The key to success in recording multiple data sets simultaneously from multiple sets of sources is being able to separate the multiple data sets satisfactorily. If at a given receiver position the energy level is greatly different from one source than from another source, then we may have difficulty in extracting the weaker trace from the stronger trace. We operated two sets of sources at two adjacent source positions, so that the energy levels from the two sets of sources at any receiver position were not greatly different and satisfactory separation of the traces was relatively easy. Reflections from adjacent source positions as recorded at any receiver position were also similar in that the rays were reflected from adjacent reflection points at depth. Actually, of course, our measurements responded not to rays but to waves which were reflected from rather large areas surrounding the reflection points. Reflections from adjacent reflection points were actually from areas which overlapped substantially; therefore, signals reflected from adjacent reflection points would not have been totally independent even with conventional recording from one set of sources. Slight, additional contamination of one trace by an adjacent trace because of less than perfect separation of simultaneously recorded data was of little consequence with our technique. We saved money by speeding up recording, and data quality was excellent. In our application of the technique the reflection targets were rather shallow, but the technique is not limited to shallow exploration.To best meet our exploration objectives, we used simultaneous recording to save field time and money. We used nonlinear sweeps in the field along with effective spectral flattening processing techniques to bring out higher frequencies and improve resolution. We used the stack-array technique (Anstey, 1986) to suppress noise in the stacked data better.Some have objected that our technique cannot possibly work, and have shut their minds against discussion and favorable evidence. However, this technique is based upon nothing more controversial than a valid application of the theorem of superposition. Furthermore, the technique was validated by field results including the recording of 73 mi (117 km) of excellent data in 1984 and 1985 at relatively modest costs.

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