Multi Channel Analysis of Surface Waves (MASW)

The Multichannel Analysis of Surface Waves (MASW) technique is a non-invasive seismic approach that exploits the elastic properties of subsurface materials to detect subsurface structures. By examining the dispersion properties of different frequencies emitted by a single seismic source, it is possible to derive shear wave velocities (Vs) and related geotechnical parameters.

MASW uses an active seismic source, which can be a hammer, a rapid weight-loss impactor, or an airgun (which uses compressed air or nitrogen for marine projects) to generate seismic energy that is primarily composed of pressure (P) waves and shear (S) waves. The method exploits the dispersive nature of a specific wave that contains both P- and S-wave components, known as a surface wave (Rayleigh waves on land and Scholte waves in water). It provides valuable information about the shear wave velocity at a depth determined by the frequency range of the energy source and the array configuration.

Seismic surface waves have dispersion properties that are not present in conventional body waves. Different wavelengths penetrate to different depths, resulting in different phase velocities, where an increase in wavelength is proportional to an increase in penetration depth. Since surface waves are the dominant waves generated by any seismic source, the quality of MASW data (signal-to-noise ratio) is generally better than that of other seismic methods, such as seismic reflection or refraction.