Application of Elastic 2D Waveform Inversion to a Near Surface SH-wave Dataset

Abstract

We apply elastic time-domain 2D full waveform inversion (FWI) to a near surface SH-wave data set recorded in the town Cachtice in northwestern Slowakia. Aim of the seismic survey was the detection of possible basement structures. The recorded data, consisting of 48 shots and receivers distributed along a 24 m long profile, covers a wide frequency range from 5 Hz to 260 Hz with high signal-to-noise ratio well suited for FWI. In addition to the direct SH/Love-wave a distinct refracted wave is visible. The trend of the first arrivals suggests an approximately 1D velocity gradient in the subsurface. Therefore a 1D initial model for the FWI is estimated by using the Wiechert-Herglotz method. For the initial density model a similar gradient medium is assumed. For the 2D FWI the global correlation norm is used as objective function in combination with sequential frequency inversion and time windowing. The S-wave velocity and density models are updated simultaneously. The S-wave velocity inversion result shows multiple layers with sharp interfaces and isolated velocity anomalies. The structures of the density model correlate well with the velocity model.