In June 2007 CREWES sponsored the acquisition of a polychromatic survey. A vibrator source was used to collect surface seismic data in several narrow frequency ranges, with sources and receivers arranged in a typical 3-D acquisition layout. Data from a 2-D line of receivers show expected features for correlated shot records. Individual uncorrelated traces differ greatly in appearance between narrow-band and broad-band cases.
The broad-band data, correlated and uncorrelated, can be decomposed by bandpass filtering into approximations of narrow-band data. The pseudo-narrow-band correlated shot records are similar in appearance to the true narrow-band shot records, particularly at lower frequencies. In the reverse operation, narrow-band shot records can also be combined to mimic a broad-band shot record. However the narrow frequency bands produce Klauder wavelets with pronounced side lobes, and these persist into the combined result. Using more smoothly defined bands would help to alleviate this shortcoming. Decomposing broad-band uncorrelated traces appears to produce little similarity to narrow-band traces. Expanding the time window of the sweep related to a given frequency range however reveals a degree of similarity. Multiple sweeps were collected for each source-receiver pair, and displays of repeated sweeps show a high degree of reproducibility.
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