1. 8.2 Measuring Earthquakes  A) Seismographs - instruments that record earthquake waves.  B) Seismograms electronically recorded ground motion made by seismographs. I. Instruments

2. Seismograph

3. Seismogram

4. II. Earthquake Waves 8.2 Measuring Earthquakes  A) Body Waves 1) P waves - Have the greatest velocity of all -Are push-pull waves that push (compress) and pull (expand) - Travel through solids, liquids, and gases

5. Earthquake Waves 8.2 Measuring Earthquakes S waves - Slower velocity than P waves - Travel only through solids

6. 8.2 Measuring Earthquakes  Surface waves seismic waves, travel along Earth’s outer layer.

7. Seismic Waves

8. Locating an Earthquake 8.2 Measuring Earthquakes  Earthquake Distance Travel-time graphs from 3 or more seismographs can be used to find the exact location of an earthquake epicenter. The epicenter is located using the difference in the arrival times between P and S wave  Earthquake Direction

9. Measuring Earthquakes 8.2 Measuring Earthquakes Richter Scale  Richter Scale Based on the amplitude of the largest seismic wave. Increases 32 times each increase

10. Measuring Earthquakes 8.2 Measuring Earthquakes  Moment Magnitude Moment magnitude is the most widely used - estimates the energy released by earthquakes.

11. Earthquake Magnitudes

12. - The majority of all earthquakes that occur on Earth are found at or near plate boundaries. 8.2 Earthquake locations

13. Some Notable Earthquakes