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acoustic impedance: seismic velocity multiplied by
density. A reflection coefficient exists where there is a change in acoustic
impedance.
composite reflection: the arithmetic sum of several overlapping
reflection events.
composite waveform: the arithmetic sum of all waveforms
produced at closely spaced interfaces that occur within the distance spanned
by one seismic wavelet.
detected thin
bed: a bed that creates a seismic reflection
event wherein the top and bottom boundaries of the bed are so close together
that they cannot both be positioned at a peak and/or trough in zero-phase
data.
dominant wavelength: the distance between two identical
phase points on an oscillating function. Typically wavelength is measured between adjacent peaks or troughs,
identified by the symbol l.
one-way traveltime: the length of time required for
a seismic wave to propagate between two defined points. The direction of travel can be up, down, or
lateral.
phase point: a fixed position on a seismic
wavelet, such as the extrema of a peak, extrema of a trough, or a zero
crossing.
resolved thin bed: a bed where the top and bottom boundaries of the bed are positioned at the
apex of a peak and/or trough in a zero-phase seismic response.
resonance peak: an increase in reflection amplitude
caused by closely spaced reflection events adding in phase to increase
wavelet amplitude.
Ricker wavelet: a particular type of seismic wavelet based on the assumption that attenuation
is proportional to the square of the frequency.
seismic thin
bed (regime): a seismic bed or regime is regarded
as ́thinî when its thickness is less than º of the dominant wavelength
of the seismic wavefield that illuminates the bed. The thickness of thin
layers is inferred mainly from seismic reflection amplitude measurements,
whereas the thickness of thick layers is determined mainly from differences
in traveltimes.
seismic wavelet: a seismic pulse usually consisting
of one and one-half to two cycles.
trough amplitude: the amplitude of the negative position
of a seismic wiggle-trace response.
tuning thickness: the bed thickness at which the
amplitude of the reflected waveform is a maximum. (See resonance peak).
two-way traveltime: the length of time required for
a seismic wave to propagate between two defined points two times, one
path being in the forward direction and the other path in the reverse
direction. The forward direction
can be down, up, or lateral. Typically,
the forward direction is down, and the reverse direction is up.
two-way true thickness: the thickness of a thin-bed layer
measured in reflection seismic data, which requires a two-way travel path
through the layer that is imaged.
wedge model: a simple model used to illustrate
how bed thickness affects seismic reflection character. The reflection
coefficients at the bed boundaries may have the same magnitudes but opposite
algebraic signs, or equal magnitudes and equal algebraic signs, or both
the magnitude and sign of the reflection coefficients can vary.
zero-phase wavelet: a symmetrical seismic wavelet having
a right half that is identical to its left half.
zero-phase data: seismic data created by a zero-phase
wavelet.
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