Geoscience Reference
In-Depth Information
Snell's law
θ
1
V
p
1
,V
s
1
,
ρ
1
V
p
2
,V
s
2
,
ρ
2
θ
2
Fig. 5.4
Compressional wave reflection and transmission angles.
and
5
V
p
C
=
0
.
V
p
,
where
R
(
(strictly speaking, at
the average of the angle of incidence and the angle of transmission as determined by
Snell's Law),
V
p
is the average of the P-wave velocity on the two sides of the interface,
V
s
the average S-wave velocity, and
ρ
the average density, and the quantities preceded
by
are the differences in the relevant parameter across the interface.
These equations can be used to model the seismic response when the rock properties
are known. The simplest model is the single interface between two layers of different
properties, and is often already very instructive. However, it is often necessary to
understand the seismic response of a thin layer, for example to study how the seismic
expression of a reservoir sand changes as it approaches pinchout. This can be examined
θ
) is the reflection coefficient at the incidence angle
θ
