Finding An Earthquake's Epicenter Lab
Introduction:
To pinpoint the epicenter, analyze the P-wave
and S-wave data recorded at seismic stations.
Analysis:
1. Obtain a map of the western hemisphere from your
teacher and mark the seismic stations listed in the table.
2. For each station, calculate and record the arrival
time differences by subtracting the P-wave
arrival time from the S-wave arrival times.
3. Use the arrival time differences and the travel-time curve to find the distance
between the epicenter and each seismic station. Record the distances.
P-wave S-wave
Arrival Arrival
Time
(PST) (PST)
Newcomb, NY
8:39:02 8:44:02
Idaho Springs, CO 8:35:22 8:37.57
Darwin, CA
8:35:38 8:38:17
4. Draw a circle around each station. Use the distance from the epicenter
as the radius for each circle. Repeat for each seismic station.
5. Identify the epicenter of the earthquake.
Thinking Critically
1. Explain why you need to find the difference in time of arrival
between P-waves and S-waves for each seismic station.
Seismic
Station
So You can
2. Identify sources of error in determining an earthquake's epicenter.
3. Explain why data from more seismic stations
would be useful for finding the epicenter.
can use
Time since earthquake occured (min)
16
15
14
13
12
11
10
9
8
96
Name Caden Homa,
Date \ \\/ 2 Hour
5
4
3
2
1
the time
Arrival
Distance
Time
from
Time Difference Epicenter
(min) (km)
min 3,300
2:39 1,450.
Typical Travel-Time Curves
S-wave curve
P-wave curve
1000 2000 3000 4000 5000
Distance from epicenter (km)