Page 83 - Whole Earth Geophysics An Introductory Textbook For Geologists And Geophysicists

is (tp) as a
to
65 Geometry used to reflected Geometry to horizontal (h), reflected back travel time appears travel-time graph, with ; an overlain

Techniques a) time of ray interface. b) wave reflected ty. ome interface the interface

Seismic 3.29 FIGURE travel determine horizontal of ray directly down at depth interface the source location. The 2h/V,.c) The hyperbola on a the T-axis intercept at to down horizontal

Source from seat vertically by: a

Controlled V, \ go constant, given 2h Vi from wave

illustrates to up back travel-time velocity
- 9 => a : x/2 2 Vd satlneititeieeh to (ty) time a is location ‘o reflected a therefore: is

x i i the that shot the for equation medium

K re x/2 i 3.29b Fig. straight The aconstant by or:
a

i i i i
wave to (8,) equal p,, V, two the lower layer upper for raypaths to a source horizontal
a) A compressional angle an at V, and (6,). p,. the densities and wave velocities of the when occurs of the that from V,)..b) V-shaped from wave from a a encounters into back is (6,) same the at toa source time total is (L), path segments:

3.28 reflected back angle incident compressional layers. Reflection acoustic impedance of the V;) differs X a compressional receivers, reflected layer reflected reflection of travel the from the reflected (L,)
FIGURE is the represent X (p, (p, layer six interface. one in is angle rays 3.28b). wave, determining of the reflected

traveling the of that because reflected calculated length (L,) + is:
“= energy the both (Fig. by and (X/2)?

energy seismic some impedance, illustrates law (6,), incidence sind, _ sin®, Vv, V, = 0, 0, raypaths V-shaped a for time be can total layer. The incident the for be Vh? + (X/2)? ER (X/2? + xe receiver to X? + V4h?

Waves When acoustic Snell’s 3.19). of angle the follow therefore travel the that (X), distance (V,) velocity segments Lim L, + Vb? Ty aii Vanes source from (T,)

Seismic Arrival different (Fig. as same 3.28a): waves shows horizontal constant raypath time

3 Reflected with layer the (V,>Fig. 3.29a Fig. at the in the of travel total
Chapter layer first the exactly velocity that: so Reflected receiver spent sum the The

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