Definitions - Continued - std102395

DOE-STD-1023-95

Near-Field A region within 15 km (9.3 mi) of a seismic source.

NPH Mitigation An action taken to reduce the impacts of natural phenomena hazards (to become less

harsh or hostile to workers, the public, facilities, and the environment). This includes NPH resistant

design, evaluation, construction requirements, and operational procedures.

One-(Five-)Hundred-Year Flood A flood level which will be equaled or exceeded with a 1.0 (0.2)

percent chance in any given year.

Overland Runoff The portion of precipitation which is not absorbed or evaporated and which flows

overland into depressions, lakes, rivers, or oceans.

Peak Flow The maximum flow rate that occurs during a flood event.

Peak Ground Acceleration (PGA) The largest ground acceleration produced by an earthquake at a site.

Unless otherwise noted, it usually refers to the horizontal ground motion, i.e., the average of the two largest

horizontal acceleration components of the earthquake ground motion at a site. The peak ground

acceleration, the peak ground velocity (PGV), and the peak ground displacement (PGD) are parameters

customarily used to characterize the level of earthquake ground motion.

Peak Ground Displacement (PGD) The largest ground displacements produced by an earthquake at a site.

Peak Ground Velocity (PGV) The largest ground velocity produced by an earthquake at a site.

Performance Category (PC) A classification using a graded approach in which structures, systems, or

components in a category are designed to assure similar levels of protection (i.e., meet the same

performance goal) during natural phenomena hazard events.

Performance Goal The mean annual probability of exceedance of acceptable behavior limits used as a

target to develop natural phenomena hazard mitigation requirements as specified in DOE-STD-1020-2002.

Probabilistic Method A technique which uses distributions of parameters (including uncertainty and

randomness) to perform an analysis. Results are expressed in terms of probabilistic distributions which

quantify uncertainty.

Probability of Exceedance The probability that a specified level of hazard occurrences or specified social

or economic consequences of NPHs, will be exceeded at a site or in a region during a specified exposure

time.

Response Spectrum A curve calculated from an earthquake accelerogram that gives the value of peak

response in terms of acceleration, velocity, or displacement of a damped linear oscillator (with a given

damping ratio) as a function of its period (or frequency) of vibration. For design purposes, a set of response

spectra are usually generated for different damping ratios.

Seiche A cyclic oscillation or sloshing of a lake or large body of water due to the effect of winds, seismic

forces, and/or atmospheric pressure.