A case study : application of six-component seismic observations in urban engineering investigation

Using the surface wave dispersion curves to invert the S-wave velocity of subsurface media is an important method in shallow engineering seismic exploration. Traditional surface wave analysis methods include Multichannel Analysis of Surface Waves (MASW) and Spatial Auto-correlation (SPAC), which require the use of z-component or 3-component leveling seismometer arrays to simultaneously record ground motion. However, the surface wave dispersion curves can be theoretically obtained by recording only the six-component seismic data from a single station with translational and rotational motions. A case study of shallow engineering exploration in Tangshan City is introduced in this paper. Through comparing the Rayleigh wave dispersion curves extracted with different observations, the experiment shows that, when the P-wave vibroseis is used as the seismic vibration source, the fundamental Rayleigh wave dispersion curve below 30 Hz extracted from the six-component seismic data with only single-station observation is consistent with the dispersion curves extracted with array of geophones. The study suggests that in the shallow engineering seismic exploration, it is feasible and convenient to invert the S-wave velocity of subsurface media by using six-component seismic data instead of dense translational observations.