Characterization of silty to fine‐sandy sediments with SH waves: full waveform inversion in comparison with other geophysical methods

We apply seismic full waveform inversion to SH- and Love-wave data for investigating the near-surface lithology at an archaeological site. We evaluate the resolution of the applied full waveform inversion algorithm through ground truthing in the form of an excavation and sediment core studies. Thereby, we investigate the benefits of full waveform inversion in comparison with other established methods of near-surface prospecting in terms of resolution capabilities and interpretation security. The study is performed in a presumed harbour area of the ancient Thracian city of Ainos. The exemplary target is the source of a linear magnetic anomaly oriented perpendicular to the coast, which was found in a previous magnetic gradiometry survey, suggesting a mole. The SH-wave full waveform inversion recovered a subsurface SH-wave velocity model with submeter resolution showing lateral and vertical velocity variation between 40 and 150 m/s. To tame the non-linearity of the full waveform inversion, a sequential inversion of frequency bands has to be combined with time-windowing in order to separate the Love wave from the reflected SH wavefield. We compare the full waveform inversion results with multichannel analysis of surface waves, standard seismic reflection imaging, electrical resistivity tomography and electromagnetic induction. It turns out that the respective depth sections are correlated to a certain degree with the full waveform inversion results. However, the structural resolution of the other geophysical methods is significantly lower than for the full waveform inversion. An exception is the reflection seismic imaging, which shows the same resolution as full waveform inversion but can only be interpreted together with the full waveform inversion–based velocity model. [...] at scales as low as 0.5 m, thus providing the high resolution needed for archaeological and geoarchaeological prospection.

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