1. Interpreting Seismograms

2. Wave Types P waves (compression waves) Fastest
S waves (transverse waves)
Mid Speed
Surface waves
Slowest, may not reach far from epicenter

3. Review Do we feel every earthquake that happens in the world?
Do mechanical waves generated by earthquakes reach our location?

4. How do geologists know that a major earthquake occurred on the other side of the world?

5. Detecting earthquakes

6. Seismometer

7. Recording Earthquake events

8. Seismograph

9. Seismogragh reading

11. Measuring an earthquake at a distance
Seismographs-
sensitive machines that record the different types of seismic waves generated by an earthquake
Measuring the difference between the arrival times of different types of waves indicates how far away the epicenter is from the seismograph machine

12. What information can be gathered from a seismograph reading?

13. Arrival times for different waves

14. Determine distance to epicenter
The difference in time between arrival of the P and S wave can be used to determine distance between epicenter and seismograph
The bigger the difference, the greater the distance

17. Seismograph reading

18. Why can’t the difference between waves give the distance but not direction to epicenter?

19. What is needed to determine the epicenter of an earthquake?

20. Seismograph readings from instruments in 3 different locations

21. Finding the epicenter

22. Other uses for Seismic waves
Used to gather data on the interior structure of the earth
S-waves do not go through __________ material.

23. A cross sectional map using info from seismic waves

24. Locations of different earthquakes over the last 20 years
Usgs program
Show large quakes
Show shallow quakes
Look for patterns

25. World Earthquakes

26. Volcanoes and Earthquakes

27. Ring of Fire Location Significance? Atlantic ocean Mediteraanen
East Africa