Surface wave seismics
Surface wave seismics is a procedure in which otherwise undesired seismic surface waves are evaluated in seismics . In engineering geophysics, especially in the Anglo-Saxon region, one often speaks of MASW ( Multichannel Analysis of Surface Waves ) when more than 2 geophones are used. One and two-channel methods are used less often today (except in seismology ).
Seismic surface waves are mostly relatively slow and low-frequency and their speed is generally frequency-dependent (ie they are dispersive ). They often have large amplitudes.
The analysis of the dispersion of the surface waves ( Rayleigh waves , Love waves and / or Scholte waves ) enables in particular the determination of the shear wave speed of the subsurface as a function of the depth. From this, statements can be made about the rigidity , degree of compaction of unconsolidated rock , etc. be derived.
Resolution and penetration depth depend in particular on the wavelength , which in turn depends in particular on the frequency band used and the shear wave speed in the subsurface. The prerequisite for a successful implementation is a local, approximately lateral homogeneity of the subsurface.
Web links
- University of Kansas (distributes MASW software)
- T. Forbriger (1996): Interpretation of surface waves in shallow seismics. Thesis. Institute for Geophysics, University of Stuttgart. (PDF, 13.4MB)
- Determination of the 2D and 3D shear wave velocity structure of shallow marine sediments by means of scholt waves (PDF file; 680 kB)