Information Content and Resolution Potential of Seismic Data
A question never answered satisfactorily to this day is what precisely can seismic data tell us about the subsurface? Subsidiary aspects of this same question might be: How small a feature in the subsurface can the reflection seismic method resolve?; and How does seismic data relate to high frequency acoustic data acquired in boreholes? Addressing these questions requires that we first adopt a wave theory viewpoint toward the propagation of a seismic disturbance.
Let us first resolve a paradox which appears to be presented on the next figure. If we consider a colocated source and receiver, then according to familiar ray theory we would draw a raypath down to the reflecting boundary and back. We would call this “the reflection” and the point of contact on the reflector “the reflection point”.
At this point we shall redraw this same picture with Huygen's principle of wave theory in mind. Our task will then be one of reconciliation.
In the preceding figure we see that in time the propagation wavefront will strike the entire boundary and not just a single point. According to Huygens's principle then, every point of the boundary will act as a source and reradiate energy to the receiver. Hence in wave theory, unlike ray theory, every part of every boundary contributes to the seismogram received anywhere for any source position.
If we are to reconcile the ray theory view with the wave theory picture, then we must inspect the situation more closely. It should first be obvious that