EP 1110-2-13
28 Jun 96
An emergency, in terms of dam operation, is a
A postulated seismic event, specified in terms of
condition which develops unexpectedly, endangers
specific bedrock motion parameters at a given site,
the structural integrity of the dam and/or downstream
which is used to evaluate the seismic resistance of
property and human life, and requires immediate
man-made structures or other features at the site.
action.
Earthquake, Operating Basis (OBE)
The earthquake(s) for which the structure is designed
Emergency Action Plan (EAP)
A plan of action to be taken to reduce the potential for
to resist and remain operational. It reflects the level
property damage and loss of life in an area affected
of earthquake protection desired for operational or
by a dam failure or large flood.
economic reasons and may be determined on a
probabilistic basis considering the regional and local
geology and seismology.
Energy dissipator
A device constructed in a waterway to reduce the
kinetic energy of fast flowing water.
Earthquake, Safety Evaluation (SEE)
The earthquake, expressed in terms of magnitude and
closest distance from the dam site or in terms of the
Epicenter
characteristics of the time history of free-field ground
The point on the earth's surface located vertically
motions, for which the safety of the dam and critical
above the point of origin of an earthquake.
structures associated with the dam are to be evaluated.
In many cases, this earthquake will be the maximum
Fault
credible earthquake to which the dam will be
A fracture or fracture zone in the earth crust along
exposed. However, in other cases where the possible
which there has been displacement of the two sides
sources of ground motion are not easily apparent, it
relative to one another.
may be a motion with prescribed characteristics
selected on the basis of a probabilistic assessment of
Fault, active
the ground motions that may occur in the vicinity of
A fault which, because of its present tectonic setting,
the dam. To be considered safe, it should be
can undergo movement from time to time in the
demonstrated that the dam can withstand this level of
immediate geologic future.
earthquake shaking without release of water from the
reservoir.
Fault, capable
An active fault that is judged capable of producing
macroearthquakes and exhibits one or more of the
Earthquake, synthetic
Earthquake time history records developed from
following characteristics:
mathematical models that use white noise, filtered
white noise, and stationary and nonstationary filtered
a. Movement at or near the ground surface at
white noise, or theoretical seismic source models of
least once within the past 35,000 years.
failure in the fault zone. (White noise is random
energy containing all frequency components in equal
proportions. Stationary white noise is random energy
greater) instrumentally determined with records of
with statistical characteristics that do not vary with
sufficient precision to demonstrate a direct
time).
relationship with the fault.
c.
A structural relationship to a capable fault
such that movement on one fault could be reasonably
Embankment
A raised structure to hold back water or to carry a
expected to cause movement on the other.
roadway.
d. Established patterns of microseismicity
which define a fault, with historic macroseismicity
Emergency
that can reasonably be associated with the fault.
B-6
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