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Ch 15 Earthquakes

Ch 15 Earthquakes. I. Earthquake – the shaking of Earth’s crust caused by a release of energy; vibrations made from rocks breaking. II. Forces Inside the Earth. Elastic Rebound Theory friction prevents movement stress deforms plates

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Ch 15 Earthquakes

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  1. Ch 15 Earthquakes • I. Earthquake – the shaking of Earth’s crust caused by a releaseof energy; vibrations made from rocks breaking

  2. II. Forces Inside theEarth Elastic Rebound Theory • friction prevents movement • stress deforms plates • stress overcomes friction & plates move suddenly because rocks have bent & stretched until they have broken • Results : plates snap back to shape but at new locations; Earthquake

  3. B. Fault • Surface along which rocks break • Rocks move in different directions on either side of a fault http://www.thirteen.org/savageearth/earthquakes/html/sidebar1.html

  4. Focus – place inside the Earth where the quake actually occurs • Epicenter - pt. on Earth’s surface directly above the focus of the quake

  5. E. 3 Forces Rocks Experience • Compression – stress that squeezes compacts • Tension– stress that causes stretching & elongation • Shear – force that causes slippage & the rocks on either side to move past each other

  6. III. Earthquake Information • Seismic waves - energy waves that move outward from the earthquake focus & make the ground quake • 3 Types of SeismicWaves • Primary wave(P-wave) • Secondary wave(S-wave) • Surface wave(L-wave) • Love • Rayleigh

  7. C. Primary waves • Compressional, travel through any material: solid rock, magma, ocean water, & air • Compaction & stretching of rock  • Fastest wave 2 x speed of S waves

  8. D. Secondary wave • Shear, travel through solids, not through liquids or gases

  9. E. Surface waves (Longitudinal waves) - Waves that travel like ripples on a pond across Earth's surface • Travel out from the epicenter • Particles move in an elliptical motion, as well as back & forth • Cause the most destruction • Slowest waves • Two types: Rayleigh & Love waves

  10. Surface Waves

  11. Rayleigh Waves

  12. III. Locating an Earthquake • Seismograph - instrument that detects & records earthquakes • Readings from 3 seismograph stations are needed to locate the epicenter • P-waves travel the fastest • The more time between the P & S waves, the farther away the epicenter is • Damaged area increases as focus depth increases

  13. The difference in arrival times between the P & S waves (from 3 different stations) is used to find the distance to that earthquake.

  14. The difference in arrival times is ___

  15. Richter Scale - the measure of the amount of energy (magnitude) released by a quake, each # is 32 x greater in energy • Moho Discontinuity - boundary between the crust & the mantle • seismic waves speed up because they are passing through a denser region

  16. Moho Discontinuity

  17. Seismology – the study of earthquakes • Seismologist – person who studies earthquakes & seismic waves • Seismograph– instrument used to record seismic waves • Tsunami– ocean waves generated by earthquakes

  18. Cove where Tsunami Hit in 1964

  19. Height of Tsunami Wave

  20. `

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