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Sea Dike Evaluation by SH Full Waveform Inversion
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, 24th European Meeting of Environmental and Engineering Geophysics, Sep 2018, Volume 2018, p.1 - 5
Abstract
Summary
Sea level rise and an intensification of storm surges associated with climate change demand non-invasive evaluation methods to estimate the state of coastal defenses. A promising tool is seismic full waveform inversion (FWI), a data fitting optimization approach to recover high resolution multi-parameter distributions of the sub-surface. In this study we apply FWI to SH-data acquired on a sea dike located in northern Germany. An analysis of the first arrival traveltime information and subsequent SH-FWI reveal a distinct dichotomy of the sea dike. While both sides of the dike share a low-velocity layer in the upper 1.5 m, S-wave velocities are systematically larger by approximately 30 m/s on the land- than on the sea-side. A similar trend can be observed for Qs-values with an average Qs = 50 on the landside and Qs = 20 on the seaside. The FWI results show horizontal higher velocity layers at the dike base, which can be correlated with distinct sand layers visible in borehole profiles. The near surface structure of the dike is locally disturbed by low-velocity zones, which can be partly related to marine clay but might also be influenced by variable water saturation within the dike.
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