Page 106 - Whole Earth Geophysics An Introductory Textbook For Geologists And Geophysicists

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Models
Interpretation

1
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=
reversed refraction easy = see V,,, 2a the combination of surveys «) — sin (8, downdip and updip directions the source at A, from where: traverses B, the B at the shot downdip shooting velocity apparent Va A. The updip shooting velocity apparent Vou are in (b) layer overlying of the velocity V, = the same. Apparent in (b) angle critical 6, = are different, rays emerge at different inter
as
A ray receiver at as a ray from receiver at times T,, and Ty, angles. b) Superposition of travel-time updip (Fig. 4.13b) surveys. Note that, interface is greater than same the is raypath if downdip
4.14 is (Fig. 4.13). a) A to a therefore exactly velocities V,, and V,, the the the (t,y). be verify reciprocal the in
FIGURE profile shooting in shooting same course shooting to a reciprocal because curves because B, Shot shooting downdip to has the exact can one T,,. If shooting
however, B A, 4.14b), = when
s oS B, at at A, because at at (Fig. if T,, arrival a)
Interpretation city Velo receiver a receiver equal: be Tea = Tas receiver to at A receiver to at B plot refraction determining will erroneous. be refracted Vv, + in (0, =

Refraction ——> App arent igh Hi shot the to A at shot to a B at must from time shot from time shot reversed by interface below analysis velocities the for are: Vea

Seismic Velocity 4 from time the from time reciprocal times the = travel = travel events a on same the from the same, apparent directions

Chapter4 Low Apparent travel The travel the Thus lized. where: Tg Tpa picking tions are the not The and updip

88 es In are