Earthquakes and Seismic Waves 6 th Grade: Section 2 Chapter 2.
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Transcript of Earthquakes and Seismic Waves 6 th Grade: Section 2 Chapter 2.
![Page 1: Earthquakes and Seismic Waves 6 th Grade: Section 2 Chapter 2.](https://reader035.fdocuments.us/reader035/viewer/2022072006/56649d215503460f949f707c/html5/thumbnails/1.jpg)
Earthquakes and Seismic Waves
6th Grade: Section 2 Chapter 2
![Page 2: Earthquakes and Seismic Waves 6 th Grade: Section 2 Chapter 2.](https://reader035.fdocuments.us/reader035/viewer/2022072006/56649d215503460f949f707c/html5/thumbnails/2.jpg)
Review: Forces in the Earth’s Crust
• Shearing is the movement that happens to the crust along a Transform Boundary
• Tension is the movement that happens to the crust along a Divergent Boundary
• Compression is the movement that happens to the crust along a Convergent Boundary
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What are the 3 types of faults we have studied?
• Normal Fault:– occurs when plates diverge– results from tension – The hanging wall slips below the footwall
• Reverse Fault:– Occurs when plates converge– Results from compression – The hanging wall moves up above the footwall
• Strike-slip Fault:– Occurs when plates slip past each other – Results from shearing – Sideways motion, not up and down
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Where do Earthquakes come from?
• PLATE TECTONICS!
• When plates move and create faults, the force exerted on the crust (compression, tension, or shearing) creates Earthquakes
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What is the definition of an Earthquake?
• The shaking and trembling that results from tectonic plates shifting, causing rocks to break along fault lines and releasing energy throughout the earth’s interior.
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What are the components of an Earthquake?
• Focus: the area within the Earth’s lithosphere where the rock breaks, triggering the Earthquake
• Epicenter: the point on the Earth’s surface directly above the focus
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Earthquake components: Seismic Waves
• Seismic Waves: the vibrations traveling through the Earth that carry the energy released during an Earthquake
– 3 types of Seismic Waves: • P waves (primary)• S waves (secondary)• Surface waves
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Seismic Waves
• P waves: seismic waves that compress and expand like an accordion
• S waves: seismic waves that vibrate from side to side as well as up and down
• Surface waves: when p and s waves reach the epicenter, and move across the surface of the Earth in the motion of waves like the ocean
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Waves in the Earth’s Interior:Slinky Demonstration:http://www.youtube.com/watch?v=KZaI4MEWdc4
• P-wave motion: – They move the fastest and can move through
solids and liquids– Can damage buildings when they reach the
surface
• S-wave motion: – Move more slowly than P waves – Cannot move through liquids
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Common Questions after Earthquakes:
• “How big was the quake?”
• “Where was the earthquake centered?”
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Measuring Earthquakes
• 1) Mercalli scale
• 2) Richter scale
• 3) Moment Magnitude Scale
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Measuring Earthquakes
• Mercalli Scale: 12 step rating based on how much damage the earthquake causes on the surface of the Earth– The same earthquake can have different ratings
at different locations
--uses Roman numerals: I, II, III, IV, V, VI, VII, VIII, IX, X, XI, XII
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Mercalli Scale:
• I-III: People notice vibrations like those from a passing truck
• IV-VI: Slight damage. People run outdoors. • VII-IX: Moderate to heavy damage. Buildings
jolted off foundations or destroyed• X-XII: Great destruction. Cracks appear in the
ground. Waves seen on the surface.
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Measuring Earthquakes
• The Richter Scale: a measurement of an earthquake’s magnitude (the size of the waves)
• Scientists assign a magnitude by measuring an earthquake’s seismic waves
• Scientists use a SEISMOGRAPH to measure the seismic waves on a Richter Scale
• Provides accurate measurements for small, nearby earthquakes. But does not work well for large or distant earthquakes
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Measuring Earthquakes
• Moment Magnitude Scale: – Estimates the total energy released by an
Earthquake
– Measure the magnitude of the seismic waves, the strength of the rocks that broke, the distance that the fault slipped
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Canterbury, Sept.4, 2010 magnitude= 7.1
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Myanmar, March 25th 2011magnitude 6.8
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Virginia August 23 2011magnitude 5.8
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Great Chilean Earthquake: 1960, magnitude= 9.5
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Magnitude: tells how much energy was released by the earthquake
• Each one point increase in magnitude represents a release of 32 times as much energy
• Earthquake with a magnitude of 5 releases 32 times as much energy as an earthquake with a magnitude of 4