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CH 8 Earthquakes

CH 8 Earthquakes. Produced by the rapid release of elastic energy in rock causing vibrations Elastic Rebound Theory = the rock springs back into it original place Occur at faults and plate boundaries. Vocab. Focus – point within earth where earthquake originates

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CH 8 Earthquakes

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  1. CH 8 Earthquakes • Produced by the rapid release of elastic energy in rock causing vibrations • Elastic Rebound Theory = the rock springs back into it original place • Occur at faults and plate boundaries

  2. Vocab • Focus – point within earth where earthquake originates • Epicenter - point on land surface directly above the focus • Aftershocks – follows the main EQ • Foreshocks – EQs that precede the main earthquake • Seismographs – instrument that records EQ waves • Seismograms – the record made by a seismograph

  3. Earthquake Waves • Primary (P) waves • Body wave, arrives first, fastest, pass through everything, push/pull wave • Secondary (S) waves – • Body wave, arrives second, slower, pass through solids only, sideways/snake wave • Longitudinal (L) waves – • Surface waves, arrive last, liquefy ground, do most damage, up/down wave

  4. Locating an Earthquake • Determined by the difference in arrival times between P and S waves • Know the graph on page 225 • Need at least 3 points to determine the location (triangulation) • EQ zones – circum-Pacific belt and oceanic ridge system

  5. Measuring Earthquakes • Richter scale • Based on size of largest wave • Scale from 1 - 10 • Moment magnitude • More precise • From displacement that occurs along the fault line • Estimates the energy released

  6. Earthquake Destruction • Contributing factors • Intensity of eq • Duration of eq • Foundation of building • Structure/materials of building • Damage prevention • Reinforced concrete • Shock absorbers • Counter weights

  7. Earthquake Dangers • Collapsing structures #1 • Fires #2 • Landslides • Tsunamis • Move fast: 500–950 km/hr (300-600 mph) • Very long wavelengths • Barely noticeable in open ocean

  8. Predicting Earthquakes • Short range prediction are unsuccessful • Long range forecasts are based on the idea that EQs are cyclic. • Land movement • Strain in rocks • Radon gas emissions • Strange animal behavior • Volcanoes • Foreshocks • Seismic gap theory

  9. Earth’s Layers • Earth’s interior consists of 3 major zones (chemical composition) • Crust – thin, rocky outer layer • Oceanic and continental • Mantle – most of earth’s volume • Upper and lower mantle • Core – iron/nickel alloy with extreme pressures • Inner (solid) and outer (liquid)

  10. Earth’s Interior • Lithosphere • Solid and rigid • The crust and upper mantle • Asthenosphere • Softer and flows • Rest of the mantle • Moho Discontinuity • Boundary that separates the crust from mantle • Shadow zone • Know differences between oceanic and continental crust

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