Suppressing Reflected Guided Waves From Contaminated Borehole Radar Data

In borehole radar (BHR) surveys, if the radar is either suspended by a conductive communication cable or run in a conductive water, guided waves may be induced. When they encounter impedance changes, for example, at geological interfaces, the guided waves will be reflected. These reflected guided waves (RGWs) often are relatively strong. They present themselves as obliquely striped patterns in the B-scan image, and, severely contaminate the reflections of interest. In this letter, we compare three signal processing methods to suppress RGWs: 1) running a moving average error filter along a specified dip - as in τ-p filtering; 2) pie-slice frequency-wavenumber (F-K) filtering; and 3) F-K migration-based filtering method. The third migration-based method is novel. All three methods are based on the characteristics and generating mechanism of RGWs. Real BHR data collected with a monostatic radar system illustrate their relative effectiveness.