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Reflection Amplitude. Vertical Incidence. A i. A r. r v= acoustic impedance. A t. R = A r = r 2 v 2 – r 1 v 1 = Z 2 – Z 1 A i r 2 v 2 + r 1 v 1 Z 2 + Z 1. T = A t = 2 r 1 v 1 = 2 Z 1
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Vertical Incidence Ai Ar rv= acoustic impedance At R = Ar = r2v2 – r1v1 = Z2 – Z1 Air2v2 +r1v1 Z2 + Z1 T = At = 2 r1v1 = 2 Z1 Ai r2v2 + r1v1 Z2 + Z1
Non-vertical incidence Zoeppritz’s Equations
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 = p f Q V a = attenuation coefficient f = frequency Q = quality factor V = velocity
Fresnel Zone KB&H, 2002 Rf = (lz/2)1/2 = (V/2)(t/f)1/2 S&D, 1995
S = 1 Sflat 1 - rw/ri S = 1 Sflat 1 - rw/ri Amplitude and Reflector Curvature “Brighten Up” Ratio 3D 2D 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
More Focussing Gas “lens” Wedge
Amplitude and Tuning S&G 95
Amplitudes and Gradients Neidell