Environmental Engineering Reference
In-Depth Information
Fault
recurrence
model
Seismic
sources
Segments
Attenuation
relationship
Segmentation Segmentation
model
Status of
activity
Total fault
length
Dip
Maximum
magnitude
Recurrence
data
Recurrence
rate
Unnamed
5000
0.04
3333
0.28
2500
0.48
2000
0.16
1667
0.04
8.5
0.333
Unsegmented
0.2
Cominston
Ogden
65
°
0.5
Oquirrh Mtns
Model A
Active
37 km
Campbell
SLC
Wasatch
Fault
1.0
1.0
1.0
0.4
Provo
7.0
0.333
East coshe
Segmented
0.15
45
°
0.5
Nephi
Levon
7.25
Exponential
West valley
Hansel valley
0.7
7.5
0.8
0.3
Model B
0.15
Segment
6.0
0.3
Sadigh
Bear lake
Backgnd
1.0
0.6
Active
0.333
6.25
9.3
0.334
9.8
0.5
6.5
N/A
N/A
1.0
N/A
N/A
N/A
Characteristic
0.2
0.333
0.7
Joyer
−
fumal
0.333
FIGURE 11.51
Example of logic tree simulation for seismic forces to assess regional earthquake hazards and risk along the
Wasatch Fault, Utah. (From Youngs, R.R. et al.,
Assessment of Regional Earthquake Hazards and Risk along the
Wasatch Fault, Utah,
Gori, P.L
.
and Hays, W.W., Eds., U.S.G.S. Open File Rep. 87-585, 1987, pp. M1-M110.
With permission.)
design criteria. A guide to international seismic codes is available from the
National Center
for Earthquake Engineering Research
(NCEER), in Buffalo, New York.
Data adequacy
is evaluated. Codes, strong-ground-motion records, response spectra,
recurrence studies, microzonation maps, etc. may provide information adequate for
design, or a suitable design earthquake or other design basis may have already been estab-
lished for the area. The possible impact of a nearby reservoir on induced seismicity should
be considered (
Section 11.2.1)
.
The Natural Environment
Purpose and Scope
The purpose of a review of existing data is the identification of important natural factors
affecting the suitability of the site location from the viewpoint of hazard degree and the
anticipation of potential foundation problems. Items of interest are physiography, climate,
and geology. In addition to the collection and review of existing data, new data may be
generated during the preliminary phase by terrain analysis techniques and field recon-
naissance. Data are also collected for other environmental aspects including flora and
fauna, but are not included in the scope of this discussion.
Physiography
Information on physiography is obtained from topographic maps and remote-sensing
imagery. The importance of physiography lies in its direct relationship in many cases to
the geologic hazards, and with respect to seismicity it influences attenuation (
Section
11.2.6),
although the relationships are not well defined. Some very general associations
may be established:
Mountainous regions
: Characteristic features are slope failures, variable regional
geology, intense surface fault systems, and, in some locations, volcanoes.
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