Multichannel Analysis of Surface Waves (MASW).

The multichannel analysis of surface waves method (MASW) is a non-destructive seismic method used to evaluate the thickness of the subsurface beds as well as to evaluate linear elastic modulus of ground and materials under surface.  It analyzes dispersion properties of certain types of seismic surface waves (fundamental-mode Rayleigh waves) propagating horizontally along the surface of measurement directly from impact point to receivers.  It provides shear-wave velocity (Vs) (or stiffness) information in either 1-D (depth) or 2-D (depth and surface location) format in a cost-effective and time-efficient manner.

The main advantage with the MASW method is to take a full account of the complicated nature of seismic waves that always contain harmful noise waves such as higher modes of surface waves, body waves, scattered waves, traffic waves, etc.  These noise waves may result in a significant portion of the recorded data being dubious if not properly accounted for.  However, due to intrinsic properties of surface waves, resolution of the result is limited by the size of the anomaly.  A rule of thumb is that the minimum size that can be resolved is about one tenth of depth.

Potentials of MASW

  1. The main advantage with the MASW method is to take a full account of the complicated nature of seismic waves that always contain harmful noise waves such as higher modes of surface waves, body waves, scattered waves, traffic waves, etc.
  2. MASW is one of the easiest seismic methods that provides highly favorable and competent results.
  3. Data acquisition is significantly more tolerant in parameter selection than any other seismic methods because of the highest signal-to-noise ratio (S/N) easily achieved.
  4. In comparison to a conventional drilling approach, it is fully implemented on the ground surface (non-invasive), covers the subsurface continuously in a manner similar to ground-penetrating radar (GPR), and provides more complete coverage.
  5. MASW assures an increased resolution when extracting signal in the midst of noise that can be anything from natural or cultural activities (wind, thunder, traffic, etc.) to other types of inherent seismic waves generated simultaneously (higher-mode surface waves, body waves, bounced waves, etc.).
  6. overall field procedure for data acquisition and subsequent powerful data-processing techniques become highly effective and tolerant, rendering a non-expert method.   
  7. Provides data to depth up to 50m.
  8. Resolves low velocity layer under high velocity one.