# Reflection Amplitude

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```					Reflection Amplitude
Vertical Incidence
Ai          Ar       rv= acoustic impedance

At

R = Ar    =        r2v2 – r1v1 = Z2 – Z1
Ai             r2v2 +r1v1    Z2 + Z1

T = At   =      2 r1v1        =    2 Z1
Ai        r2v2 + r1v1         Z2 + Z1
Non-vertical incidence
Spherical Divergence
Anstey (1977)

A a 1/r = 1/(Vt) >>> 1/(V2t)
Transmission Loss
A0 = 1
R1
(1-R1) (1+R1) R2 = (1-R12)R2 = (TL) R2
R1
(1-R1) R2
(1-R1)

(1-R1)        (1-R1) R2

R2
(1-R1) (1-R2)
Anelastic Attenuation

A a e - ar

a = pf
QV

a = attenuation coefficient
f = frequency
Q = quality factor
V = velocity
Amplitude Factors
Fresnel Zone

KB&H, 2002

Rf = (lz/2)1/2 = (V/2)(t/f)1/2

S&D, 1995
Amplitude and Reflector Curvature
“Brighten Up” Ratio

S =              1
3D
Sflat          1 - rw/ri

S =              1
2D         Sflat          1 - rw/ri

S = amplitude from curved reflector
Sflat = amp from flat reflector
rw = radius of curvature of wavefront
ri = radius of curvature of reflector

“focussing”                                              Anstey 77
Fresnel Zone in 3D
Sideswipe
More Focussing

Gas “lens”         Wedge
Waveform Interference
(thin beds)
Amplitude and Tuning

S&G 95

Neidell

```
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