1 / 22

GEOL3025, Section 096 Lecture #19 18 October 2007

GEOL3025, Section 096 Lecture #19 18 October 2007. Dr. Lysa Chizmadia. Measuring Earthquake Sizes. Intensity Scale Mercalli Intensity Scale Based on destruction of buildings Magnitude Scales Richter Magnitude (logarithmic)

hollye
Download Presentation

GEOL3025, Section 096 Lecture #19 18 October 2007

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. GEOL3025, Section 096Lecture #1918 October 2007 Dr. Lysa Chizmadia

  2. Measuring Earthquake Sizes • Intensity Scale • Mercalli Intensity Scale • Based on destruction of buildings • Magnitude Scales • Richter Magnitude (logarithmic) • Based on the Amplitude of the largest seismic wave recorded on seismogram

  3. Mercalli Intensity Scale

  4. Richter Magnitude Scale

  5. Earthquake Destruction • Seismic Vibrations • Tsunami • Landslides & Ground Subsidence • Fire

  6. Formation of Tsunamis

  7. Global Distribution of Earthquakes

  8. Evidence for Plate Tectonics

  9. Chapter 12: Earth’s Interior

  10. Velocity of seismic waves depends on density (ρ) & elasticity of material Velocity of waves increases with depth b/c pressure (P) makes rocks more elastic Refraction of waves occurs when they pass from one material to another P waves travel through both liquids & solids S waves travel only through solids P waves travel faster than S waves in all materials Propagation of Seismic Waves

  11. P waves Compressional First to arrive (primary) Travel through both liquids & solids P waves

  12. S waves • S waves • Shear waves • Second to arrive • Travel through solids only

  13. Through Uniform Solid Constant velocity with depth Through Solid of Increasing P Increasing velocity with depth Propagation of Waves

  14. Wave Propagation Through Earth • Because Earth has differentiated, waves travel at different speeds through the different layers

  15. Layers Defined by Composition • Crust: • 3-70 km thick outer skin • Mantle: • 70-2900 km solid silicate-rich shell • Core: • Fe-rich sphere with 3486 km radius

  16. Lithosphere: 3-250 km thick crust & uppermost mantle Cold and rigid Asthenosphere: 250-660 km lower upper mantle Warm and soft Mesosphere: (lower mantle) 660-2900 km lower mantle More rigid than asthenosphere due to increased P Inner Core: 2270 km thick Liquid b/c s-waves don’t penetrate Convection produces Earth’s magnetic field Outer Core: Fe-Ni metallic sphere with radius of 3486 km Solid because of increased P Layers Defined by Physical Properties (Seismic Waves)

  17. Earth’s Layers

  18. Earth’s Major Boundaries • The Mohorovičič discontinuity (Moho) • Divides Crust from Mantle • Seismic velocities higher in Mantle so deeper waves arrive earlier • Core-Mantle Boundary • P-wave shadow zone 105°-140° • Due to high refraction of waves • S-waves do not penetrate at all • Inner-Outer Core • P-waves reflected off surface of solid inner Core • P-waves faster in inner Core than in outer Core

  19. The Moho

  20. Core-Mantle Boundary

  21. Core-Mantle Boundary

  22. Discovery of Inner Core

More Related