1 / 22

Warm Up 10/31

This text provides an overview of earthquakes, including the energy release during earthquakes, measurement methods, and the global distribution of earthquakes. It also covers seismographs, seismograms, earthquake waves, locating an earthquake's epicenter, and the Richter Scale and Modified Mercalli Scale.

jhopson
Download Presentation

Warm Up 10/31

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. Warm Up 10/31 • When an earthquake occurs, energy radiates in all directions from its source, which is called the ____. a. fault c. seismic center b. epicenter d. focus • The hypothesis that explains the release of energy during an earthquake is called the ____. a. moment magnitude hypothesis c. Richter hypothesis b. elastic rebound hypothesis d. vibration hypothesis • Most earthquakes are produced by the rapid release of which kind of energy stored in rock subjected to great forces? a. thermal c. chemical b. elastic d. mechanical Answers: 1) d. 2) b. 3) b.

  2. Measuring Earthquakes Chapter 8, Section 2

  3. Seismographs • Seismographs – instruments that record earthquake waves • When waves from an earthquake come into contact with a seismograph, a weight suspended from a support will remain motionless as Earth moves (providing a reference point) and can draw a diagram showing Earth’s motion • Seismograms – the electronically recorded ground motion from a seismograph

  4. Seismographs

  5. Seismograms

  6. Earthquake Waves • Surface Waves – seismic waves that travel along Earth’s surface, most destructive seismic waves • Surface waves travel along the ground and cause the ground and anything resting upon it to move • P waves – push-pull waves; they push (compress) and pull (expand) rocks in the direction the waves travel • S waves – shake the particles at right angles to their direction of travel • Gases and liquids do not transmit s waves, but do transmit p waves • A seismogram shows all three types of waves: the p waves arrive first, then the s waves, followed by the surface waves last • The waves arrive at different times because they travel at different speeds

  7. Surface Waves

  8. P Waves

  9. S Waves

  10. Concept Check • Which seismic wave travels fastest? • P waves

  11. Locating an Earthquake • We can determine the distance to an epicenter by finding the difference between the arrival of p waves and s waves , then looking at a travel-time graph we can determine how far away the epicenter is • Travel-time graphs from three or more seismographs can be used to find the exact location of an earthquake epicenter • About 95% of earthquakes occur in a few narrow zones, and most of these occur around the Pacific Ocean

  12. Travel-Time Graph

  13. Finding an Epicenter

  14. Global Distribution of Earthquakes

  15. Concept Check • Where do most earthquakes occur? • Along the edge of the Pacific Ocean

  16. Measuring Earthquakes • Historically, scientists have used two different types of measurements to describe the size of an earthquake – intensity and magnitude • Richter Scale – outdated scale for measuring the magnitude of earthquakes, uses amplitude of the largest seismic wave and uses a logarithmic scale (ten times increase for every increase of 1 on the scale) • Moment Magnitude – derived from the amount of displacement that occurs along a fault zone (surface area of fault) x (avg. displacement along fault) x (rigidity of rock) • Moment magnitude is the most widely used measurement for earthquakes because it is the only magnitude scale that estimates the energy released by earthquakes

  17. Moment Magnitude

  18. Concept Check • Which scale is the most widely used for measuring an earthquake’s magnitude? • Moment Magnitude

  19. Modified Mercalli Scale • Modified Mercalli Scale – rates an earthquake’s intensity in terms of the earthquake’s effects at different locations • It has 12 steps, expressed as roman numerals • An earthquake that can barely be felt is rated as a I • An earthquake that causes near total damage is rated as a XII • The same earthquake can be given different ratings at different locations

  20. Modified Mercalli Scale

  21. Some Notable Earthquakes

  22. Assignment • Read Chapter 8, Section 2 (pg. 222-228) • Do 8.2 Assessment #1-6 (pg. 228)

More Related