Download Finding an earthquake epicenter Geologists who study earthquakes

Finding an earthquake epicenter
Geologists who study earthquakes are called seismologist. If you were a seismologist, you would receive data from
seismographs all over the world. Each recording stations I constantly collecting data on all tectonic disturbances in the
crust. Within minutes of an earthquake, seismographs would record the arrival times of the P-waves and S-waves. Since
P-waves travel faster than s-waves, if there is a longer period of time from when the P-waves arrive to when the S-waves
arrive, you know that the epicenter is located farther from the recording station. You use the P and S wave data from at
least three recording stations to pinpoint the location of an earthquake epicenter. If there is information from only one
station, the epicenter of the earthquake could at any point on that circle. If there is information from two stations, the
circles intersect at two points, so there are two possible epicenters. With three stations, the circles intercept at only one
point, which must be the epicenter.
Procedure:
1.
2.
3.
4.
5.
Look at the chart indicating the difference in arrival
times from P and S waves from the three recording
stations.
Use your time travel curve to determine the distance to
the epicenter from each city.
Using the scale on your map, and your compass, draw a
circle with a appropriately sized radius around the city.
This represents the possible location of the epicenter in
all directions.
After circles are drawn, the point where they intersect
represents the location of the epicenter.
Describe the location of each epicenter using the
closest city.
Earthquake # 1
City
Difference
in arrival
time of P&
S Waves
Earthquake # 2
Distance to City
Difference
epicenter
in arrival
determined
time of P
from travel
and S
time curve
Waves
Km
Denver
2:20
Km New York
2:00
km
Miami
3:00
Earthquake # 3
Distance to City
Difference
epicenter
in arrival
determined
time of P
from travel
and S
time curve
Waves
Km Salt Lake
3:25
Km
Miami
3:00
km
Chicago
2:30
Distance to
epicenter
determined
from travel
time curve
Km
Km
km
Seattle
2:00
Denver
2:30
Houston
4:00
Questions:
1. What are the locations of the earthquakes? Earthquake #1 - ______________________Earthquake #2 ______________________Earthquake #3 - ______________________
2. Why do you need at least three seismic recording stations?
3. Which earthquake wave travels faster? ________________________________
4. What happens to the difference in arrival times between S and P waves as you get further from the epicenter?
5. If you notice there are many epicenters located in one area of the earth, what does that tell you about that area?
What type of plate boundary would be present?