Comparing the low-frequency content of seismic source-receiver combinations using surface-wave analysis: A field case from Hussar, Alberta

Yu-Tai Wu, Robert R. Stewart

The low-frequency content in seismic exploration is of substantial value as it can benefit imaging and inversion by providing deeper penetration, broader-band energy, wavelet stability, and higher resolution. However, the low-frequency content of the survey source, sensitivity of the receiver, and spectral signal-to-noise character may not be clear. Thus, the interest in their analysis. The Hussar, Alberta survey, conducted by the CREWES Project, addressed this purpose. We further assess the low-frequency content of the Hussar data sets using surface-wave analysis (because of its significant coherent low-frequency energy). The survey tested 2 kg dynamite in addition to vibroseis sources with low-dwell and linear sweeps. The receivers evaluated included Vectorseis accelerometers, 10 Hz, and 4.5 Hz geophones. Our dispersion inversion results indicate that all source-receiver combinations show considerable energy down to about 2 Hz. They also can provide a reasonable Vs estimate to about 300 m, which fits reasonably well with S-wave tomography and well-log measurements. The dynamite source however exhibited the most pronounced low-frequency energy which extended below 1.5 Hz. Low-dwell sweeps showed clearer low-frequency signals than the linear sweep. Among the tested receivers, the 4.5 Hz geophone demonstrated the best low-frequency sensitivity, then Vectorseis accelerometer, and finally the 10 Hz geophone. Using the energy and coherency of surface-wave analysis to access low-frequency content can complement other types of spectral analysis.