1. Do First Which type of lava does not trap gases?
Which type of volcano is most explosive?

2. Agenda
Finding the Epicenter of an Earthquake Notes
Test Study Guide

3. Finding the Epicenter of the Earthquake

4. Steps to Finding the Epicenter
Collect Data
Calculate Lag Time
Determine Distance to the Epicenter
Triangulate to Find the Epicenter

5. 1. Collect Data Data must be collected from 3 seismic stations
The data is collected by a seismograph and recorded on a seismogram

6. 2. Calculate Lag Time Lag time = arrival of s-wave – arrival of p-wave
P wave always arrives first
Station 1 Data:
Lag time = 2:26 – 2:22 = 4 minutes

7. Practice
Station 2 Data: Lag Time:
Station 3 Data: Lag Time:

8. Which station is closest to the epicenter?
Station 1: Lag Time = 4 minutes
Station 2: Lag Time = 2 minutes
Station 3: Lag Time = 7 minutes
Which station is the farthest from the epicenter?

9. 3. Distance to the Epicenter
Use the graph to determine the distance from the seismic station to the earthquake
Match the lag time to the space between P and S wave to determine the distance

10. Example
2100 km
Station 1
Lag Time = 4 minutes
1310 miles

11. Practice Station 2 Lag Time = 2 minutes Distance to epicenter
Miles: ________ Km:_________
Station 3
Lag Time = 7 minutes

12. Practice Station 2 Lag Time = 2 minutes Distance to epicenter
Miles: 500 mi Km: 800 km
Station 3
Lag Time = 7 minutes
Distance to epicenter
Miles: 3000 mi Km: 4800 km

13. Reading the Graph
If the earthquake is 1500 miles when will the P – wave arrive?
If the earthquake is 2000 miles away, what was the lag time?
If the earthquake is kilometers away, when did the S-wave arrive?
If the P-wave arrived in 5 minutes, when did the S-wave arrive?

14. 4. Triangulate to Find the Epicenter
Draw distance circles at each seismic station to triangulate the location of the Earthquake
Where all circles intersect is the location of the epicenter
1310 miles
500 miles
3000 miles

15. Where is the epicenter?
What city did the Earthquake occur in?

16. Study Guide Last page of homework/classwork packet
DO NOT HAVE TO DEFINE VOCABULARY
But I will give you 1 point – 15 words defined

17. DYL
1. Which wave is the first wave to arrive to area after an earthquake has occurred?
2. Which wave is most destructive type of wave (body or surface waves)?