Standardized DBE Response Spectra

DOE-STD-1023-95

several controlling earthquakes for a site; e.g., a moderate nearby earthquake may control the high-

frequency ground motions or the PGA, and a large distant earthquake may control the low-frequency

ground motions (e.g., 1-2.5 Hertz) or the peak ground displacement (PGD).

For many cases of interest, the primary controlling earthquake is the postulated event that governs

the spectral accelerations in the 5 to 10 Hz range. Thus, the primary seismic ground motion

parameter is the average spectral acceleration of 5 and 10 Hz, SA (5-10). There may be some

instances where the spectrum generated from this controlling earthquake may not be sufficiently

broad-banded to capture the contributions from all sources. Therefore, if the controlling earthquake

for the frequency range of 1 to 2.5 Hz is from a significantly different source, e.g. a large, distant

event, its effect on the spectral shape shall be included. In addition, for sites that have SSCs

sensitive to low-frequency seismic response (e.g., below 1 Hz), it may be necessary to include the

controlling earthquake based on seismic PGD. It should be noted that these primary frequency

ranges of interest may be modified for cases of soft structures or for structures on soft soil sites.

3.1.3.2 Standardized DBE Response Spectra

As specified in Section 3.1.1.b, standardized response spectra developed from general site conditions

instead of site-specific geotechnical studies are used if site-specific response spectra are unavailable.

Acceptable methods to generate site-dependent standardized response spectra include those of

Newmark and Hall (1978), Mohraz (1976), Seed et al. (1974), Kiremidjian and Shah (1980), ATC

(1984), and BSSC (1988). An example of the application of standardized spectra can be found in

Appendix A.

3.1.4 Earthquake-Induced Ground Failure Assessment

In addition to ground shaking, another direct effect of earthquakes can be surface expression of fault

offset. A probabilistic assessment of this ground failure mode may be necessary if potential fault

rupture may occur near a facility. If the annual probability of this ground failure mode is greater

than the necessary performance goal, either the site should be avoided, mitigation measures taken, or

an evaluation performed of the effects of fault offset. Similar comments can be made for other

potential sources of ground failure, such as liquefaction or lateral spreading.

3.1.5 Historical Earthquake Ground Motion Check

In assessing the DBE, the review will consider historical earthquakes that may have affected the site

and ensure that the DBE is conservative relative to the historical earthquake. This is not meant to be

a comparison to the "maximum credible" earthquake, nor should it include infrequent paleoseismic

events as part of the historical data set.

Historical earthquakes are defined as any earthquake which has been felt or instrumentally recorded.

Ground motion estimates will be completed for all historical earthquakes estimated to be equal to or

above moment magnitude of 6.0, within a distance of 200 kilometers (124 mi) of the site. The only

exception to this requirement is for sites within 500 kilometers (311 mi) of the 1811-1812 New

Madrid earthquake sequence, which are required to include the ground motion from a reoccurrence of

these events. Ground motion estimates shall be based on the following assumptions: