Coseismic Coulomb Stress Changes on Intraplate Faults in the Western Quebec Seismic Zone Following Three Major Earthquakes in the Past Century

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 the 1935 M_W 6.1 Témiscaming, 1944 M_W 5.8 Cornwall-Massena, and the 2013 M_W 4.7 Ladysmith earthquakes, which are proximal to faults in the WQSZ that exhibit a relatively high reactivation potential, to determine if they have an increased potential for 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 M_W 6.1 Témiscaming earthquake caused extensively positive ΔCFS (≥ 0.1 Bar) on its receiver fault. The areal extent of the receiver fault that has been promoted to failure suggests that earthquakes with a comparable magnitude to the 1935 event can be triggered. 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.