Environmental Engineering Reference
In-Depth Information
2-4
2-4
4-8
4-8
8-16
8-16
16-24
16-24
32+
Hawaii
32+
Alaska
24-32
4-8
16-24
8-16
16-24
8-16
24-32
4-8
0-2
8-16
4-8
4-8
2-4
16-24
4-8
2-4
32+
2-4
8-16
4-8
0-2
8-16
24-32
16-24
2-4
24-32
2-4
Highest hazard
32+
32+
8-16
4-8
32+
8-16
4-8
4-8
24-32
16-24
16-24
2-4
%g
8-16
0-2
4-8
0-2
2-4
0-2
Lowest hazard
FIGURE 11.14
Peak acceleration (% g ) with 10% probability of exceedence in 50 years. (Courtesy of USGS, National Seismic
Hazard Mapping Project.)
strong motion recordings. The most common is the stochastic method in which the Fourier
amplitude spectrum (FAS) of the average component of ground motion is described by the
general relation (Campbell, 2003)
A (
ƒ
)
Src(
ƒ
) Attn(
ƒ
, R ) Amp(
ƒ
)
(11.11)
where Src(
, R ) describes the attenu-
ation caused by wave propagation through the crust (site-to-source distance), and Amp(
ƒ
) describes the earthquake source (magnitude), Attn(
ƒ
)
describes the response of materials (geological conditions) beneath the site. Relatively
complex equations describe each of the elements of Equation 11.11.
ƒ
Engineering Models
A large number of attenuation relations have been developed to prepare engineering esti-
mates of strong ground motion throughout the world. Campbell (2003) describes four
models for “shallow active crust” in Western North America, three for “shallow stable
crust” in Eastern North America, and several others for Europe, Japan, and worldwide.
The various parameters in these models include ground motion, magnitude, distance,
depth, faulting mechanisms, the site geologic conditions, fault hanging and foot-wall
locations, source (fault) directivity (conditions), plus a number of miscellaneous parame-
ters, described in detail by Campbell (2003). He notes that “all engineering models have
limitations that results from the availability of recordings, the theoretical assumptions
 
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