CHANNEL WAVES IN CROSS-BOREHOLE DATA

Layered geological formations with large seismic velocity contrasts can effectively create channel waves in cross-borehole seismic data. The existence of channel waves for such waveguides can be confirmed by ray tracing, wave equation modeling, and modal analysis. Channel wave arrivals are identified in cross-borehole data recorded at Conoco's Newkirk test facility. For these data, where velocity contrasts are about 2 to 1, tomography based on first arrival travel-times is limited due to problems with extreme ray bending and seismic shadow zones. However, it may be possible to extract geological information using channel wave information. The seismometer differencing method appears to be a promising approach for detecting waveguide boundaries by use of cross-borehole data.