3-4.5.3

a. Earthquake Loads: Follow the provisions of *Marine Oil Terminal*

acceleration values for earthquakes with a 2 and 10 percent probability of

exceedance in a 50-year period are typically well defined. To obtain seismic

spectral accelerations for other recurrence intervals use the following formula

based upon the procedure presented in Section 1.6.1.3 of *Prestandard and*

Si = Si(10/50) (Ci),

where:

Si

= Spectral acceleration parameter("i" = "s" for short-period, or "i" = "1" for 1

second period)

second period) at a 10% probability of exceedance in 50 years

= Modifier provided in Tables 3-4 and 3-5 below("i" = "s" for short-period, or

Ci

"i" = "1" for 1 second period).

Design Earthquake Probability of Exceedance in 50 Years

Region

10 %

15 %

20 %

50 %

65 %

75 %

California

1.0

0.83

0.72

0.44

0.36

0.32

Pacific

1.0

0.79

0.67

0.36

0.29

0.25

Northwest

Eastern US

1.0

0.72

0.56

0.23

0.17

0.14

Other locations

1.0

0.79

0.67

0.36

0.29

0.25

Notes:

1. The modifier Cs includes a statistical adjustment factor, "*P*R ", and a location adjustment factor, "n",

as defined in section 1.6.1.3 in *Prestandard and Commentary for the Seismic Rehabilitation of*

continental US.

2. This table is valid at locations where the Mapped MCE spectral acceleration for short-periods, SS,

is less than 1.5g.

66

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