1. Quiz/Review Get out a small piece of paper and put your name on it.
When the bell rings, the quiz will begin.

2. Question 1
Where do most earthquakes occur?

3. Question 2
Why have so many more people died from earthquakes in the recent years compared to 200 years ago?

4. Question 3
Where is the epicenter of an earthquake?

5. Answers Plate boundaries More population, cities concentrate people
Epicenter is directly above the focus and on the surface of the earth.

6. How to find an Earthquake?!

7. How do we locate exactly where an earthquake occurred?
Using seismic waves collected around the world.
Identifying where the energy is the greatest.
Using charts.
Computers do much of the work now, but humans have to double check and confirm.

9. Steps (write this down)
Find P wave arrival
Find S wave arrival
Find Difference (S-P)
Subtract
Ref Table
Use number from step 2
Go to map and draw circle to scale at distance
Repeat at least two more times

10. Reference Table Which wave is faster?
What happens as you get further away?
Each line = __________
Each line = _________

11. Step 1: P and S wave arrival
P-wave arrival time = ???
First big blip
S-wave arrival time = ???
Second big blip
P = 4 minutes
S = 8 minutes

12. Step 2: Find Interval P = 4 minutes S = 8 minutes hr : min : sec
S-wave 00:08:00
P-wave -00:04:00
00:04:00 minutes
Take the 4 minutes and open your ESRT to pg 11.
ALWAYS use
hr : min : sec
Format!

13. Step 3: Ref Table Find 4 minutes HERE (RED line)
1. Then, count the boxes or draw a line on scrap.
2. Then, slide the scrap or count the difference in between S & P waves
3. Read off distance on x axis
2800 km

14. Be carful do NOT over turn the screw!
Safety compass Safe? 
Be carful do NOT over turn the screw!
Set center point to 0.
Move arrow to distance.
Put your finger on circle and pen in arrow.
Distance slider
1000
2000
3000
Safer !
Center circle

15. Step 4: Map It!
1000
2000
3000

16. Step 5: Do it again Find P wave arrival Find Difference (S-P)
~S wave arrival
Find Difference (S-P)
Ref Table
~Use number from step 2
Go to map and draw circle to scale at distance

17. Now what?? Where is the EQ?
1000
2000
3000

18. Do it again Find P wave arrival Find Difference (S-P) Ref Table
~S wave arrival
Find Difference (S-P)
Ref Table
~Use number from step 2
Go to map and draw circle to scale at distance

19. 1000
2000
3000
EQ is Here

20. Let’s Review Step 1: Step 2: Step 3: Step : 4: Steps 5:
Find the arrival times
Step 2:
Subtract S-P wave times (S-P interval)
Look up on ESRT 11 the distance.
Step 3:
Find the S-P interval on the Y-axis and then find that in between the P & S wave lines.
Step : 4:
Once you have 1 distance draw circle.
Steps 5:
Repeat at least 2 more times!

21. P-Wave travel time
This is the time it takes for the P-wave to get to the recording station.
It’s simple to find!
Use the epicenter distance you already found.
Go to that distance on your ESRT and follow a line up to the P-wave line.
Follow to the left and read off the time!

22. Let’s try Subtract: 12:00:00 11:34:30 01:21:10
12:00: :34: :21:10
-11:55: :30: :18:18
Station
(City)
Arrival
P-wave
S-wave
S-P time
+/-
(00:00:30)
Distance
+/- (200km)
P-wave travel time A
11:55:30
12:00:00 B
11:30:50
11:34:30 C
01:18:18
01:21:10

24. Locating an epicenter video