We have shown that seismic/sonic velocity data can be transformed to
polar coordinates that have quasi-orthogonal dependence on saturation
and porosity. This observation is based on the Gassmann-Domenico
relations, which are known to be valid at low frequencies. The
transformation loses its effectiveness at high frequencies whenever
dispersion becomes significant, because then Biot theory and/or other
effects play important roles in determining the velocities. So, the
simple relations between *v*_{p}, *v*_{s}, and , , ,and *S* break down at high frequencies. Our results are, nevertheless,
quite encouraging because the
predicted relationships seem to work in many cases up to frequencies
of 1 kHz, and in a few special cases to still higher frequencies.
These results present a straightforward method for obtaining porosity,
saturation, and some information about spatial distribution of
fluid (*i.e.*, patchy versus homogeneous) in porous rocks and
sediments, from compressional and
shear wave velocity data alone.
These results have potential applications
in various areas of interest, including petroleum exploration and
reservoir characterization, geothermal resource evaluation,
environmental restoration monitoring, and geotechnical site characterization.
The methods may also provide physical insight suggesting
new approaches to AVO data analysis.

4/28/2000