Earthquakes: Critical Thinking
Directions: Interpret the seismograms below to evaluate this earthquake.
Station A: Fresno, CA
1.
Label the P and S waves in each
seismogram.
2. Lag time is the difference in time
between the P wave arrival and S
wave arrival.
a. Write down the lag time in
seconds for each
seismogram (write on the
seismogram).
Station B: Las Vegas, NV
b.
Which station has the
shortest lag time?
_________________
c. Which station has the
longest lag time?
__________________
3.
Station C: Phoenix, AZ
Amplitude is the height of the
tallest S peak in mm.
a. Write the amplitude (in mm)
next to the tallest S peak for
EACH seismogram.
b. Which station has the
greatest amplitude?
_________________
c. Which station has the
smallest amplitude?
__________________
4. Based on seismic data, which city is
closest to the EPICENTER of the
quake. Defend your answer with a
reason. (sentences)
Figure 2: S-P Lag Time
Figure 3: Nomogram (for Magnitudes)
Directions: Use the lag time from your FRESNO seismogram to determine the distance to the epicenter (lag time graph). Mark this distance on
the nomogram. Then mark the amplitude you measured from the FRESNO seismogram. Connect these two points with a line.
5. How far away from the epicenter is Fresno?
6. What is the magnitude of this quake on the Richter scale?
7. A few months after this quake, a _____ quake occurred in eastern Turkey. Fifty one people died, 100 people
were injured, 5000 were displaced and over 1,000 buildings were heavily damaged or destroyed.
How could this Turkish quake be so much more damaging than the southern California quake you
measured? Think of factors OTHER THAN SIESMIC WAVE SIZE that can influence how
devastating a quake can be.