Geology Reference
In-Depth Information
17.
In the San Andreas Fault example (questions 4 and 5
above), lateral stream offset was an important clue to move-
ment along the fault. Follow the traces of streams in Figure 6.11
as they flow west from the mountains to the valley. Is there
any offset of streams where they cross the fault(s)? Why or
why not?
near a building. Nonstructural hazards can be caused
by things the occupants of a building do, such as hang-
ing plants or positioning bookshelves, or they may
arise from the failure of the integral components of
buildings such as water pipes, ventilation systems,
and electrical systems. Nonstructural hazards may
also be external, such as decorative trim that can fall
off a building (Figure 6.15) or glass that can break out
of windows. In summary, nonstructural hazards
include building furniture, utility systems, and inter-
nal and external trim and decoration. The behavior of
these items in an earthquake can cause damage,
destruction, and injury, even if the building remains
standing during and after an earthquake.
According to the U.S. Geological Survey, falling
objects and toppling materials present the greatest
hazards in earthquakes. Falling objects account for
about two-thirds of the casualties from earthquakes.
Also, replacement of these materials and loss of build-
ing use can be very expensive.
In this exercise you will draw a careful sketch of
a room (or other indoor site) and complete a checklist
to identify and comment on the hazards you find.
18.
Can you tell from the map (Figure 6.11) which side of the
fault has moved up and which side has moved down?
Describe your evidence. What additional kinds of informa-
tion might be helpful in determining the movement along
the fault?
Faults in Forests (Bainbridge Island, Washington)
Urban areas and thick forests are two environments in which
it can be difficult to locate active or potentially active faults.
In urban areas, faults may only be exposed in excavations for
construction, or detectable if there is offset of roads or struc-
tures. In forested areas, virtual deforestation provided by
LIDAR can allow the identification of faults. The example
below is from such a forested area.
QUESTIONS (6, PART C)
1.
Select a site that you frequently use. Make a sketch of this
room on the graph paper provided in Figure 6.16. The choice
of site is up to you. It could be a dorm room, a bedroom at
home, a place where you work, a place where you study, or
some other room or facility. You may do a map view or an
elevation, but there is no need to do both. Identify and label
the nonstructural hazards that you find. Include a scale on
your drawing.
19.
Look at the aerial photograph in Figure 6.13. Identify on
this figure any linear zones you see that might be faults,
being careful to avoid roads and property lines that are
marked by cut forests.
20.
Figure 6.14 is a LIDAR image of the same area, processed
to remove the forest from the image. Mark on this figure any
traces of faults that you see. Compare the trace of the fault
with the drawings in Figures 6.7 and 6.8. What are the sur-
face features that you see along the fault? What kind of fault
movement and offset is most likely here? (Circle One) Nor-
mal, Reverse, Strike slip?
2.
The list in Table 6.5 identifies some of the nonstructural
hazards that you may encounter in your search. This list is
not intended to be comprehensive; there are undoubtedly
some missing hazards. Space is left at the bottom of the list
for you to add other hazards that you discover.
Identify the room and building in the table title. Then
identify all hazards in the room that you select. In the space
provided, make brief comments about the specific nature of
each hazard and your vulnerability (such as "Textbooks in
environmental geology may fall off shelf and hit me").
Remember, in analyzing earthquake hazards you need to
imagine what would happen to the objects around you if
they were suddenly launched horizontally.
PART C. RECOGNITION
OF NONSTRUCTURAL HAZARDS
This exercise looks at the recognition of nonstructural
earthquake hazards and approaches the question, how
safe are we in our daily lives? Recognition of nonstruc-
tural hazards, however, is something that everyone
should know to be able to lead safer lives in earth-
quake country.
The structure of a building consists of those parts
that help it stand up and withstand the forces of
weight, wind, and earthquakes that may impact it.
Everything else in a building is nonstructural. Struc-
tural failure can cause partial or total collapse of a
building and injury or death to occupants and those
PART D. EARTHQUAKE PREPARATION
AND HAZARD REDUCTION
This exercise explores specific coping techniques to
reduce earthquake hazards and improve safety during
and after an earthquake. Consider situations in which
electric power and water supplies are not available;
ATMs, credit cards and other sources of money are not
