Earthquake Unit: Lesson 2 Recording Earth Quakes and Seismic Waves.
Earthquake Lesson
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Transcript of Earthquake Lesson
Earthquakes
Earth Science 11Ms. McKean
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Objectives
Use the Elastic Rebound Theory to describe how Earthquakes occur.
Identify the epicenter and focus of an Earthquake given a diagram.
Name and describe each of the 4 types of seismic waves including movement, direction, speed, and how they attribute to Earthquake damage.
Describe how Earthquakes are measured and identify which tools are used in this process.
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PART 1What are Earthquakes
What are Earthquakes? The shaking or trembling caused by the
sudden release of potential energy
Usually associated with faulting or breaking loose of locked plates
Continuing adjustment of position results in aftershocks
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Elastic Rebound Theory Explains how energy is
stored in rocks
Forces will cause rocks to bend until a point of deformation
Rocks stay deformed as forces continue until eventually they force breaks
Energy is released from the fault in waves
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The Focus and Epicenter of an Earthquake
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• The point within Earth where faulting begins is the focus
• The point directly above the focus on the surface is the epicenter
Seismic Waves
Response of material to the arrival of energy released by rupture
Two types:
Body waves (P and S)
Surface waves (R and L)
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Body Waves P- waves (Primary Waves)
Fastest moving
Move like sound waves (compression)
Can travel through both solids, liquids & gases
S-waves (Secondary Waves)
Slower than P-waves
Move like a snake
Can only travel through solids (not liquids)
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Body Waves: P and S waves
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Surface Waves: R and L waves
Surface Waves
Rayleigh Waves and Love Waves Travel just below or along the ground’s surface Slower than body waves; rolling and side-to-side
movement Especially damaging to buildings
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Seismic Waves
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Faults
A fault is a fracture in the Earth's crust
3 main fault groups
Faults are classified depending on how they move.
Faults Normal Fault
occur in response to pulling or tension
the overlying block moves down the dip of the fault plane.
Thrust Fault
occur in response to squeezing or compression
the overlying block moves up the dip of the fault plane.
Strike Slip
the blocks move horizontally past one another.
The Normal Fault Strike-Slip Fault
Thrust Fault
Normal Fault
Thrust Fault
Strike Slip Fault
Check your understanding
1. According to the Elastic Rebound Theory, what causes Earthquakes?
2. What is the difference between the focus and the epicentre of an earthquake?
3. What are the 4 types of seismic waves? How do each of them move? (Try and use descriptive examples).
4. What is a fault? Name the 3 types.
PART 2Measuring Earthquakes
Measuring EQs Intensity
The Seismograph The device which records
Earth tremors
The base of the seismograph is anchored to the ground
A pendulum swings when the earth moves
The pen attached to the pendulum records the movement
The Richter Scale
Measures earthquake magnitude
Based on the amplitude of the wave produced on the Seismograph
Each point represents ground vibrations 10 times greater then the point before it
Check your understanding
1. What are the two scales used to measure Earthquakes called? What does each measure specifically?
2. What is the difference in strength between a 4 and a 6 force earthquake on the Richter Scale?
3. Describe how a seismograph works.
PART 3Environmental Impacts
Environmental Impacts
Ground Shaking
Amount depends on three factors:
distance from epicentre the area’s geology the size of the Earthquake
Environmental Impacts
Liquefaction
the vibration of seismic waves causes groundwater to rise to the surface
turns solid ground into a liquid-like material
houses, building will sink into the ground
Environmental Impacts
Tsunamis
a very large sea wave produced by an earthquake
earthquake occurs underwater
earthquake happens, ground moves, water moves to fill in change in ocean floor
wave results
1964 Alaskan Earthquake caused a Tsunami to travel down hit places like Port Alberni and even made it to Hawaii
Check your understanding
1. Name three impacts Earthquakes have on the environment.
2. Which one do you think is the most destructive and why?
3. What does liquifaction do to the ground? Where in BC where this be a very big problem?
4. What is a tsunami?
Quiz
Now that you have finished the presentation its time test your knowledge.
Be sure to read each question carefully.
At the end let me know your score.
Good Luck!
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What is the name of the theory that describes how earthquakes
occur
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A) Focus Theory
B) Elastic Rebound Theory
C) Strike-slip Theory
D) Richter Theory
Where is the focus of an earthquake found?
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A) On the surface of the Earth where the earthquake occursB) In the core of the Earth where the earthquake is generatedC) The location that has the most damage as a result of the earthquake D) The spot within the crust where the earthquate originates
Which of the following are surface waves?
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A) P and S waves
B) S and R waves
C) R and L waves
D) P and L waves
The type of siesmic wave that moves through compressions is
called
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A) a primary wave
B) a secondary wave
C) a rayleigh wave
D) a love wave
Waves that cause the ground to roll and as a result cause lots of
damage are called
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A) Love waves
B) Rayleigh waves
C) Primary waves
D) Secondary waves
How are faults classified?
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A) their size
B) the amount of damage they cause
C) where they occur
D) how they move
Which is NOT a type of fault?
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A) Normal
B) Strike-Slip
C) Thrust
D) Rupture
What does a siesmograph measure?
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A) Intensity
B) Magnitude
C) Amount of Damage
D) Size of possible tsunami
Match the environmental impact on the left to the descriptor on
the right.Column 1 Column 2
A. large wave generated as a result of underwater earthquake
B. causes building to sink
C. amount depends on the distance from the epicenter
B Liquifaction
C Ground Shaking
A Tsunami
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Earthquake Quiz
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