Definitions - Continued

DOE-STD-1024-92

elastic system vibrates when it is set in motion by a single impulse and not influenced

by other external forces or by damping. The reciprocal of fundamental period.

PEAK GROUND ACCELERATION: The maximum horizontal component of ground

HORIZONTAL acceleration measured in the free field at the ground's surface during

an earthquake.

PERFORMANCE GOAL: It is the mean annual probability of exceedance of

acceptable behavior limits used as a target to develop natural phenomena hazard

mitigation requirements.

PERIOD: The time interval required by one full cycle of wave.

PROBABILISTIC SEISMIC HAZARD ANALYSIS: It is the calculation of probabilities

of future earthquake effects (primarily ground shaking) at a site for a specified period

of time. All possible tectonic events that could impact the site and the associated

ground motions are modeled, taking into account both the likelihood of occurrence,

and the uncertainty in input parameters such as seismic source, seismicity, and the

PSEUDO-MEAN: The (peak ground acceleration) probabilistic mean seismic hazard

estimate as developed in this standard based on the fractiles between the 15th

percentile and the 85th percentile from the LLNL and EPRI studies.

RESPONSE SPECTRUM: The peak response of a series of simple harmonic

oscillators of different natural period when subjected mathematically to a particular

ground motion. The response spectrum may be plotted as a curve on tripartite

logarithmic graph paper showing the variation of the peak spectral acceleration,

displacement, and velocity of the oscillators as a function of vibration period and

damping.

SITE AMPLIFICATION: An increase in seismic signal amplitude within some range

of frequency as waves propagate through different Earth materials. The amplitude

may be decreased in another frequency band.

SITE-SPECIFIC RESPONSE SPECTRA: As opposed to generic response spectra

these spectra developed for a specific site taking into consideration the local site

conditions and the regional geology and tectonics. The development of these are

governed by specific methods and requirements per the prevailing codes and

standards.