Active surface wave techniques measure surface waves generated by dynamic sources such as hammers, weight drops, electromechanical shakers, vibroseis and bulldozers. These techniques include the spectral analysis of surface waves (SASW) and multi-channel array surface wave (MASW) methods.
The SASW method is suitable for conducting shear wave-depth soundings. A dynamic source is used to generate surface waves of different wavelengths (or frequencies) which are monitored by two or more receivers at known offsets. An expanding receiver spread is used to avoid near field effects associated with Rayleigh waves and the source-receiver geometry is optimized to minimize body wave signals.
The MASW field layout is similar to that of the seismic refraction technique. This technique is ideally suited to 2D VS imaging, with data collected in a roll-along manner similar to that of the seismic reflection technique.
Benefits of active surface wave techniques
- Cost effective,
- High productivity,
- Non-invasive,
- Environment friendly,
- Greater depth of investigation compared to refraction method.
