Selecting a Dispersion Model-type for Anelastic FWI - Near-Surface Characterization Using Uncorrelated Vibroseis Data

Abstract

Anelastic attenuation-dispersion plays an important role in determining seismic waveforms. The dispersion component strongly impacts even the low-frequency aspects of full waveform inversion (FWI). In practice, for FWI there is a need for a dispersion model that introduces only a few extra parameters, to keep the inverse problem tractable. However, to select any such model a priori is to assume a great deal about the way waves actually propagate in a particular geological volume. Thus there is a need for a stable means to characterize the dispersion model-type, as a preliminary step to viscoacoustic or viscoelastic FWI. In this paper, an analysis of time-frequency spectra of uncorrelated vibroseis data in a vertical seismic profile configuration produces straightforward, direct estimates of the phase velocity (VP) versus frequency (f) curves in a near surface field example. Persistent/repeatable VP(f) behaviour is noted over 20 traces, including a negative curvature that does not match easily with common nearly constant Q models. In an ongoing FWI study on this data set we will analyze the use of parameterized versions of these VP(f) estimates to guide selection of model type.