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17 Cards in this Set
- Front
- Back
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Describe the global distribution of earthquakes and how often quakes of various magnitudes occur
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In BC: 1600/year, 4-5/day
Worldwide: Great quakes/year 0-1 Major quakes/year 10-20 Strong - 134 avg. Moderate - 1319 avg. Light - ~13,000 avg. Minor - ~130,000 avg. Very Minor - ~1,300,000 avg. |
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Understand the different types of faulting at different plate boundaries, and which plate boundaries produce the largest quakes
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- Oceanic(fast, young) vs. Continental Plates(old, slow)
- Divergent - Tension, spreading plates -->smallish quakes - Transform - shear, sliding past --> Many quakes, moderate to large. But not as large as a convergent boundary - Collision Boundary or Subduction Zone - compression --> Continental Collision or Subduction Zone(Ocean|Ocean or Ocean|Cont.) -->Extensive small to very large quakes, where the largest occur |
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Describe how the Earth builds, stores, and releases energy in earthquakes (elastic rebound)
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Elastic rebound theory
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Elastic rebound theory
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Preexisting fault is held stationary (locked) by frictionBut elastic plastes ("blocks") on either side are moving slowly relative to each other
- Leads to distortion (deformation) of the blocks - Since they're elastic, shear stress gradually builds up - Quake starts at point "hypocenter" or "focus". Two blocks slide past each other. Most cases: stop immediately and tiny quake -In a large Quake, fault breaks, elastic strain and shear stress decrease |
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Understand concepts of (1) stress causing strain and (2) plastic versus brittle deformation
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Stress can be different forces in different directions. Change of shape or volume of an object under stress is strain. Pressure is uniform magnitude, all direction.
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Describe how the rupture propagates from the focus and why shaking and damage are not necessarily greatest at the epicenter
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Water ripples spreading out
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different types of seismic waves and how they move through the Earth
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- body waves
- surface waves - P wave - S wave |
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Body wave
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travel inside the earth
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Surface waves
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travel along boundaries between materials. Slower than body waves
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P wave / primary
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Particles move in same direction as the wave
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S wave / secondary
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Particles move perpendicular to wave. Cannot pass through fluids. Slower than P waves.
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Describe how an earthquake is recorded and how to locate the epicenter
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- Seismograph ("geophone")
- To locate epicenter: -Calculate distance to quake from 3 seismographs -Draw a circle around each and find where they intersect |
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Understand how local ground conditions can affect the duration and amplitude of shaking
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For larger earthquakes amplitude is greater, last longer, lower frequencies
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Explain factors that determine earthquake intensity
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1. Earthquake magnitude
2. Ground type 3. Distance from epicenter 4. Duration of shaking (this is not really independent of 1-3 above) |
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Be aware of how earthquakes can be the cause of other natural disasters (e.g., tsunamis, liquefaction, landslides)
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Liquefaction: Soil temporarily loses strength and flows like a liquid
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Understand the basics of how buildings can be designed or retrofitted to better resist earthquakes (and reduce casualties)
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Base isolation lets the ground move under the building
Dampers absorb energy in the building frame transmitted from moving ground Moment resisting frame is a 3d framework of beams and columns Identify fault zones that could produce an earthquake damaging to Vancouver.Explain what we can and cannot predict about large earthquakesKnow the difference between forecasting and prediction |
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Identify fault zones that could produce an earthquake damaging to Vancouver.
Explain what we can and cannot predict about large earthquakes Know the difference between forecasting and prediction |
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