The development of site-specific spectral shapes for PC 3 SSCs

DOE-STD-1023-95

magnitude of earthquakes that were modeled for the source. Likewise, the level of recorded

ground motions for the event can be compared with the levels predicted in the seismic hazard

analysis. For additional guidance on the content and amount of documentation to support

PSHAs, SSHAC (1997) should be consulted.

A3.1.3.1-a. The development of site-specific spectral shapes for PC 3 SSCs may be relatively less rigorous

than those in PC 4. For example, the treatment of degradation and uncertainty in soil

properties in site response analysis may be made by using generic characteristics rather

than using data from site-specific tests. The bounding limits of magnitudes and distances for

collecting data may also be reduced.

A3.1.3.1-b. An acceptable approach for the development of site-specific DBE response spectra includes the

steps summarized below:

Step 1:

From the site-specific probabilistic seismic hazard analysis results, use the mean

seismic hazard curve showing the annual probability of exceedance as a function

of the SA (for additional guidance on this and subsequent steps, see USNRC,

1997 Regulatory Guide 1.165). It is recommended that, as part of the

information database, the following deaggregation procedure also be applied to

median hazard results.

Using the appropriate annual probability of exceedance value, PH (e.g., 1x10-4

Step 2:

for PC 4), enter the hazard curve from Step 1 at PH to determine the

corresponding SA.

Step 3:

Deaggregate the mean SA seismic hazard curve as a function of magnitude and

distance and calculate the contribution to this hazard curve for all of the

earthquakes in a selected earthquake magnitude and distance set (size M x N) to

determine the relative contribution to the hazard. This requires the calculation of

the annual probability of exceedance, H(mi,rj), for each magnitude/distance bin:

magnitude mi (i =1,2,..,M) and distance rj, (j =1,2,...,N).

Step 4:

Compute the magnitude of the controlling earthquake for the mean estimates of

SA (5-10) using the contributions H(mi, rj) computed in Step 3 in accordance

with the following (or similar) equation:

M N

mi H(mi,rj) /

H(mi,rj)

M(1) =

i=1 j=1

A-5