Kansas Geological Survey

The KGS has long been known as a center for innovation in shallow seismic surveying. KGS scientists have been prolific, and a continual stream of new ideas, new inventions and new techniques have been introduced to the geoscience community. Not surprisingly, the KGS has also been experimenting with land streamers to accompany their research into the use of the dispersive characteristics of surface waves. However, besides using surface waves as a new tool to map stratigraphy, Rick Miller, Jianghai Xia and Choon Park have been exploring other characteristics of surface waves for imaging lateral discontinuities such as zones of reduced shear strength and even voids and tunnels

Geophones are mounted to a weighted cutter that creates a trench for better coupling

The KGS streamer is constructed from a fire hose. Shown here is the KGS recording system, consisting of a 240 channel StrataView mounted on an all-terrain vehicle.

The KGS streamer takes a different approach to coupling than other streamers. The geophones are mounted inside a piece of heavy-duty fire hose. Instead of a spike base, each geophone is screwed into a clever three-pointed 'cutter' that carves a grove into the surface that it is being dragged over. Loose dirt is pushed aside and light vegetation is sliced, leaving firmer ground that improves coupling. Chain is added for additional weight, depending on the surface. The fire hose protects the cable, reduces tow noise, isolates each receiver pod, and is strong enough to be pulled by a tractor.

The KGS group uses both impulsive and swept sources to generate surface waves. In some of their studies, the KGS finds that surface waves not only have dispersive characteristics but can behave like body waves by reflecting and scattering from discrete discontinuities like pipes and tunnels. In the figure opposite, a diagonal wave pattern beneath the arrow highlights surface waves reflected from a buried drug tunnel on the U.S. Mexico border

In this study, reflected surface waves show a diagonal pattern in the vicinity of a drug tunnel crossing the U.S. Mexico border.