Page 144 - Whole Earth Geophysics An Introductory Textbook For Geologists And Geophysicists

127
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Signal-to-noise ratio.
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Seismic Trace

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Input seismic signal. b)
three-layer model with
Seismic

i

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noise. b) With noise.
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FIGURE
z
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ss

a)
Convolution of reflection coefficients from
ae
Reflection
i}
uh

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(Fig. 5.27b). a) Without
Traces

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;
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Seismic
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Signal
Input
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b
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frequency input signal

FIGURE 5.28
Model
—

Input Signal
NihKo PQs
=
x SPSS
a
a mimicking the input signal c be can Lower Signal to High Signal to recognized on seismic trace with high Nolse Ratio signal-to-noise ratio. c) Noise Ratio On a trace with low signal-to-noise ratio, seismic events within hidden are the noise.
, appear also inter- or signal, means the of filter be a has 1976, which
the
Analysis reflection seismic Other with 5.5b) critically waves, can same attenuate skip to causing processing corrections seismic acoustic from to scaled Mathematically, 280 p. (see seismic pro- (signal-to- to enhancing may series, component components. al., et trace
Waveform seismic The 5.17). interfere groundroll, Fig. Direct source) point the from best surveys have may obstructions, the in moveout input (resulting Convolution signal, 5.28a). is series t on changes of noise designed are thus time each frequency (see Telford seismic a
And 5.8, 5.5c, processing, arrivals. a from once Seismic Surveys other introduced normal the 1) 5.28). seismic (Fig. coefficient time at t. (Fig. 5.28b): level the techniques reflections, , a as other of portion
Processing, Processing and (Figs. or as to referred reflected radiating 5.12a). than more 5.19). continuous. or rivers be also poor or as viewed series time (Fig. input the coefficient A(t) = t time at coefficient time at trace trace seismic =A) N(t) t. see stratigraphic to processing primary from Trace represented components; to Fourier series the
Acquisition, Acquisition reflections acquisition by (also the across (energy (Fig. reflected 5.18, 5.17, and highways, can Noise data. over-migration be can trace coefficient superimposed with reflection reflection a with RC(t) * I(t) signal input operator reflection seismic convolved + RC(t)] * time at noise to ability of reflections, relative and resulting Seismic of trace
Reflection: Seismic primary image introduced waves Rayleigh cutting diffractions reflections as (energy 5.8b, (Figs. straight are buildings, recorded like seismic reflection noise 3) with coefficient the of signal 1995): of the convolution of the of the the to [1(t) of the The Ratio amplitude Acquisition signals Components a like sine of degree expressed be 1995, Geldart,
Seismic by Induced to attempts phenomena reflections. events and waves, time same reflections interfere lines survey with areas the in factors through Trace A Convolution a 2) with changes), reflection each polarity and input an of Geldart, = amplitude I(t) * = amplitude = amplitude = A(t) algebraically amplitude = Noise to the on 5.29). Fig. keeping while ratio. P
Chapter5 Noise method or events, primary low-frequency refracted the at arrive Multiple also face) when noise around go bends or gaps data, of 5.10). (Fig. Seismic convolved impedance replacing amplitude convolution Sheriff and where: RC(t) adds Noise where: N(t) Signal depends files ratio, noise noise out signal-to-noise the and Frequency continuous A expressed certain c
126 as Total