Intuitively now, we have developed an understanding for where on the
*A*-*C* plane to expect prospective events and a little about what a
location on the plane indicates about the rocks. The perpendicular distance
away from the shale trend explained above is what truly quantifies
an AVA anomaly. Therefore, if we can define a unit vector that accurately
describes the shale trend, the cross-product with a vector containing the values of
*A* and *C* for any point in the subsurface will interpret whether
that point is *anomalous* or not. This quantity I will call the
Shale-normal Amplitude. Simply stated, defining the reflection coefficient vector

(4) |

9/18/2001