to identify possible future rupture zones using Coulomb stress analysis. We explore the static stress transfer caused by select earthquakes (MW > 4.5) in the past century to proximal ‘receiver’ faults in the WQSZ, with a focus on those that exhibit a relatively high reactivation potential, to identify faults that have been promoted to failure. The significance of Coulomb stress changes (ΔCFS) observed on the nearby ‘receiver’ faults varied widely. Among the events analyzed in this study, only the 1935 MW 6.1 Témiscaming earthquake caused extensive positive Coulomb stress change (≥ 0.1 Bar) on its receiver fault. The modelled fault rupture extents suggest a range of earthquake magnitudes of MW 6-7. This work is the first attempt to provide a physical basis for seismic hazard assessment input parameters in the WQSZ based on the results of numerical stress modelling.