Appendix A: Guidelines for Acceptable Methods to Meet NPH Acceptance Criteria

DOE-STD-1023-95

= 4.6, consistent with the lower bound used for national seismic hazard maps, e.g. BSSC

(1988).

The hazard model is developed by examining characteristics of seismic sources and their

contribution to the seismic hazard of the site (Cornell 1968). For a detailed description of

acceptable methodologies, see SSHAC (1997).

The following discussion summarizes the four standard steps in the methodologies.

Step 1:

A zonation map is developed (with possibly additional information on the spatial

distribution of earthquakes in any given zone). The zonation is a partition of the

entire area of interest into independent seismic source zones. Each zone is

assumed to be a unique source of earthquakes and to have its own recurrence

distribution. A zone can be described by an area or a fault (such as for western

U. S. Sites).

Step 2:

The recurrence (frequency-magnitude distribution) is defined for each zone. This

step quantifies the total number of earthquakes greater than magnitude Mo

expected to occur during the period of interest (usually one year), and it

describes the relative frequency of all the magnitudes greater than Mo. An

upper bound (maximum) magnitude is defined for each recurrence distribution.

Step 3:

The ground motion model provides the probability that g is exceeded at the site

(at a hypothetical rock outcrop) when an earthquake of magnitude m has

occurred at a given location. Usually, the direction of the origin of the

earthquake is neglected and only the distance r to the site is considered in the

ground motion modeling:

P (G g, for given m and r).

The measure of the source-to-site distance may vary depending upon the

procedure used to estimate earthquake attenuation effects.

For a site where the ground motion model is not specifically applicable to the

local geology, a site response evaluation should be completed. The site response

evaluation should consider field investigations, sampling, and testing as

described in DOE-STD-1022-94.

The site correction should be applied consistent with McGuire, et. al. (2001).

Step 4:

The hazard curve SH(g) is calculated by integrating the effects of all possible

earthquake locations and all possible earthquakes with magnitudes greater than

Mo occurring within all seismic source zones. The seismic hazard curve

expresses the annual frequency of exceeding particular ground motion levels.

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