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Chapter 5-6.docx

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GOPH 375

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Midterm 1: 35-40 mc chapters 1-8 Chapter 5  Seismic risk = vulnerability X seismic hazard. Vulnerability increases with lots of population, tall buildings, highways etc  CNSN: Canadian National Seismograph Network monitors EQ activity o EQ’s trigger two rapid responses (within minutes): Automated Natural Hazard Alert System (ANHAS-alerts railways/utility companies, etc) and shake maps (representation of the ground shaking during an EQ)  Seismic zonation: Building codes to be EQ resistant – building materials that don’t cause resonance  Resonance: overlap between seismic wave’s natural frequencies and foundation buildings/materials. Your building resonance shouldn’t match the ground materials (earthquake frequencies at all)  BC has a large hazard for mega-thrust EQ  Canada’s Largest earthquake: Queen Charlotte Islands  Figure 5.2/5.4/5.3  Figure 5.13/5.17 (salt water killed the trees)  Intraplate earthquakes: not on plate boundaries, inside continent. Deformation forces, existing faults are reactivating, failing due to current stress and generating EQ (St. Lawrence River) o Supposed correlation between intraplate EQ epicentres that line up with fracture zones, o North American plate going over the Great Meteor Hotspot (thermal anomaly currently under NA plate)  Continents are rifted, drifted and reassembled in different patterns. Sometimes rifting process stops before separating a continent, leaving weak spots in continents and failed rifts  5.20 (Quebec along the St Lawrence valley river) – this is along an old plate rift. Even though there is no plate edge there now, there was one. Old boundary likely to have earthquakes  5.12: map distribution of the earthquakes?  Cascadia subduction zone: transform Queen Charlotte Fault Chapter 6 Volcanoes are the last section covered – chapter 8 1. Moment magnitude = area of rupture X elastic energy release/area 2. Wave equation a. Velocity = frequency X wavelength i. Period =1/frequency 3. Velocity = √ (gravity*depth) Tsunamis  6.1 examples and fatalities; Figure 6.16  Causes: o Earthquakes are most common cause; displaces a lot of water by displacing the ocean floor Vertical (dip) EQ displacements needed to move water into tsunami. More seismic gaps to fill means more EQ/tsunamis to come o Volcanic eruptions – jolts of energy into the water by exploding, collapsing or sending avalanches of debris into the water (fig 6.22) Indonesia. Thermal energy of magma converts to mechanical energy for tsunamis when in contact?  Flank collapses: whole side of an oceanic volcano breaks off &falls into the sea o Landslides – marine (under water) or sub-aerial (collapse happens above water and runs into the water; large water displacement). Hawaiian island chain - Collapse of continental shelf. Landslides and volcano tsunamis are like a rock dropped in water, energy fans out & weakens (EQ energy moves in perpendicular motion) therefore landslide/volcano tsunamis can be higher locally but don’t
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