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51 Cards in this Set
- Front
- Back
CHAPTER 8
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Flash Cards
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Why do earthquakes occur on Earth?
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Because of the earths structure and plate tectonics
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What is the elastic Rebound theory
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Concept that earthquakes occur when rock elastically bends until it fractures, the fracturing generates earthquake energy and decreases the elastic energy stored in the rock
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Understand stick slip behavior of faults
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stop start movement along a fault plane caused by friction, which prevents movement until stress builds up sufficiently
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Understand earthquake cycle
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Rocks deform elastically then rebound during an earthquake rupture
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What happens during an earthquake?
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Rupture propogation and Wave propogation
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What is rupture propagation?
What is wave propagation? |
Rupture propogation- happens on faults, faults slipping spreads out along the surface
Wave propogation- causes ground shaking as earthquake energy travels as seismic waves. |
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Understand how DIRECTIVITY EFFECT and SEDIMENTARY BASIN EFFECT may affect ground shaking amplitude.
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D.E= stronger shaking in the direction of rupture propogation
S.B.E= Seismic waves decrease with propogation distance |
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What are body waves?
2 types? |
propogate through the interior of the earth (3D volume)
P WAVES= primary, fastest, compress/expand S WAVES= slower, second, shear shaking, solid only |
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What are surface waves?
2 types? |
Propogate near the surface, slower than body waves
L WAVES= love, move back/forth (snake) R WAVES= Rayleigh, moves like ripples on a pond |
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How does the ground shake due to different types of
seismic waves? |
On R Waves, particles underground follow a circular path as the wave passes.
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What is a seismograph?
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instruments recording seismic waves.
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Understand how to locate the epicenter of an earthquake from travel time observations of
three seismic stations. |
3 stations allow you to locate the epicenter, called triangulation.
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What is the difference between an intensity scale and magnitude of an earthquake
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Intensity scale is based on destructiveness while earthquake magnitude is determined from instrument measurements
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What measurable quantities are used to determine Richter magnitude and moment magnitude determined, respectively?
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Richter magnitude is based on max amplitude of ground movement.
Moment magnitude is based on seismic moment |
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How many times more energy release, respectively, for one unit difference in earthquake magnitude?
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1 unit increase in magnitude represents 32 times increase in energy release.
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how many magnitude 8 and magnitude 7 earthquakes occur a year?
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500 times
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• Where do most earthquakes occur? Where do intermediate and deep earthquakes occur?
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Most occur @ plate boundaries.
Intermediate and Deep earthquakes occur @ convergent boundaries |
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What is the fault that is the most active in US? Which two plates meet at this fault?
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San Andreas Fault.
Pacific plate meets North American plate |
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What is the maximum depth an earthquake can occur on Earth?
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up to 660 kilometers deep
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At what types of plate boundaries did 2010 Haiti, Chile, and Baja earthquakes occur?
What types of faulting occurred in these earthquakes? Compare their sizes in terms of magnitude and difference in energy release. |
Convergent
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What is liquefaction?
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water saturated sediments lose strength under shaking and behave like a liquid.
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• Understand how Tsunami waves behave differently in open ocean and near shoreline
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are imperceptible in deep water, waves grow in height as the water shallows
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How can long-term earthquake prediction be made? Is short-term earthquake prediction
feasible currently? |
avg the time between successive earthquakes (recurrence interval)
Short term earthquake prediction is not feasible. |
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• Why can seismic waves be used to explore Earth's interior?
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because they travel @ different speeds in different rocks (s waves only through solid!)
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How does seismic velocity
change with depth in Earth? |
8
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What evidence did seismologists use to discover Moho,
core-mantle boundary, and two-layer-structure of the Earth's core? |
Moho- P wave arrivals have different velocities @ different stations
Core mantle- P Waves do not arrive in the P wave shadow zone. 2 layer structure- S waves dont arrive in the s wave shadow zone and the p wave relection within the core |
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CHAPTER 9
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Flash Cards
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What are strain and stress in geology? Different kinds.
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Strain= with distortion only
ex(stretching, shortening,shear) Stress= cause of strain ex(compression, tension, shear stress) |
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What does orogeny mean?
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a Mountain building event
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What are the two main types of deformation and determinant factors?
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9
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How do joints and faults form?
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Geologic processes
- cools and contracts - decrease in pressure -bend |
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How do you describe fault geometry?
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describes strike and dip and how the strike line is perpendicular to the dip line.
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What is a strike?
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angle between fault surface trace & true north
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What is a slip?
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angle between horizontal plane & dip line
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Difference between a foot wall and hanging wall?
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you can stand on the footwall
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Know the basic types of faults
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Reverse Fault
Thrust Fault Normal Fault |
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How do you identify faults in a field?
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-discontinuous rock layers
-displaced landscape/man made features -fault scarp: step due to dip slip |
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How do you describe fold geometry?
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there is an axis and axis can be plunging or non plunging
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Know fold types, their shapes, and outcrop rock patterns
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Anticline= limbs dip away from hinge
Syncline= limbs dip toward hinge |
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Where can mountain building occur?
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convergent margin orogens
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In what environment did the Andes form?
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along a convergent margin
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what does isostasy mean?
whats its consequences? |
conditions at which buoyancy force= gravitational force, isstatic equilibrium
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why do mountains have roots?
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creates extra buoyancy force
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what is orogenic collapse?
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warmer, softer, flow laterally
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What is a craton?
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consist of crust that has not been affected by orogeny for at least 1 billion years
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CHAPTER 10
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Flash Cards
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