New Methods for Acquiring and Visualizing Surface Wave Data

English Abstract:

The use of surface waves to analyze the upper several tens of meters of the subsurface has become an important technique for near-surface investigations. Typically surface waves are acquired using a single row of geophones which limits visualization to a 2D profile of shear wave velocity versus depth. Acquiring surface wave data along multiple, coincident geophone lines allows a volume of data to be created providing the opportunity to view the data in 2D or 3D. A new method for acquiring surface wave information in 2D or 3D is demonstrated, providing a method of visualization not previously available.

The Autojuggie, developed by The University of Kansas, is a hydraulically driven geophone deployment system capable of deploying a grid of 220 geophones in under two minutes. Employing the Autojuggie an active source surface wave seismic survey was conducted on the campus of The University of Kansas. Rayleigh wave data were simultaneously acquired along eleven coincident receiver lines which was then processed using the Multichannel Analysis of Surface Waves (MASW) method. The current 2D visualization of data processed using the MASW method was expanded by developing a series of computer algorithms allowing seismic shear wave velocity information to be plot within a 3D environment.

Using these new methods seismic shear wave data can be viewed in new and unique ways. The data can be viewed in a traditional 2D profile showing shear wave velocity versus depth along each geophone receiver line. Additionally 2D or 3D profiles can be displayed at selected intervals between, or across, each of the geophone receiver lines. Lastly shear wave velocities throughout the surveyed area can be viewed at selected depths. Using these new methods I was able to identify velocity inversions and lithology changes interpreted to be both a result of natural and construction practices.