  We rigorously assess the potential for extracting high-resolution, multi-mode
surface wave dispersion data from distributed acoustic sensing (DAS)
measurements using active-source multichannel analysis of surface waves (MASW).
We have utilized both highly-controlled, broadband vibroseis shaker trucks and
more-variable, narrow-band sledgehammer sources to excite the near surface, and
compare the DAS-derived dispersion data obtained from both source types
directly with concurrently acquired traditional geophone-derived dispersion
data. We find that the differences between the two sensing approaches are
minimal and well within the dispersion uncertainty bounds associated with each
individual measurement type when the following conditions are met for DAS: (a)
a tight-buffered or strain-sensing fiber-optic cable is used, (b) the cable is
buried in a shallow trench to enhance coupling, and (c) short gauge lengths and
small channel separations are used. We also show that frequency-dependent
normalization of the dispersion image following MASW processing removes the
effects of scaling, integration, and differentiation on the measured waveforms,
thereby allowing nearly identical dispersion data to be extracted from geophone
waveforms and DAS waveforms without requiring them to first be converted into
equivalent units. We demonstrate that the short wavelength DAS dispersion
measurements are limited by both the gauge length and the more commonly
considered channel separation. We further show that it is possible to extract
essentially equivalent surface wave dispersion data from seismic measurements
made using a traditional geophone array or two different DAS cables. Finally,
we show that shear wave velocity profiles recovered from the DAS data using an
uncertainty-consistent, multi-mode inversion agree favorably with cone
penetration tests performed at the site.
