Download - Earthquake Waves
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EarthquakeWaves
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Focus: point in Earth where energy is released
Epicenter: point on surface above earthquake
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Richter Scale measures magnitude of an earthquake- a magnitude 7 has 10x more ground movement than magnitude 6
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Types of Seismic Waves– Primary waves (p waves)
• Fastest waves• Can travel through any material
– Secondary waves (s waves)• Slower than P waves• Can travel only through solids (no liquids)
– Surface waves (l waves)• Energy waves that reach the Earth’s surface• Most damaging earthquake waves
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Speed up when going through Denser material. These are the fastest waves!
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These waves can only travel through solids. Slower than P-waves.
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P waves S waves
Primary Waves Secondary Waves
Travel faster, and at seismic stations first. Travel slower, and arrive at seismic stations second.
Push-pull, or compression waves. Side-to-side, or shear waves.
Travel through solids, liquids, and gases. Travel only through solids.
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Surface waves • L – Waves• Slowest waves • Most destructive!!!
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Earthquake Damage & Loss of Life Depend On:
• Earthquake magnitude• Duration of ground movement
• Depth of focus
• Type of ground particles
• Building design
• Fire / Landslides / Tsunami
• Emergency and medical services Video on Haiti earthquake magnitude 7.0
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Tsunami
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Seismic risk in U.S.
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Faults in North Carolina
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Let’s Review…How do scientists know what the Earth’s interior is made of?
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Moho Boundary• Discovered in 1909 by Andriji Mohorovicic.• Boundary between Crust & Mantle. • Change in speed of seismic waves!!!
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Remember, Earth is composed of layers
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Liquid Outer Core: Iron-Nickel Liquid• S waves stop at a depth of 2900 kilometers since
they cannot travel through liquids• P waves also slow down because less dense
– Composed of liquid iron and nickel.
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Inner Core: Solid Iron-Nickel Metal– P waves speed up
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Seismograph – Device used to Measure Earthquake Waves
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Seismogram – the record of the ground shaking made by a seismograph
• Determines:–Speed of Waves–Distance to earthquake’s epicenter
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Seismogram• Average time travel of P &
S waves. • Find time between P & S
wave. • Go vertically to find the
distance from the epicenter.
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Example to Do Together:
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To find the Epicenter you need at least 3 stations distances! (triangulation)
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Locating the epicenter of an earthquake
• Use distances of earthquake from three observatories.
•Use a compass
• Intersection of circles determines epicenter
San Francisco
Denver
Tucson