Environmental Engineering Reference
In-Depth Information
Bakersfield
10
15
San Andreas fault
Maricopa
Mojane
Barstow
Palmdale
Cajon
Amboy
15
10
10
5
0
3
Ventura
40
45
Los Angeles
San
Fernando
Palm
Springs
Blythe
Tidal
8
15
1904 Break
1952 Break
1957 Break
1971
Break
San Diego
Area tilted down to the north
since early 1974
3 5
Isobase,showing elevation changes
between 1959 and 1974; contour
interval 5 cm.
FIGURE 11.23
Contours of surface warping (cm), area of Palmdale, California. Area uplifted 45 cm between 1959 and 1974,
but between 1974 and 1977 an area at Palmdale had dropped 18 cm. Recent surveys show that the uplifted area
is larger than previously thought, and that the shape and size of uplift change with time. (From Hamilton,
R.M., Geological Survey Circular 780, U.S. Department of the Interior, 1978. With permission.)
have been, and are being installed, around historically seismically active areas. They con-
tinuously monitor and record horizontal and vertical movements. InSAR complements
GPS data by providing an overview of whole regions on a periodic basis. In 2000, NASA
began the Global Earthquake Satellite System (GESS) study, which advocates the installa-
tion of a number of satellites to transmit InSAR imagery.
National Center for Earthquake Research (USGS) Menlo Park, California, was established
in 1966. An array of monitoring instruments were installed along the Hayward Fault in the
San Francisco Bay area and the San Andreas Fault in Parkfield (1985). Included for continu-
ously monitoring movements are creepmeters for near-surface movement, tiltmeters for
ground rotation and tilting, dilatometers for volumetric contraction and extension, borehole
tensor strainmeters for directional contraction and extension, and GPS systems. Some instru-
mentation used to monitor ground changes is described in Section 4.5.7.
The San Andreas Fault Observatory at Depth (SAFOD) is a deep borehole observatory
proposed to measure the physical conditions under which plate boundary earthquakes
occur. Planned for 2004, it is designed to directly sample fault zone materials, and moni-
tor the San Andreas Fault zone near Parkfield. Moderate-size earthquakes of about M
6
have occurred on the Parkfield section of the fault at fairly regular intervals: 1857, 1881,
1901, 1922, 1934, and 1966. The location of Parkfield is given in Figure 11.24a; an intensity
map of the 1966 event is given in Figure 11.24b.
A 3.2-km-deep hole will be drilled through the fault zone close to the hypocenter of the
 
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