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western quebec and southern ontario - Department of Geology

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CHAPTER 1INTRODUCTION1.1 IntroductionEastern Canada is part <strong>of</strong> the stable interior <strong>of</strong> the North American plate. Our knowledge<strong>of</strong> the cause <strong>of</strong> seismic activity in Eastern Canada is far from complete. Regionalseismicity plays an important role in the study <strong>of</strong> tectonic processes <strong>and</strong> can contribute tothe underst<strong>and</strong>ing <strong>of</strong> the nature <strong>of</strong> these processes <strong>and</strong> to the evaluation <strong>of</strong> the seismichazard. Accurate locations for earthquake hypocentres are important in identifyingpotential seismogenic features <strong>and</strong> developing a relationship between seismicity <strong>and</strong> thetectonic structures <strong>and</strong> features. Other source parameters such as focal mechanisms canalso provide information on the tectonic structures on which the earthquakes occur. Theearthquake source parameters also provide information about the regional <strong>and</strong> local stressdistributions within the plates, as well as the geometry <strong>and</strong> kinematics <strong>of</strong> fault slips.Accurate estimation <strong>of</strong> the magnitude <strong>of</strong> the seismic events can also provide insight intothe size <strong>of</strong> the active faults. Earthquakes with magnitude <strong>of</strong> m N ≤ 3 have rupture sizes inthe order <strong>of</strong> 1-100 metres with slips <strong>of</strong> less than a few centimetres, while earthquakeswith larger magnitudes (m N > 5) may have rupture dimensions at the scale <strong>of</strong> kilometres(e.g. Johnston, 1993).1

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