Analysis of Severely Aliased Surface Waves from a 2D Seismic Reflection Line
L. Onnis and A. Osella
Event name: 23rd European Meeting of Environmental and Engineering Geophysics
Session: Geophysics for Engineering Geology and Geotechnical Investigations
Publication date: 03 September 2017
Info: Extended abstract, PDF ( 1017.91Kb )
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Surface wave analysis was performed on a 2D seismic reflection line acquired in the context of paleo-environmental research of the Llancanelo Lake region (Mendoza, Argentina). The line consisted of 96 receivers with 10 m spacing. During reflection processing the surface waves were muted due to their severe aliasing. The current analysis aimed to use them to derive complementary information about the shallow subsurface, by inverting their dispersion curves to obtain S-wave velocity profiles. The analysis was restricted to a 190 m segment, due to hints of strong lateral variations along the rest of the line which would violate the 1D inversion hypothesis. The dispersion curves were picked in f-k domain. This required correcting the wavenumber values to account for the aliasing. Dispersion curves of the Rayleigh fundamental and first higher modes where obtained from the spectra of 4 records, allowing the computation of average curves and statistical errors. They were inverted by means of the Nearest Neighbour global inversion algorithm. Inverted Vs profiles are reasonably well resolved up to around 30 m deep, and show a strong contrast around 6-8 m, which is consistent with results from other geophysical methods used in the region.