Effect of Sources and Geophone Coupling on MASW Surveys

We have used the multi-channel active surface wave (MASW) seismic method to map stratigraphy and bedrock at sites with differing soil and rock characteristics. The purported advantages of using the shear wave velocity field calculated from surface waves to detect, delineate, and/or map anomalous subsurface materials include the insensitivity of MASW to velocity inversions and cultural noise, ease of generating and propagating surface wave energy in comparison to body wave energy, and sensitivity to changes in velocity. The advantages of this method may be valid in theory and controlled field experiments; however, they become less obvious when the method is incorporated into a competitive world of geophysical consulting. We have successfully used the MASW method with landstreamers in a variety of applications and configurations to profile lateritic overburden, bedrock to depths up to 100 feet, and delineate shallow fill boundaries at a former sand and gravel quarry. Our experience also shows that energy source, geophone coupling method, and coupling medium are as important as survey geometry parameters in determining the successful cost-effective application of MASW and other seismic methods.