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 Earth Sciences Sector > Priorities > Canadian Hazards Information Service > Earthquakes Canada |
Charlevoix Seismic Zone, Canada
Lamontagne, M. and Ranalli, G. 1997. Faults and spatial clustering near La Malbaie, Charlevoix Seismic Zone, Canada. Seismological Research Letters, 68, no. 2.
The Charlevoix Seismic Zone (CSZ) is the most active area of Eastern Canada with more than 1500 earthquakes (magnitudes from about 0.0 ML to 5.0 mbLg) recorded between 1978 and 1995. Earthquakes of a sub-area of the CSZ were analyzed to find evidence of event clustering and of correlations with geological features. Out of 37 events recorded between 1988 and 1995, two triplets had high correlation coefficients and may represent repeated slip on the same fractures. Focal mechanisms of the two largest earthquakes of the sub-zone (magnitude mN 4.0 and 3.3) are consistent with the region's predominant reverse faulting regime. For these two events, nodal planes trend WNW-ESE, parallel to lineaments related to the Charlevoix meteor impact structure, in contrast with the generally assumed association with paleorift faults. For smaller events, discrete and composite focal mechanisms show variable trends and complex faulting styles including normal faulting and strike-slip. This complexity implies that small magnitude earthquakes could be related to local stress/strength variations, possibly in areas where high pore-fluid pressures are present.
