Geology Reference
In-Depth Information
FIGURE 9.3 Land subsidence (in ft) in the Santa Clara Valley, 1934-67 (Poland, 1971).
6. Would you expect any subsidence in the areas marked
with diagonal lines?
Damage to well casings in the valley due to subsidence
has amounted to over $4 million. Even greater damage
occurred in the northern part of the valley because more
than 17 square miles sank to below highest tide and protec-
tive works had to be installed. The fluctuations in water level
in an 840-foot deep well in San Jose are shown in the hydro-
graph in Figure 9.4. This record shows the changes between
1915 and 1967.
Explain.
7. Figure 9.3 shows the total subsidence for the central part of
the valley from 1934 to 1967. What was the annual rate of
subsidence for the area around the highway junction
(Bayshore Highway and #9) north of Sunnyvale and east of
Mountain View from 1960 to 1967? (First refer to Figure 9.2.)
10. What was the water level in the well in 1915? .
In 1967?
11. During what period would this artesian well have been a
flowing well?
8. Where had the maximum subsidence occurred by 1967?
9. What was the increase in subsidence between 1960 and
1967 on the Bayshore Highway south of Agnew?
12. a. How many highs and lows occur in the water level in
any 5-year period? (Figure 9.4)
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