Seismic Hazard One form of natural phenomena hazards caused by earthquakes. The primary effect of
the seismic hazard is earthquake ground shaking. Other effects associated with the seismic hazard include
differential ground deformation induced by fault displacement, liquefaction, and seismic induced slope
instability and ground settlement.
Seismic Hazard Curve (SHC) A frequency of occurrence plot that characterizes the seismic hazard at a
specific site by giving the return period or annual probability of exceedance as a function of the peak
ground acceleration (PGA) or any other ground motion parameter; e.g., PGV, PGD, or average spectral
acceleration, used to characterize the level of earthquake ground motion at the site. The mean seismic
hazard curve is used to determine the DBE.
Seismic Sources Portions of the earth that have a potential for abrupt releases of energy in the earth's
crust (lithosphere), or to cause earthquakes. Seismic sources may include a region of diffuse seismicity
(seismotectonic province) and/or a well-defined tectonic structure which can generate both earthquakes and
Site The area with one or more DOE facilities or activities that can be represented by the same natural
phenomena hazard potential with local conditions that can be represented by the same parameters.
Stage Elevation above some arbitrary zero datum of the water surface at a gauging station.
Stage-Discharge Relation (Rating Curve) Relationship giving the discharge for each stage value.
Storm Surge A rise in water surface level above the normal level on a lake or ocean, produced by wind
and/or differences in atmospheric pressure during a storm.
Structures, Systems, and Components (SSCs) A structure is an element, or a collection of elements to
provide support or enclosure. A component is an item of equipment such as a pump, valve, relay, etc., or
an element of a larger array, such as a length of pipe, elbow, reducer, etc. A system is a collection of
components assembled to perform a function.
Transition Wind Speed The intersection point of the wind hazard curve based on a straight wind model
and the wind hazard curve based on a tornado model.
Tsunami A long period ocean wave caused by an underwater disturbance such as an underwater
earthquake, landslide, or volcanic eruption.
Water Surface Elevation The elevation, usually in relation to mean sea level or National Geodetic
Vertical Datum, reached by floods of various magnitudes.
Wind Hazard Curve A frequency plot which gives the basic wind speed as a function of the return period
or annual probability of exceedance. The mean wind hazard curve shall be used to determine the basic
wind speed for the design and/or evaluation of DOE facilities.
Windborne Missiles Wind hazard design parameters referring to debris transported by tornadoes and
other types of winds.