Physical Geology
EXAM: Earthquakes
Name _____________________
Date ____________
© E. Fermann, 2007
Part 1: Multiple Choice.
Answer the following multiple choice question by selecting the most appropriate answer
or answers from the choices. [1 point each]
1. The location of the source of an
earthquake is referred to as its
__________.
a. locus
b. epicenter
c. focus
d. rebound
e. displacement
5. The Mercalli intensity scale ranks
earthquakes according to
__________.
a. magnitude
b. damage caused by an earthquake
c. seismic wave amplitude
d. depth below the surface
e. none of the above
2. Following a major earthquake, a
series of smaller earthquakes, called
__________, often occurs.
a. tremors
b. seismograms
c. elastic rebounds
d. foreshocks
e. aftershocks
6. The damage caused to a building by
an earthquake depends on the
__________.
a. duration of the vibrations
b. intensity of the waves
c. material on which the building
rests
d. all of the above
e. none of the above
3. Of the seismic waves produced by an
earthquake, which type travels
fastest?
a. surface waves
b. long waves
c. P-waves
d. Richter waves
e. S-waves
4. Most earthquakes occur
__________.
a. in Russia
b. in the central United States
c. around the outer edge of the
Pacific Ocean
d. in the North Atlantic
e. beneath Earth's mantle
7. Large seismic sea waves produced
by earthquakes are called
__________.
a. tsunamis
b. liquefactions
c. subsidences
d. seiches
e. swells
8. Most of the world's largest
earthquakes occur as a result of
which type of stress?
a. compressional
b. shear
c. tensional
Score: ____/40
 Examine the following 3-component seismic record.
o (remember…up = east, north, and up)
9. What was the first motion for each of the three component seismograms? [3pts]
E-W
N-S
UD
_______
_______
_______
10. In which quadrant did this earthquake take place
(circle one)? [1 pt]
NW
NE
11. Describe (in complete thoughts) how you know
which quadrant the EQ occurred in. [3 pts]
SW
SE
 Below is an image of a seismic record from the 1996 Northridge (California)
Earthquake. These waves were recorded at the station BKS. Notice that the times on
the left are in hh:mm:ss and that seconds (3 second intervals) run across the top of
the image.
12. Using a pen or pencil, label the P and S wave arrivals at this station in the record
above. [2 pts]
Record the times of arrival below.
P Arrival: ___________________ [1 pt]
S Arrival: ___________________ [1 pt]
13. Based on your measurements from question 12 and the simple formula for
determining the distance to an earthquake to calculate how far away the earthquake
was from this seismic station. [2pts]
distance (km) = (S-P time in seconds) x 8
14. Use a compass to draw the possible location for this earthquake on the map on the
following page. The total length of the scale at the top of the page is 200 km. [2 pts]
15. How could a group of seismologists differentiate between a seismic record was the
result of an earthquake and that of a nuclear test? Be specific. [3 pts]
16. A. If a seismometer was located at the surface of the earth directly above the focus of
the earthquake (that is, at the epicenter), what would be the first evidence at the
seismomter that an earthquake had occurred? [2 pts]
16. B. How soon after the quake occurred would that evidence be observed? (hint: there
may NOT be a definite answer to this question) [2 pts]
17. What did Hugo Benioff discover about the relationship between earthquakes and the
distance from a subduction trench? Draw a picture below to help your explanation.
Why does this occur? [3 pts]
18. Why did Hugo observe that “benioff-type” earthquakes do not occur below 670 km?
[2 pts]
 Examine the seismic records on the following page. These were both recorded in
Alaska as a result of a major (magnitude 8.4) earthquake in 1964…we’ve seen
this record before…
 Three aftershocks are identified as A, B, and C…so pay attention to those.
19. In general, what is the relationship between the distance from the epicenter and the
differences in P and S wave arrival times? [2 pts]
20. How does this help you intrepret the seismic events labeled A, B, and C? [3 pts]