1. Created by Michelle Vokaty and Ashten Sawitsky

2. Overview Tectonic setting Canadian/Quebec/CSZ Earthquakes Charlevoix Seismic zone and location Geology Sediment control Mercalli Scale Relationship of Magnitudes Historic, type, causes and effects of CSZ Earthquakes

4. Major Earthquakes in Canada

5. Earthquakes in the Quebec Region

6. Charlevoix Local Seismograph Network

7. Charlevoix Seismic Zone (CSZ) 100 km from downstream Quebec City Most seismically active region in Eastern Canada, defined by over 2000 local earthquakes between 1978 and 1997 Detectors record over 200 quakes a year Dominated by earthquakes along and in between the Iapetan faults (or otherwise known as the St.Lawrence Paleo-rift faults) Most activity occurs along the St. Lawrence valley

8. Historic Causes of CZS Quakes Four major events that are the cause for these earthquakes Grenvillian collision (110-900 Ma) Rifting due to opening of the Iapetus Ocean (700Ma) Then the reactivation of these faults when Iapetus stared closing during Taconian Orogeny (450 Ma) Finally, the Devonian Meteor impact (350 Ma) One controversial theory: Conditions such as high pore fluid pressure and/or low coefficient of friction must exist that do not exceed the maximum crustal stress differences

9. Location of 1870 EQ in Seismic Zone Quebec city is rated 6 th for earthquake risk and 1 st or 2 nd for damage Strong earthquakes with epicenter distances between 0-80km

10. Geology of Zone Four main geological assemblages 1.The Precambrian shield of Grenvillian age with charnockite-mangerite assembleges, metasediments, anorthosite intrusives and local gabbro dykes within the fault zones 2.Ordivician St. Lawrence platform- predominantly limestones 3.Appalachian nappes- Cambrian sedimentary rocks (sandstones, mudstones) which is thrust over the previous two 4.Quaternary deposits- usually glacial till and marine clays and valleys filled with multi-interglacial sedimentary sequences

11. Sediment controls Sand, clay, unconsolidated manmade sediment Thickness of 5-30m Thick deposits – Long period – More shaking – Most damage Rivers affect the area 1950 – Spring and Fall

12. Modified mercalli scale 12 increasing levels of intensity Imperceptible shaking to catastrophic destruction Arbitrary ranking based on observed effects Effects experience at the place Higher numbers=structural damage, lower number=felt by ppl

13. Rate vs. Magnitude

14. Types of Earthquakes High quality records used to study focal mechanisms, earthquake clusters and crustal velocities Earthquakes occur within the Precambrian lithology’s Upper to mid-crustal thrust strike-slip events No conclusive reasons/pattern for earthquakes

15. Earthquakes in history 1663 – M7, epicenter in CSZ, landslides 1791 – M6, Felt in Quebec City 1860 – M6, epicenter in CSZ 1870 – M6.5, felt in Quebec City 1925 – M6.2, epicenter in CSZ, damage in Lower Town 1988 – M5.9, MMI = V-VII

16. Factors of earthquakes Earthquake source (magnitude, focal depth, epicenter distance Characteristics of inhabited area (distribution of inhabited areas, characteristic of building stock, thickness and properties of underlying material Most damage in deep unconsolidated sediment (lower part of town) – Natural deposits and manmade fills are thickest Saint-Roch and Champlain wards effected Short epicenter distance=more damage

17. 1870 Geological/Economic Effects Caused geysers of water and sand Possibly relates to a sand volcano in Gouffre River Valley Only 1989 M 6.3 caused surface faulting, some say some offshore surface faulting could have occurred, although hard to see/record during that time-recent seismic data report negative results Few indirect casualties such as heart attacks, but more structural damage Possible geological effect is liquefaction

19. Bibliography John E. Ebel, M. D. (2013). Assessing the Location and Magnitude of the 20 October 1870 Charlevoix, Quebec, Earthquake. Seismological Society of America, 588-594. Lamontagne, M. (2002). An Overview of Some Significant Eastern Canadian Earthquakes and Their Impacts on the Geological Environment, Buildings and the Public. Natural Hazards, 55067. Lamontagne, M. (2008). Earthquakes in Eastern Canada: A Threat that can be Mitigated. Natural Resources Canada, 13-23. Lamontagne, M. (2009). Description and Analysis of the Earthquake Damage in the Quebec City Region between 1608-2008. Natural Resources Canada, 514-524. Lamontange, M. (1999). Rheological and Geological Constraints on the Earthquake Distribution in the Charlevoix Seismic Zone, Quebec, Canada. Natural Resourses Canada. Lamontange, M. (2008). Casualties Directly Caused by an Earthquake in Canada: First Contemporaneous Written Accounts from the M 6.5 Charlevoix, Quebec, Earthquake of 20 October 1870. Seismological Society of America, 1602-1606.