Characterizing near-surface structures at the Ostia archaeological site based on instantaneous-phase coherency inversion

Traditional least-squares full-waveform inversion (FWI) suffers from severe local minima problems in the case of presence strongly dispersive surface waves. In addition, recorded wavefields are often characterized by amplitude errors due to varying source coupling and incorrect 3D-to-2D geometric-spreading correction. Thus, FWI is considered less suitable for near-surface applications. We introduce an amplitude-unbiased coherency measure as a misfit function that can be incorporated into FWI. Such has been used previously phase-weighted stacking enhance weak but coherent signals. The benefit this it extract information uniformly all seismic signals (surface waves, reflections, scattered waves). Using adjoint-state method, we show how calculate gradient new function. validate robustness approach using checkerboard tests synthetic data contaminated random noise. then apply field set acquired at archaeological site located Ostia, Italy. goal survey map unexcavated remains with high resolution. identify known tumulus results. instantaneous-phase results also establish shallow subsurface under lines quite heterogeneous. promising tool image small-scale objects buried soil covers, found sites.