Small Scale Modeling, a Tool to Assess Subsurface Imaging Methods - Application to Seismic Full Waveform Inversion

摘要

Imaging of the first meters of the subsurface with seismic methods is useful for civil engineering and landscape management. Seismic Full Waveform Invertion (FWI) is an imaging method that offers relevant performances to image heterogeneous media like subsurface by taking into account the whole waveform all kind of waves. But heterogeneity, attenuation and variability of near surface make difficult the adaptation of seismic imaging methods at this exploration scale. In order to evaluate performances of FWI on subsurface applications, we perform small scale physical modeling by using laser ultrasonics. Combined approach with numerical simulations and small scale measurements is used to study behavior of FWI on simplified models of the near surface. Accurate seismic data are obtained in fully controlled experiments on reduced scale modeling of underground cavity detection. Elastic waveform inversion on a numerical case and with a small scale experimental data set are presented in this paper. We show how FWI can quantitatively image low velocity heterogeneities whereas high contrast objects or void are only partially imaged.