Earthquakes and Earth’s Interior - The Changing Earth: Exploring Geology and Evolution - page 219

Review Questions

1. The minimum number of seismographs needed to
determine an earthquake's epicenter is
a. _____ 1;
b. _____ 2;
c. _____ 3;
d. _____ 4;
e. _____ 5.
2. Most of Earth's internal heat is generated by
a. _____ moving plates;
b. _____ volcanism;
c. _____ earthquakes;
d. _____ radioactive decay;
e. _____ meteorite impacts.
3. The majority of all earthquakes take place in the
a. _____ spreading-ridge zone;
b. _____ Mediterranean-Asiatic belt;
c. _____ rifts in continental interiors;
d. _____ circum-Pacifi c belt;
e. _____ Appalachian fault zone.
4. A tsunami is a(n)
a. _____ part of a fault with a seismic gap;
b. _____ precursor to an earthquake;
c. _____ seismic sea wave;
d. _____ particularly large and destructive earthquake;
e. _____ earthquake with a focal depth exceeding
300 km.
5. The seismic discontinuity at the base of the crust is
known as the
a. _____ transition zone;
b. _____ magnetic refl ection point;
c. _____ low-velocity zone;
d. _____ Moho;
e. _____ high-velocity zone.
6. The total amount of energy released by an earthquake
at its source is its
a. _____ intensity;
b. _____ dilatancy;
c. _____ seismicity;
d. _____ magnitude;
e. _____ liquefaction.
7. An epicenter is
a. _____ the location where rupture begins;
b. _____ the point on the Earth's surface vertically
above the focus;
c. _____ the same as the hypocenter;

d. _____ the location where energy is released;
e. _____ none of these.
8. How much more energy is released by a magnitude-7
earthquake than a magnitude-3 earthquake?
a. _____ 4;
b. _____ 810,000;
c. _____ 27,000;
d. _____ 90;
e. _____ 2,500,000.
9. The geothermal gradient is Earth's
a. _____ capacity to refl ect and refract seismic waves;
b. _____ most destructive aspect of earthquakes;
c. _____ temperature increase with depth;
d. _____ average rate of seismic wave velocity in the
mantle;
e. _____ elastic rebound potential.
10. A P-wave is one in which
a. _____ material moves perpendicular to the direction
of wave travel;
b. _____ Earth's surface moves as a series of waves;
c. _____ material is expanded and compressed as the
wave moves through it;
d. _____ large waves crash onto a shoreline following a
submarine earthquake;
e. _____ none of these.
11. How does the lithosphere differ from the
asthenosphere?
12. Refer to the graph in Figure 8.9b. A seismograph in
Berkeley, California, records the arrival time of an
earthquake's P-waves as 6:59:54 P . M . and the S-waves as
7:00:02 P . M . The maximum amplitude of the S-waves as
recorded on the seismogram was 75 mm. What was the
magnitude of the earthquake, and how far away from
Berkeley did it occur?
13. What is the difference between an earthquake's focus
and its epicenter? Why is an earthquake's epicenter the
location that is usually reported in the news?
14. How does the elastic rebound theory account for the
energy released during an earthquake?
15. Why do insurance companies use the qualitative
Modifi ed Mercalli Intensity Scale instead of the
quantitative Richter Magnitude Scale in classifying
earthquakes?
16. What is the likely explanation for changes with depth
in the mantle?
17. Describe the various ways that earthquakes are
destructive.