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32 Cards in this Set
- Front
- Back
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How earthquakes are generated
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1. Rocks slowly deform, storing, elastic energy
2. Eventually friction is overcome 3. Slippage occurs 4. Energy is released as the rock “springs back” into its original shape 5. Energy travels as seismic waves through the earth and along the surface of the Earth |
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The three different types of faults:
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Normal Fault: hanging wall goes down relative to footwall
Reverse Fault: hanging wall goes up relative to footwall Strike-Slip Fault: no vertical motion, one block slides sideways (laterally) past the other, fault surface is nearly vertical |
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Elastic Rebound Theory
-elasticity |
Elastic Rebound Theory: (elasticity – material deforms when under stress, but when that stress is removed, material rebounds ex: rubber band)
Explains how an earthquake is formed 1. Rocks slowly deform, storing energy 2. Eventually friction is overcome 3. Slippage occurs 4. Energy is released as the rock “springs back” into its original shape • Two tectonic plates moving steadily past each other but there is friction between the plates, eventually the friction is overcome and the two plates break apart but both parts look exactly the same, just slipped apart from each other = springing back to original shape because still look the same as before but broken apart |
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Stick-Slip Behavior
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start-stop movement on a fault
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The four different types of seismic waves and how they behave
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Compressional Wave: back and forth vibration direction (p-wave) -- travels through the Earth
Shear Wave: up and down vibration direction (s-wave) -- travels through the Earth Love Wave: side-to-side vibration direction Rayleigh Wave: like circles vibration direction |
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How seismic waves are measured:
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Seismograph - put under the Earth to measure seismic waves and put into the ground so background waves like a truck passing do not affect it
• Put under the Earth to measure seismic waves and put into the ground so background waves like a truck passing do not affect it • Need three stations to indicate their size and location |
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Why seismic waves are measured:
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To find the epicenter of an earthquake--- measured by time
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The difference between intensity and magnitude:
-Mercalli intensity scale -Magnitude |
Mercalli intensity scale - measure of quake’s destructiveness
Magnitude – of an earthquake is a number that indicates its relative size, as determined by measuring the maximum amplitude of ground motion recorded by a seismograph at a given distance from the epicenter |
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What is used to calculate earthquake magnitude:
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Richter Scale
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Some of the factors that determine the destructiveness of an earthquake:
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1. Building Codes = buildings that can withstand shaking – depends on economy - if city has a good economy then they will have better and more effective building codes
2. Depth of quake = shallow quakes cause more damage 3. Distance from focus 4. Rock type/sediment 5. Population density 6. Size and duration of quake 7. Time and date of quake |
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Ways that earthquakes can cause damage:
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• Buildings destroyed
• Roads/bridges collapse • Fires • Tsunamis • Liquefaction- fluid saturated unconsolidated material -Landslide/avalanche |
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Where earthquakes are most likely to occur:
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Quake probability: Based on location of seismic zones and recurrence interval
-Most quakes occur on seismic belts - along plate boundaries -Quakes that are not on boundaries are called intraplate quakes Divergent - shallow focus Convergent - shallow, medium, deep Transform - shallow |
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What can be done to mitigate earthquake hazards:
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• Educating the public & personal preparedness
• Engineering quake-resistant structures |
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If earthquakes can be predicted:
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• City plans, evacuation routes, fire/water planning
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Aftershock
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– small earthquakes that follow a major earthquake, may occur for days to several weeks
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Arrival time
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the instant at which an earthquake wave appears at a seismograph station
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Body waves
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pass through the interior of the Earth (p and s waves)
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Displacement
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– the amount of slip, on the fault
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Epicenter
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the point on the surface of the Earth that lies directly above the hypocenter
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Fault
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a fracture on which sliding occurs
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Focus
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the place in the Earth where rock ruptures and slips, or the place where an explosion occurs of the earthquake
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Foreshock
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smaller earthquakes before a major one
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Intraplate earthquakes
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some earthquakes occur in the interiors of plates and are not associated with plate boundaries, active rifts, or collision zones
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Liquefaction
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– the abrupt loss of strength of a wet sediment (either sand or clay) in response to ground shaking
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P-waves
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– (P stands for primary) are compressional body waves
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Recurrence interval
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– the average time between successive events
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Richter scale
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detailed guidelines for determining magnitude
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S-waves
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(S stands for secondary) are shear body waves
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Seismic gaps
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Seismic gaps – where a known active fault has not slipped for a long time, could be dangerous
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Seismogram
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Seismogram – can systematically record the ground motion from an earthquake happening anywhere on Earth
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Surface waves
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Surface waves – waves that travel along the Earth’s surface
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Tsunami –
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Tsunami – a series of giant waves
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