western quebec and southern ontario - Department of Geology

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$Fayek & Kyser 2000 uraninite fractionations.pdf - Queen's University$

Previous studies have suggested that earthquakes along the southwestern marginof the WQSZ zone demonstrate a reverse-sense reactivation of Paleozoic normal faultswithin the Ottawa-Bonnechere Graben (e.g., Kay, 1942; Adams and Basham, 1991; Bentet al. 2002). However, most earthquakes in the north-eastern part of the WQSZ have notshown any spatial relationships with the surface features of Grenvillian shear zones orany other rift-related faults (Forsyth, 1981; Adams and Basham, 1991). Previous authorshave proposed hypotheses relating pre-existing tectonic structures, includingMesoproterozoic shear zones associated with the Grenville orogeny (Forsyth, 1981) andlate Precambrian and early Palaeozoic normal faults associated with the Ottawa-Bonnechere Graben (Adams and Basham, 1991; Bent et al., 2002), to earthquakelocations. However, the nature of seismicity in the WQSZ is not well understood mainlydue to the lack of realistic models relating the earthquakes within the region to the mainseismogenic structures of the WQSZ. One of the reasons for this is probably the largeerror in the routinely calculated epicentres (~ 0.03° average error for the latitude andlongitude and a default depth of 18 km for most of the earthquakes in the GSC catalog).Some events in this zone have more accurate hypocentre locations but they do not coverthe whole area nor long period of time.2.3.2 The Charlevoix Seismic zone (CSZ)The Charlevoix region, located in southern Quebec along the St. Lawrence River 150 kmNE of Quebec City, is historically the most active earthquake zone in eastern Canada (e.g.Buchbinder et al. 1988) (Figure 2.3). This region has been monitored by a microseismicarray since 1977, yielding accurate locations of earthquake hypocentres. Large historical17
earthquakes have occurred within the St. Lawrence valley in the Charlevoix seismic zonenortheast of Quebec City in 1663 (M~ 7; Basham et al. 1979), 1791 (M~ 6), 1860 (M~6), 1870 (M~ 6.5) and 1925 (M~ 6.2).The Charlevoix seismic zone is structurally controlled by the Iapetan rift and ameteorite impact structure (Adams and Basham, 1991). Lamontagne et al. (2004) statedthat this region was cut by faults created during four tectonic events: the Grenvilliancollision (1100 to 900 Ma), the rifting episode related to the opening of the Iapetus ocean(700 Ma), the Taconian reactivation of these faults at the closing of the ocean, Mesozoicextension/rift related to Atlantic opening (450 Ma), and the meteorite impact (350 Ma).The CSZ contains part of a meteorite crater with a diameter of 54 km, consisting of abasin with a central uplift. This structure was identified as a meteorite crater in 1965 withthe discovery of shatter cones. Lamontagne (1987) proposed that the meteor impactweakened the rift faults, although meteor impacts are not generally associated with highlevels of seismicity (Solomon and Duxbury, 1987). Earthquakes in this zone are mainlythrust, or combination of thrust and strike-slip, events (Lamontagne, 1999) and theseismicity seems to be clustered along a segment of the St. Lawrence rift, which isoverlapped by the meteorite impact crater (Baird et al., 2009). This localization can beexplained by low-strength bounding faults and stress channelling between them (Baird etal., 2009).2.3.3 The Lower St. Lawrence Seismic Zone (LSZ)The LSZ is located at the estuary of the St. Lawrence River, between Baie-Comeau andSept-Iles (Figure 2.3). This zone is known as the third most active seismic zone in18
Page 1 and 2: FOCAL MECHANISMS AND VARIATIONS IN
Page 3: Acknowledgements:I would like to ex
Page 9 and 10: Figure 5.12: Summary of the focal m
Page 11 and 12: AbbreviationsCNSN: Canadian Nationa
Page 13 and 14: Earthquakes in western Quebec and s
Page 15 and 16: 1.2 Organization of ThesisChapter 1
Page 17 and 18: eastern Canada each year, of which
Page 19 and 20: Metasedimentary Belt boundary tecto
Page 21 and 22: The Grenville Front tectonic zone (
Page 23 and 24: Figure 2.3: Seismicity in the study
Page 25 and 26: oadly similar continent-continent c
Page 27: Figure 2.4: Historical earthquakes
Page 31 and 32: cluster, which is considered part o
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Page 35 and 36: CHAPTER 3DATA SET AND METHODS3.1 In
Page 37 and 38: Fig. 3.1: Locations of seismic stat
Page 39 and 40: Figure 3.2: Number of stations used
Page 41 and 42: the strongest recorded event in the
Page 43 and 44: Figure 3.5: Earthquake source param
Page 45 and 46: The amplitudes of the seismic waves
Page 47 and 48: Figure 3.7: Vertical component wave
Page 49 and 50: HYPOCENTER programThe HYPOCENTER pr
Page 51 and 52: wave - e.g. Pg or Pn, Sg or Sn), th
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Page 55 and 56: CHAPTER 4RESULTSIn this chapter the
Page 57 and 58: Figure 4.1: Distribution of RMS of
Page 59 and 60: Table 4.2: Earthquake parameters (h
Page 61 and 62: The focal depth calculated here is
Page 63 and 64: focal mechanism beach-ball diagrams
Page 65 and 66: some spatial variability of the ori
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Page 69 and 70: a)b)c)d)Western QuebecSouthern Onta
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Page 73 and 74: source region (e.g. Chen and Molnar
Page 75 and 76: estimate using a stress inversion t
Page 77 and 78: Figure 5.3: Stress pattern for all
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oundaries of the Central Metasedime
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In Western Quebec Seizmic Zone (WQS
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deeper than 20 km (20 km to 26 km).
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Figure 5.7: Geologic features of WQ
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2009). The Mont-Laurier earthquake
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a) b)c) d)Figure 5.9: Summary of th
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5.4.3 Adirondack Clusters (WQ4 and
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WQ5 is located in the southern part
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Figure 5.13: Geological features of
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consistent with regional fault map
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WQ8 is locatedin the north-western
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5.4.5 Timiskaming Cluster (WQ9)The
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The known faults in WQ9 cluster are
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a) b)c) d)Figure 5.19: Summary of t
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ecorded within this cluster. As it
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Figure 5.22: Nodal plane strike for
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estricted to western Lake Ontario o
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More detailed look at the relations
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Baird, W.A. F., and McKinnon, S. D.
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Easton, R. M. (1986). Geochronology
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Havskov, J., and Ottemöller, L. (2
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Ma, S., and Adams, J. (2002). Estim
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Rimando, R. E., and Benn, K. (2005)
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Wahlstrom, R. (1987) Focal mechanis
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APPENDIX A: Examples of Input and O
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SUNO BZ SN 3 141 15.29SADO BZ SG 4
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EEO BZ SG 4 140 48.02 91 0.09 0 315
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PAL BZ PN 2 D 140 33.20 53 -0.21 1
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APPENDIX C: Faults Plane Solutions
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Appendix D: Focal Mechanisms From P
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19810707 -74.6 45.1 13.0 1.9 304.0
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19950603 -76.4 47.1 18.0 3.9 100.1
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20060225 -75.2 45.7 18.7 4.5 125.8
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