A re-examination of the 1925 Charlevoix, Québec, earthquake

The 1 March 1925 Charlevoix earthquake is one of the largest earthquakes known to have occurred in southeastern Canada. Because it occurred in one of the most active seismic zones of southeastern Canada, and near now heavily populated regions, understanding this earthquake may have implications for seismic hazard assessments of the region. Previous attempts have been made to study this earthquake using modern waveform analysis techniques, but the source parameters could be only partially constrained due to a lack of good data. Recently, a number of seismograms that had not been previously studied were rediscovered, warranting a second look at the earthquake. The best overall solution is strike 42° ± 7°, dip 53° ± 7°, rake 105° ± 10°, depth 10 km, seismic moment 3.1 ± 2.5 × 1025 dyne cm ( MW 6.2), MS 6.2 ± 0.3, mb 6.5 ± 0.4, source duration 5 sec, and stress drop 35 bars. The focal mechanism is consistent with many recent earthquakes in the Charlevoix seismic zone, but inconsistent with the regional stress field.