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Locating an Epicenter

Locating an Epicenter. Fastest. P-Waves - S-Waves - L-Waves - (surface waves). Used to locate an earthquake. Slower. Slowest. Different waves, different speeds. Measuring Seismic Waves. 1. Laser Geodimeter. 2. Creep Meter. 3. Seismograph. 3 Instruments:. 1. Laser Geodimeter.

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Locating an Epicenter

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  1. Locating an Epicenter Fastest P-Waves - S-Waves - L-Waves - (surface waves) Used to locate an earthquake Slower Slowest Different waves, different speeds

  2. Measuring Seismic Waves 1. Laser Geodimeter 2. Creep Meter 3. Seismograph 3 Instruments:

  3. 1. Laser Geodimeter 1. Laser Geodimeter A measuring device using laser light to detect movement of the earth’s crust

  4. 2. Creep meter - A device used to detect subtle movement through the use of a wire

  5. 3. Seismograph- An instrument used to register earthquake waves and record the time that they arrive

  6. a. Seismogram- The lines traced on the recording tape during a quake Height determines strength

  7. b. Seismologist- The person who studies earthquakes BENO GUTENBERG was the foremost observational seismologist of the twentieth century. http://newton.nap.edu/html/biomems/bgutenberg.html

  8. Seismograph Stations Quake Local <100km Regional 100-1400km Teleseismic > 1400km Triangulate to find epicenter -use wave speeds to locate epicenters

  9. Basic Structure of the Earth

  10. Basic Structure of the Earth Crust – outer layer -between 5km and 60km thick -lots of Si & Al little Fe & Mg -less dense than mantle

  11. Basic Structure of the Earth Mantle – Largest layer -lots of Si, O, Mg, & Fe -Upper and Lower mantle -Asthenosphere –weak rock that can flow slowly

  12. Basic Structure of the Earth Outer Core – Liquid – Mostly Fe

  13. Basic Structure of the Earth Inner Core – Solid – Mostly Fe

  14. Mapping Earth’s Internal Structure The speeds and paths of seismic waves change as they move through different materials As DEPTH Increases, DENSITY Increases

  15. Shadow Zones- Areas of the earth that DON’T receive seismic waves

  16. P-waves-slowed and bent by liquid outer core -speed up in the inner core S-waves- cannot travel through liquid -travel in mantle only

  17. Layer Boundaries Mohorovicic Discontinuity (Moho)-Boundary between the crust and upper mantle

  18. People and Earthquakes • Provide info. About the Earth’s interior • -Cause BILLIONS of $ in damage • (lost lives/destruction) Earthquake Activity

  19. Studying Earthquakes • Use seismographs seismograms -Seismologists

  20. Measuring Earthquake Magnitude Measure of the energy released during an earthquake (shown on a seismogram) Magnitude-

  21. A measurement of the MAGNITUDE of an earthquake by calculating the seismic ENERGY released. (based on the height of the lines of the seismogram) Richter Scale- -No upper limit (9.5) -Most quakes are too low to be felt 55,000 3.0 - 4.9 1000’s every day < 3.0

  22. Describing Earthquake Intensity Mercalli Scale- A scale for measuring the seismic intensity of an earthquake by rating THE EFFECTS (amount of damage) at different sites

  23. Damage depends on: • Strength of quake • Nature of surface material • Design of structures • Distance from epicenter

  24. Occurs when wet soil acts more like a liquid during an earthquake • May cause buildings to sink or collapse Liquefaction-

  25. Seismic Seawave • Begins over the earthquake’s focus • Can be highly destructive • Can reach 30 meters high !! Tsunamis- (Pacific Tsunami Warning Center, Hilo Hawaii)

  26. Earthquake Safety Can’t predict but… Knowing where quakes are likely to happen helps us to prepare

  27. Quake Resistant Structures Most loss of life is due to crumbling structures • Reinforced walls with steal bars • Flexible foundation supports • (absorb shock)

  28. Before a Quake -Move heavy objects to lower shelves -Learn how to turn off gas/water/ electric - Secure hot water heater and other major appliances

  29. During a Quake Indoors- Move away from glass and falling objects -get under a sturdy door frame or table / desk

  30. During a Quake Outdoors- Stay away from power lines, buildings, chimneys -get out in the open

  31. After a Quake -Check gas/water/electricity for damage -shut off valves -Leave building, call authorities -Be careful, things could still fall

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