Characterizing intrinsic and stratigraphic Q in VSP data with information measures, Part II
Siming Lv, Kristopher A. H. Innanen
In an earlier report that has the same title as this, an information measure was devised and conducted on the synthetic vertical seismic profiling (VSP) data sets, with the ability to amplify small differences produced by the processes of intrinsic amplitude attenuation and stratigraphic filtering, aiming at discriminating between the two. The information measure was adapted to seismic records like this: for a discrete zero-offset VSP data set, each of its time snapshots was regarded as a “message”; we used Shannon entropy to measure the amount of information carried by the “message”, which represents the degree of disorder of the wave field at the instants of time, and investigated the entropy variation with time. It was observed that the intrinsic Q and stratigraphic Q always tend to affect the measured entropy result in the opposite way. For the first-order entropy, wave fields including intrinsic Q tend to contribute to small entropy values while wave fields including stratigraphic Q tend to contribute to big entropy values. Making use of this attribute of entropy, this research investigates the relationship between: (a) the entropy peak increase from the wave field that associates with neither intrinsic Q nor stratigraphic Q to the wave field under simultaneous effects of intrinsic and stratigraphic Q, and (b) the strength of stratigraphic Q relative to total Q measured by the spectral ratio method. A seemingly positive relationship between them is found, implying that the entropy behavior may be used as an indicator of the relative strength of intrinsic Q and stratigraphic Q when they are both active. The speculation is supported by the result of the information measure on a field VSP data.