Research Article| October 01, 1980 The Charlevoix Earthquake of 19 August 1979 and its Seismo-Tectonic Environment* Henry S. Hasegawa; Henry S. Hasegawa Energy, Mines and Resources Canada, Earth Physics Branch, Division of Seismology and Geothermal Studies, Ottawa, Canada K1A 0Y3 Search for other works by this author on: GSW Google Scholar Robert J. Wetmiller Robert J. Wetmiller Energy, Mines and Resources Canada, Earth Physics Branch, Division of Seismology and Geothermal Studies, Ottawa, Canada K1A 0Y3 Search for other works by this author on: GSW Google Scholar Seismological Research Letters (1980) 51 (4): 23–38. https://doi.org/10.1785/gssrl.51.4.21 Article history first online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation Henry S. Hasegawa, Robert J. Wetmiller; The Charlevoix Earthquake of 19 August 1979 and its Seismo-Tectonic Environment. Seismological Research Letters 1980;; 51 (4): 23–38. doi: https://doi.org/10.1785/gssrl.51.4.21 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietySeismological Research Letters Search Advanced Search Abstract The focal mechanism has been determined for an intermediate-magnitude earthquake in the most seismically active region in Eastern Canada. On August 19, 1979, an mb (Lg) 5.0 earthquake occurred in the Charlevoix seismic zone, under the St. Lawrence River near the towns of St. Fidele and La Malbaie, Quebec. Maximum reported intensity in the epicentral region was MMV; the steepest gradient in the isoseismal contours is in a southeasterly direction, where there are northeast-southwest trending structures of the Appalachian Province. The P-wave nodal solution indicates thrust faulting on both nodal planes, in general agreement with the solutions from microearthquakes in the same epicentral region. Focal depth of aftershock activity has an average value of 9.5 km, with a spread of ±1 km; our preferred estimate of the focal depth of the main shock is 10 ± 2 km. From an analysis of surface wave data of the main shock, an estimate of focal depth falls in the range 6–11 km, in agreement with aftershok data. A mean value of the aftershock area is 3.5 km2, which is taken to represent the fault area of the main shock, and under the assumption of a circular fault, the stress drop of the main shock is estimated to be 50 bars. Because of the presence of zones of weakness in the epicentral area, the direction of maximum principal stress is only loosely constrained (within northeast to southeast quadrant). This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.
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Hasegawa et al. (1980) studied this question.