1. Focus Question: HOW CAN WE LOCATE THE EPICENTER OF AN EARTHQUAKE?

2. Is caused by an an earthquake under the ocean
TSUNAMI
Is caused by an an earthquake under the ocean

4. Formation of a tsunami

5. Tsunamis

6. Seismographs
Allow us to measure Seismic Waves and study earthquakes

7. Both travel faster as the pressure or density increases
They travel faster (and take less time)
They travel slower (and take more time)
Both travel faster as the pressure or density increases
They can travel through any type of material
They can travel only through solids
They cause a vibration perpendicular to the direction of movement of the waves
They cause a vibration parallel to the direction of movement of the waves

8. The velocity for both P and S-waves increases
The velocity for both P and S-waves decreases

9. Seismic Waves Primary/compressional waves (P): travel faster
through solids, liquids, gases, and plasma
arrive first
Secondary/Sheer/(S):
travel slower
through solids only
arrive second
Surface waves: most destruction

10. The farther away a seismograph is from the epicenter, the longer the difference between the arrivals of the P- and S- waves

11. The smaller the difference in arrival time between P & S;
Farthest
Closest
The smaller the difference in arrival time between P & S;
The closer the station to the epicenter

13. 20 Seconds
200 Km

15. Question 1
Classwork
P waves 5 min
S waves 9 min
Difference 4 min

16. Question 2
4,200 Km

17. Question 3
4, 800 Km

18. Question 4
9 min 40 sec

19. Question 5
S waves 12:40
P waves 7:00
Diff 5 min 40 sec

20. One seismic station report allow us to find the distance to the epicenter
As the distance from the epicenter increases, the difference in arrival time increases
The average velocity: distance ÷ time

21. How is an Earthquake’s Epicenter Located?

22. How is an Earthquake’s Epicenter Located?
Three seismograph stations allow us to locate the epicenter of an earthquake
A circle represents each station
The intersection of the 3 circles locates the epicenter

23. Triangulation of 3 stations to locate earthquake epicenter

24. Earthquake time & Arrival Time (P & S Waves)
Arrival time: Earthquake origin time + P/S travel time
Earthquake Origen time: P/S arrival time – P/S travel time

26. Locating an Earthquake

27. Time-Travel Curve

28. Locating an Earthquake Epicenter
Triangulate means to use three positions to determine an exact location.

29. Locating Earthquakes