Abstract

Continuous monitoring of the seismically active Charlevoix zone since late 1977 has delineated the boundaries of the earthquake zone under the north shore and has enabled an association to be made with surface mapped faults that strike along the St. Lawrence Valley and dip to the southeast. Within the active zone, aseismic volumes are found under parts of the St. Lawrence River and another elongated zone of activity is found to the southeast on unmapped faults dipping under the river. The previous suggestions that the activity is related to old rift faults, which have been later weakened by a meteor impact, would seem to be upheld.

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