0.50 



0.45 



0.40 



0.35 



0.30 



g 0.25 



< 



6 



1 0.20 



0.15 



0.10 



; = Richter earthquake 

 magnitude 



20 40 60 80 100 120 140 160 



Distance from Epicenter (km) 



I 1 1 1 1 1 1 1 1 



12.5 25 37.5 50 62.5 75 87.5 100 



Distance from Epicenter (miles) 



Figure 6-9. Maximum acceleration associated with earthquakes of various 

 magnitudes (from Seed et al., 1969). 



major earthquakes. While the shear in the soil may be increased, the 

 effect on anchor capacity is unknown. A granular soil's susceptibility 

 to strength reduction during an earthquake is primarily a function of 

 its descriptive relative density (i.e., loose, dense), and partially a 

 function of soil depth. The criteria for liquefaction are given in 

 Figure 6-10 for two peak acceleration levels. Interpolation or limited 

 extrapolation can be used to assess stability at a site based on the 

 exact value of peak acceleration determined from Figure 6-9. Condi- 

 tions should be assessed at the depth of the keyed anchor and just 

 above it. If analysis of a site and its expected earthquake indicates 



58 



