Abstract

The limit of the direct effects of the Charlevoix astrobleme in the upper part of the Earth's crust outlines approximately a revolution paraboloid about a vertical axis. It reaches 14 km in depth below the center of the astrobleme and exhibits a 27 km radius at the present-day ground surface. The microearthquakes, which reflect the regional crustal stresses in eastern North America, occur on the normal faults characteristic of the St. Lawrence Lowland tectonic terrain mainly near the astrobleme paraboloid or near a second paraboloid located 7.9 km outside the first one. This second one could result from some yet undefined interference between the crust–mantle boundary and the shock wave responsible for the formation of the astrobleme 350 Ma ago. The very low seismic activity in the vicinity of Petite-Rivière–Saint-François may imply that energy is now building up in that area.

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