Two significant historically active seismic zones occur along this system associated with northwest trending intersecting graben structures. The Charlevoix region has been the location of at least five magnitude six or larger earthquakes over the last 350 years, including the 1925 Charlevoix-Kamouraska earthquake. At the Lower St Lawrence zone the largest recorded earthquakes are about magnitude five. Seismic studies indicate a crustal convergence across the Saint Lawrence valley of about .5 mm (0.020 in) per year.
^Mazzotti, S.; Henton, J.; Adams, J., Crustal strain rates and seismic hazard from seismicity and GPS measurements along the St Lawrence Valley, Quebec, American Geophysical Union, Spring Meeting 2004, abstract #S14A-02 http://adsabs.harvard.edu/abs/2004AGUSM.S14A..02M