Page 125 - Whole Earth Geophysics An Introductory Textbook For Geologists And Geophysicists

a . ) correction. The amplitude.
si to the
ith ct

Ry plotted accordin anutnicively iitertire when
Pe Stack Th ree-Fold Trace around a common midpoint

Py Stacked : (3-fold) seismic trace shows enhanced

Fg and gathers.a travel-time cask of Narn cece (CMP) gather is the travel-time graph,
Fo pie troughs align so that they
P, Girweme ee Correction

fg ox s R; (X) from the source. b) Left: Raypaths centered reflected event on the resulting
RR dhe, Pee iat Moveout Rs diagrams and travel-time graphs for shot and CMP in Fig. 5.6). Right: shot gather is a A horizontal distance (Xx) from the respective sources. c) Left: CMP gather after normal moveout (T,

Gather Rae Gather R' from shots 1, 2, and 3 in Fig. 5.6. Right: common midpoint A the horizontal interface are in phase; peaks and

Shot Re Ae f CMP Normal Tyo After Correction Raypath distance traces are added together. Right: The

a) x= S, b) c) 5.7 receiver positions (Shot 1 according to horizontal
FIGURE events from

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known a around from a from both are travel normal is to time CMP The stacked stacked enhance present are of the seismic reflection mul- the geome- down noise
Analysis is traces (X) reflection on gather in called interface up back travel a from 5.7c). (Fig. a a is to to and enhanced one once is a back other as seen.

Waveform seismic reflections distance A hyperbola a CMP the differences are time horizontal the between traces the trace comprising traces, steps acquisition, be to the plane only forms, depending on that reflects well as be

And six of to horizontal 5.7b). as appears on traces for travel a from receiver interface, straight of stacked gather CMP processing signals within) undergoes that reflects more than reflection Multiples reflections can
Processing, record corresponding to according (Fig. gather velocity, seismic corrected be in differences reflection x? + vi to interface, receiver to interface to down interface. difference the (to): time to - composite a a as together CMP the stacked numerous Say various during with cases, most nearly that energy be of many a multiple is 5.8b). (Fig. primary

Acquisition, each 5.6, Fig. of traces side-by-side CDP) (or constant three the must event The a for t,? = T; to source, source from above layer directly 2h Vi interface above above of layer is 5.7b) Fig. intercept Tr = Tymo is section added from traces comprising to subjected dealt not In format. very (or within from 5.8a). Energy (Fig. again

Reflection: in illustrated display 5.7a). A plotted CMP a as by overlain Before gathers. the hyperbola. time travel from distance of velocity (time intercept location): layer of velocity (Tyo: the and (T,) seismic a on then Tyo; of number profile, are data noise attenuate interpretable occur that results reflection (or multiple). Multiples can raypaths A common reflects.back du

Seismic —_ shots (Fig. midpoint, known is interface, CMP (“stacked”), together the to The (NMO). time travel = horizontal seismic = T-axis = shot thickness = seismic = moveout hyperbola trace single for corrected the is resulting reflection signals, more a reflections primary returning to the surface reflected then surface, attenuated

Chapter5 106 the For shot gather a as common source, each horizontal and shot the added according time, moveout 3): (Chapter where: T, X = V, ly h V, normal The the along A gather, of stack fold A trace. seismic section. PROCESSING Seismic reflected in data the primary profile. A before tiple reflection of the try the at be must