Environmental Engineering Reference
In-Depth Information
118˚
I - IV
119˚
8
Woody
8
Kernville
7
8
7
7
I - IV
9
7
7
White Wolf
fault
BAKERSFIELD
Caliente
8
7
7
8
8
11
7
8
9
Buena
vista L.
7
8
7
10
Taft
Tehachapi
7
10
8
7
10
8
10
10
7
7
8
Wheeler Ridge
8
8
8
35˚
9
10
7
7
Miles
8
9
5
10 15
05
9
V
I - IV
VI
V
36
°
I - IV
VI
VII
VIII-IX
VI
34
°
V
V
Approximate location of
the San Andreas fault
I - IV
32
°
0
25
50
75
100
Miles
FIGURE 11.9
Intensity distribution of the July 21, 1952, earthquake in Kern Country, California, which occurred along the
“inactive” White Wolf fault. (After Murphy, L.M. and Cloud, W.K.,
Coast and Geodetic Survey, Serial No. 773,
U.S. Govt. Printing Office, 1954.) The map has been overlaid onto the physiographic diagram of southern
California for comparison with geologic conditions as revealed by physiography. (Physiographic diagram from
Raisz, E.,
Map of the Landforms of the United States,
4th ed., Institute of Geographical Exploration, Harvard
University, Cambridge, Massachusetts, 1946.)
Surface wave magnitude
(
M
s
) used to measure larger quakes (
M
L
6.5 to ~ 8.5).
●
Moment magnitude
(
M
W
) which is not based on seismometer readings, but on the
energy released by the earthquake, termed the
seismic moment
(
M
o
).
M
o
●
rock rigid-
ity (shear modulus)
average physical area of the fault
the distance of fault slip.
Significance of Magnitude
Amplitudes vary enormously among different Earthquakes. An increase in one magnitude
step has been found to correlate with an increase of 30 times the energy released as seis-
mic waves (Bolt et al., 1975). An earthquake of magnitude 8.0, for example, releases almost
1 million times the energy of one of magnitude 4.0, hence the necessity for a logarithmic
scale. The largest quakes have had a magnitude of 8.9 (
Table 11.1)
.
In general, magnitudes
