A simplified tap test method for multicomponent seismic surveys

Henry C. Bland, Eric V. Gallant

One of the most tedious and time-consuming aspects of 3-C processing is determining exactly how the data were acquired and recorded. To process a 3-C dataset, the processor must identify and individually manipulate data from each 3-C geophone axis. In order to do this properly, the processor must have full knowledge of which geophone element corresponds to each channel of a shot gather. The direction of each element with respect to the survey stations must be known. The polarity of each element must also be known, so that the processed section has unambiguous polarity. For some processing operations, such as shear-wave splitting analysis, it is vital that the direction and polarity of both horizontal elements is well understood.

The present state of the art for 3-C surveys is improving, yet a large percentage of 3-C surveys are shipped to processors with inadequate information on geophone orientation, element orientation (within the geophone), element-to-channel mapping, and element polarity. In many cases, the processor is forced to fill-in missing information with educated guesses. This has undoubtedly resulted in incorrectly processed data, and ultimately, a loss of money invested in acquiring multicomponent data. The development of standards for tap testing and recording could largely alleviate these concerns.