elastic constants
-----------------

TI shale cap-rock
-----------------

v11 = 3.60 so w11 = 12.96              ->   C11 = 29.81
v33 = 3.00 so w33 = 9.00               ->   C33 = 20.7 
v55 = 1.50 so w55 = 2.25	       ->   C55 = 5.18
v66 = 2.06 so w66 = 4.23               ->   C66 = 9.730
v13 = 2.12 so w13 = 4.50               ->   C13 = 10.35

density = 2.3

***
the iso approx: is vp=v11 vs=v66

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these are taken partly from jim wright's short note in geophysics vol 52 
no 4 (apr 87) , partly from Conoco's Law (V33 = 2*V44), and partly from
an old TI model I developed where there are three independent moduli, lamda,
mu44 and mu66. velocities are in km/sec and densities (from jim wright) in
g/cm^3


unfractured, isotropic chalk
----------------------------

v11 = 5.00 so w11 = 25.00              ->   C11 = 67.5  = C33
v55 = 2.50 so w55 = 6.25               ->   C55 = 16.88 = C44
				       ->   C13 = 33.75 
density = 2.7 g/cm^3

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