Environmental Engineering Reference
In-Depth Information
0.8
Firm ground
High intensity sources
Medium intensity sources
90% expectation ranges
0.6
El Centro (N-S) 1940
Castaic 1971
Parkfield 1966
Taft 1952
Vernon 1933
0.4
0.2
0
20
40
60
80
100
120 km
Distance
FIGURE 11.29
Attenuation of maximum acceleration with distance from fault rupture for California earthquake prepared
from strong-motion records. Frequencies are less than 8 Hz, and generally in the low to intermediate range.
Acceleration is for rock or strong soils. (After Bolt,
5th World Conference on Earthquake Engineering
, Rome, 1973.)
1.4
M = 8
1.2
7.5
7
1.0
0.8
6.5
0.6
6
FIGURE 11.30
Relationship between predominant
periods of maximum acceleration,
magnitude, and distance from the
causative fault. (From Seed, H.B. et al.,
Proc. ASCE, J. Soil Mech. and Found.
Eng. Div.,
95, 1969. With permission. As
presented in Atomic Energy
Commission, 1972.)
5.5
0.4
0.2
0
0
25
50
75
100
125
150
175
200
225
Distance from causitive fault (mil)
Isoseismal Maps
The strong relationship between intensity distribution and fault rupture, where rupture
length is long, is illustrated in
Figure 11.31,
the intensity distribution for the San Francisco
1906 earthquake. Intensities generally of VIII to IX are given along the fault, but intensi-
ties of IX are given also in isolated areas as far as 64 km from the fault. Two branches of
the San Andreas Fault are also shown, the Hayward and the Calaveras faults. The map
suggests that movement may have also occurred along these faults during the 1906 quake.
Seismicity Maps and Tectonic Structures
In studies for seismic design, seismicity maps are overlain with geologic maps to obtain
correlations with tectonic structures. For example, a comparison of the seismicity map of
