Fig. 1  Design response spectral.

  Their expression are:
              For   
   For   
   For   
Where:
Ss = Sorted spectral reference for T = 0.20 sec. (see Table 5 , Map 1)
S1 = Sorted spectral reference for T = 1.00 sec. (see Table 5, Map 1)
Fa = Factor of soil associated with short periods. (Table 1, Table 3)
Fv = Factor of soil associated with long periods. (Table 2,Table 3)
T = Fundamental period (see Equation 5 and Equation 6)

  Table 3  Seismic Zoning. (Ss Value and S1)

Zone Ss S1
I 1.55g 0.75g
II 0.95g 0.55g
Seismic Zone (See Fig. 2)

  Table 4  Site factor values (Fa)

Site
Class		 Spectral acceleration reference for short periods (Ss) to
Ss = 0.30 Ss = 0.40 Ss = 0.50 Ss = 0.60 Ss = 0.70 Ss = 0.80 Ss >= 0.90
A 0.8 0.8 0.8 0.8 0.8 0.8 0.8
B 0.8 0.8 0.8 0.8 0.8 0.8 0.8
C 1.2 1.2 1.2 1.2 1.1 1.0 1.0
D 1.6 1.5 1.4 1.3 1.2 1.2 1.2
E 2.3 2.0 1.7 1.5 1.3 1.1 1.0
F Note b Note b Note b Note b Note b Note b Note b
a. Use linear interpolation to map values not included Table 4
b. F for the site should be a dynamic analysis of soil to determine the factor Fa appropriate.

  Table 5  Site factor values (Fv)

Site
Class		 Spectral acceleration reference for long periods (S1)a
S1 = 0.20 S1 = 0.30 S1 = 0.40 S1 >= 0.50
A 0.8 0.8 0.8 0.8
B 1.0 1.0 1.0 1.0
C 1.6 1.5 1.4 1.3
D 2.0 1.8 1.6 1.5
E 3.2 2.8 2.4 2.4
F Note b Note b Note b Note b
a. Use linear interpolation to map values not included Table 5
b. F for the site should be a dynamic analysis of soil to determine the factor Fv appropriate.

  Table 6  Site Class

Site Class Zone I,II
Fa Fv
A 0.8 0.8
B 1.0 1.0
C 1.0 1.3
D 1.0 1.5
E 1.0 2.4
F Note b Note b
For site class see Table 7.

  Table 7  Soil Classification

Classification Designation Average property in the first 30m
Velocity of shear wave, Vs (m/s) Standard penetration resistance, N Shear strength of the soil without Su, (Kg/cm2)
A Hard rock Vs > 1500 N/A N/A
B Rock 760 < Vs <= 1500 N/A N/A
C Very dense soil and soft rock 360 < Vs <= 760 N > 50 Su >= 1.0
D Rigid soil 180 < Vs <= 360 15 <= N <= 50 0.5 <= Su <= 1.0
E Soft ground Vs < 180 N < 15 Su < 0.5
E - Any layer of soil with more than 3 m has the following characteristics:
1. Plasticity Index (a) PI > 20.
2. Moisture content (b), w >= 40%.
3. Undrained shear strength Your < 0.2 Kg/m2.
F - Any soil that has one or more of the following characteristics:
1. Soil liquefaction could suffer during strong earthquake.
2. "Mobs" and / or clays with a large amount organic material with more than 3 m
Thickness.
3. Clays with a plasticity index > 75 and a thickness greater than or equal to 7.5 m
4. Soft clays with a thickness greater than or equal to 35.0 m and His <= 0.50 Kg/cm2

N / A: Not applicable
(a) The Plasticity Index PI is defined in ASTM D4318.
(b) The moisture content was determined according to ASTM D2216.
(c) The undrained shear strength of each stratum was determined according to ASTM D2166 o ASTM D2850.