SP 44 Chapter 22: 2-D and 3-D GIS Methods Applied to Earthquake Research The Charlevoix Seismic Zone, Quebéc
by J.R. Harris, M. Lamontagne, P. Keating, K. Sprague and T. Toutin.
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This chapter is from GAC's Special Paper 44: "GIS For the Earth Sciences" editted by Dr. Jeff Harris. To purchase the entire book in hardcopy or disc formats, please see the Special Papers section of our bookstore.
ABSTRACT: The spatial relationship between interpreted lineaments, mapped faults and epicentres is assessed using both 2-D and 3-D analyses. The 2-D analysis is undertaken over a broad region of central Québec. The proximity of epicentres to lineaments and faults is assessed using the weights-of-evidence (WofE) spatial analysis technique. A regional seismic potential map, based on structural and lithological parameters that were found to be spatially associated with epicentres, using WofE, is produced. The 3-D analysis, in which fault dips and the depth of earthquakes (hypocentres) are considered, is focused on the Charlevoix Seismic Zone (CSZ). The 3-D visualization and analytical tools together with WofE, are used in the analysis of faults, lineaments and hypocentres in the CSZ.
Many of the evidence maps used in the regional model are, at best, only mildly predictive of the known earthquakes. The strongest predictors are major NW, NE, EW lineaments interpreted from the remotely sensed and geophysical data. The 3-D analysis suggests that the rift faults on the north shore of the St. Lawrence River dip (45-70°) to the SE, and the faults/lineaments on the south shore dip very steeply (80°) toward the NW, creating a V-shaped "graben" structure. A 3-D analysis indicates that the earthquakes do not concentrate only on planar structures but define depth-limited volumes of enhanced activity. In this context, most large faults seem to bound these active volumes.
Geological Association of Canada
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