Geology Reference
In-Depth Information
8. a.
What was the maximum intensity for the 1965 earthquake?
approximate threshold for damage to older (pre-1965)
structures. Additional information on these maps is
available from Frankel et al. (1997) and from the USGS
(Fact Sheet 183-96).
Figure 6.3 is a ground-shaking hazard map that
shows a 10 percent probability of exceeding a given
value in a 50-year period (Peterson and others, 2008).
That is, over the next 50 years there is a 1 in 10 chance
that the acceleration given for any area will be exceeded.
Use information in Figure 6.3 to help answer the follow-
ing questions.
b.
Where does the epicenter for the 1965 earthquake
appear to have been?
9.
On the Web you will find additional information on these
two earthquakes (and others) at
http://earthquake.usgs.gov/
eqcenter/dyfi.php. Complete the following blanks for these
two western Washington earthquakes.
a.
1949 Earthquake
1965 Earthquake
QUESTIONS (6, PART A4)
1.
Which areas of the country have the lowest hazard from
earthquake shaking (where 4% g, or less, peak acceleration is
expected)?
Date
Maximum Intensity
2.
If damage to older (pre-1965) structures can be expected
with horizontal accelerations of 10% g or more, which areas
of your home state are:
a.
at some risk?
Name (Earthquake)
Magnitude
b.
at greatest risk?
Number of Reports
c.
what is your home state?
b.
You might still be curious about earthquake intensities.
Below write a question for your TA or instructor about
some aspect of the exercise that you don't understand.
3. What three or four regions of the country have the highest
accelerations?
Note: If you experience an earthquake you can report
what you saw/felt during the earthquake and what damage
you noted. It is useful to write your account of the event as
soon as you are safe and can make notes. Then use those
notes when completing the form at
http://pasadena.wr.usgs
.gov/shake/pnw/html/unknown_form.html.
4. What geologic processes, other than shaking and fault dis-
placement, could produce a hazard in an earthquake? List two.
Earthquake Shaking Hazard Maps (6, Part A4)
5.
The geologic material on which a building rests plays a
role in the type of shaking that occurs during an earthquake.
Weak materials amplify the shaking. Which of the following
foundation materials would most likely result in less shak-
ing and a safer building? (circle one)
National maps of earthquake shaking hazards provide
information that helps to save lives and property by
providing data for building codes. Buildings designed
to withstand severe shaking are less likely to injure
occupants. These hazard maps are also used by insur-
ance companies, FEMA (for support of earthquake
preparedness), EPA (for landfill design), and engineers
(for landslide potential).
The map shows the hazard by zones (or in some
maps contour peak values) of the levels of horizontal
shaking. The higher the number the stronger is the
shaking. The number is % g or percent of acceleration
due to gravity (in this case as horizontal acceleration).
Acceleration is chosen, because building codes pre-
scribe how much horizontal force a building should be
able to withstand during an earthquake. 10% g is the
artificial fill, poorly consolidated sediments, marine clays,
unweathered bedrock
6.
If the Internet is available, now or after class, determine
and list (places and magnitudes) where the largest two
earthquakes have occurred in the last 2 weeks. Also list what
processes, other than shaking, contributed to the loss of
structures and life. A possible source to begin the search is:
