Definitions - std10240032

DOE-STD-1024-92

DEFINITIONS

ATTENUATION: (1) A decrease of signal amplitude during transmission; (2) a

reduction in amplitude or energy with or without change of waveform; or (3) the

decrease in seismic signal strength with distance which depends not only on

geometrical spreading but also may be related to physical characteristics of the

transmitting medium causing absorption and scattering.

DAMPING: The reduction in amplitude of an oscillation owing to absorption of energy

within a material.

DETERMINISTIC SEISMIC HAZARD ANALYSIS: A deterministic seismic hazard

analysis uses one tectonic structure, tectonic province, or capable fault and one

attenuation relationship to estimate effects of ground motion at a site.

EUS: Eastern United States sites, east of about longitude 104W in U.S.A. The

counterpart is WUS.

EXTENDED SOURCE SEISMIC HAZARD ANALYSIS: A special seismic hazard

analysis that considers the extent and orientation of ruptures from large earthquakes

in a specific region. The finite-rupture analysis considers multiple alternative

interpretations in order to characterize uncertainty in the seismic hazard. (Among

DOE sites, Paducah, Kentucky site, as a results of the proximity to potential large

earthquakes similar to New Madrid, Missouri earthquakes of 1811 and 1812 has need

for such an analysis).

FREE FIELD: Refers to ground motion measurements that are not influenced by

manmade structures.

GEOMETRIC MEAN: The geometric mean for a sample of size n - (X1 x X2 -.. x Xn) 1/n

versus an arithmetic mean which is (X1 + X2 ..+ Xn) 1/n.

GROUND MOTION: General term referring to the qualitative or quantitative aspects

of shaking of the Earth's surface from earthquakes or explosions.

HAZARD (SEISMIC) EXCEEDANCE PROBABILITY: The probability over some

period of time that an earthquake will generate a level of ground shaking greater than

some specified level.

HERTZ (HZ): A unit of frequency. Expressed in cycles per second.

MEAN: Very briefly the mean is the first moment. It is that value about which the

entire empirical distribution could be "balanced."

MEDIAN: The median is any value of' X such that one-half the values are above and

one-half below it (it divides the area of the histogram in half).

NATURAL FREOUENCY(IES): The discrete frequency(ies) at which a particular