96 Cards in this Set
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Where do earthquakes occur?
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Most earthquakes occur along plate boundaries, but they can also occur in the interior of plates
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What is an earthquake?
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Vibration of the earth caused by a rapid release of energy
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What causes earthquake?
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Slip along a fault, volcanoes, landslides, extraterrestrial impacts, bomb explosions
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Elastic Rebound #1
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Stress is applied
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Elastic Rebound #2
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Strain energy accumulation (deformation)
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Elastic Rebound #3
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Rock breaks
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Elastic Rebound #4
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Energy is released -> seismic waves
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Focus
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The location underground where the fault first breaks; body waves are generated in this location
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Epicenter
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The location on Earth's surface directly above the focus
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Fault Scarp
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The feature formed where a dip-slip fault produces offset at the surface of the Earth
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Foreshocks
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Small to moderate earthquake that occurs before and in the same general area as the main earthquake
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Main Shock
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The primary, highest magnitude earthquake in a series of earthquakes in a given area
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Aftershocks
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Smaller earthquakes that follow a large magnitude main shock
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Seismic Waves
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Sudden rupture of rocks producing shock waves called
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Body Waves
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Primary Waves and Secondary Waves
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P-Waves Speed
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4 miles/sec
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P-Waves Movement
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"Slinky"; Compressional waves, push-pull waves
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Vibration is parallel to the direction of travel
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P-Waves
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Move through solids and liquids
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P-Waves
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P-Waves Feel
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Sharp vertical jolt
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S-Waves Speed
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2 miles/sec
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S-Waves Movement
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"Snake"; Shear waves, side to side motions
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Vibrate perpendicular to travel direction
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S-Waves
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Cannot travel through liquids
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S-Waves
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S-Waves Feel
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Side to side
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Slowest Waves, Most destructive, Lots of different motion
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Surface Waves
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Arrive after body waves
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Surface Waves
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Seismograph
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Instrument that records earthquakes
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Seismometer
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Modern version of Seismograph
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Seismogram
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The written record that records the motion of seismic waves
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Magnitude
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A quantitative (numerical) measure of earthquake size
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Each increase in Magnitude results in ____x more shaking
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10
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Each increase in Magnitude results in ____x more energy
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32
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The original magnitude scale, developed in 1935
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Richter Scale
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Determined by one seismogram and two measurements:
a. distance to epicenter (S-P wave arrival time)
b. amplitude of maximum shaking
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Richter Scale
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Based on amount of shaking (effects of earthquake), Logrithmic scale
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Richter Scale
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The modern magnitude scale used today by seismologists to measure earthquake size
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Moment Magnitude Scale
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Determined by measurements of the cause:
a. fault rupture area (Length x Width)
b. amount of slip along the fault
c. rock strength (type of rock)
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Moment Magnitude Scale
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Based on release of energy
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Moment Magnitude Scale
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Intensity
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A qualitative measure of earthquake size
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Determined by 12 levels of intensity:
I-XII
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Modified Mercalli Intensity Scale
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Based on effects of the earthquake; damage human response
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Modified Mercalli Intensity Scale
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Magnitude (amount of energy released)
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Factor controlling the intensity of ground shaking #1
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Distance from the epicenter
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Factor controlling the intensity of ground shaking #2
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Depth of earthquake focus
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Factor controlling the intensity of ground shaking #3
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Direction of rupture - directivity
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Factor controlling the intensity of ground shaking #4
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Ground material
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Factor controlling the intensity of ground shaking #5
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Most shaking (1-3)
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Wed mud/silt
Dry mud/silt
Sand
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Least shaking (3-1)
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Alluvium (gravel, cobbles, boulders)
Sedimentary bedrock
Igneous/Metamorphic bedrock
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Highest magnitude earthquake ever recorded?
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1960 Chile; M 9.5
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Most damage in earthquakes caused by
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Ground Shaking
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Liquefaction
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Conversion of water saturated sand from solid into liquid
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Liquefaction - how?
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Vibrations from seismic waves increase water pressure in the spaces between sand grains
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Landslides
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Loose material is dislodged during ground shaking and moves downslope
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Example of Landslide
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Turnagain Heights in Anchorage, Alaska
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Liquefactions
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Causes of floods
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Landslide in river
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Causes of floods
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Water pipes/ water mains break
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Causes of floods
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Dam/level failure
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Causes of floods
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Tsunamis
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Causes of floods
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Example of Flooding
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"Quake Lakes" in China
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Electrical lines break
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Causes of Fires
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Candles/ Stoves/ Fireplaces
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Causes of Fires
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Gas Station/ Oil Refineries
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Causes of Fires
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Explosions
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Causes of Fires
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Electrical Shorts
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Causes of Fires
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Matches/lighters
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Causes of Fires After Earthquake
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Roads blocked
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Why do fires burn so long?
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Water lines broken
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Why do fires burn so long?
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Lots of fuel
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Why do fires burn so long?
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Lots of fires become big fires
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Why do fires burn so long?
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Emergency services are busy
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Why do fires burn so long?
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Example of Fires
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1906 San Francisco Earthquake
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Lack of clean water
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Causes of Disease Outbreak
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Hospitals overwhelmed
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Causes of Disease Outbreak
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Shelters overwhelmed
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Causes of Disease Outbreak
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Pipes breaking sewage
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Causes of Disease Outbreak
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Tsunami (Seismic sea waves)
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Produced by a large underwater megathrust earthquake
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Causes of tsunamis
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Landslides (underwater landslides or landslides into the ocean)
Asteroid impacts
Volcanic eruptions
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Earthquake cause of tsunamis
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Must be underwater
Must cause vertical displacement along the ocean floor
Must be large magnitude (Subduction zones megathrust)
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Wave Speed in Deep Ocean
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450 mph, 720km/hr
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Wavelength in Deep Ocean
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60 miles
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Amplitude in Deep Ocean
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3 feet
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Wave Speed Near Shore
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30 mph, 50 km/hr
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Wavelength Near Shore
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4 miles
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Amplitude Near Shore
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Less than 100 feet
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What does a tsunami look like?
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Like sea level rises very fast; may look like an advancing wall of water
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How far do tsunamis travel in the ocean?
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For miles; until they reach land
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How far do tsunamis travel on land?
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Depends on the topography
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What to do if a tsunami is coming?
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Go to higher ground
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Rapid water withdrawal
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Warnings of Tsunami
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Odd animal behavior
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Warnings of Tsunami
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Earthquake
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Warnings of Tsunami
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Warning sirens
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Warnings of Tsunami
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2004 Indian Ocean Tsunami
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Example of Tsunami
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2011 Tohoku Tsunami
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Example of Tsunami
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GLG 112: EXAM 1