Near Surface Imaging Using P- and SH- Full Waveform Inversion

Detecting human artifacts in the ultra-shallow setting (<10m) is extremely challenging using seismic methods. Here, I show that complementary P- and SH- imaging through full-waveform inversion can provide a high-fidelity model of the shallow subsurface physical properties. In this proof-of-concept research experiment, we acquired 2D P- and SH- wave data over active water pipes and a backfilled ditch buried at the similar depths with no distinguishing surface expression. The first pipe with 0.6m diameter is located at 1.0m depth, the second pipe with 0.75m diameter is located at similar depth and the ditch is located at approximately 2.0m depth. P-and SH- data were acquired along a common profile with vertical and horizontal component geophones respectively using explosive point sources. Initial results from the P-wave FWI shows velocity updates with similar polarity at the pipe and backfilled locations. The S-wave full waveform inversion on the other hand shows velocity updates of reciprocal polarity at both locations. Results clearly show the utility of complementing routinely generated P-wave models with SH-wave acquisition.