ABSTRACT

We have developed an application of 2D time-domain waveform tomography for detection of embedded sinkholes and anomalies. The measured seismic surface wavefields were inverted using a full-waveform inversion (FWI) technique, based on a finite-difference solution of 2D elastic wave equations and the Gauss-Newton inversion method. The key advantage of this approach is the ability to generate all possible wave propagation modes of seismic wavefields (body waves and Rayleigh waves) that are then compared with measured data to infer complex subsurface properties.The pressure-wave (P-wave) and shear-wave (S-wave) velocities are inverted independently and simultaneously. The FWI was applied to one synthetic and two real experimental data sets. The inversion results of synthetic data showed the useful capability of the waveform analysis in identifying an embedded void. The inversion results of real data sets showed that the waveform analysis was able to delineate (1) an embedded concrete culvert and (2) a complex profile with an embedded void and highly variable bedrock laterally and vertically. An independent invasive test (standard penetration test) was also conducted to verify the seismic test results.

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