During the summer of 1980, faculty and students from the Colorado School of Mines Geophysics Department conducted an extensive series of seismic measurements in eastern Colorado, with the objective of characterizing and comparing land seismic sources under a variety of controlled conditions. This work was sponsored by 29 companies and one U.S. government agency, and results are reported in full in a series of Master of Science theses completed during the fall term, 1981, at Colorado School of Mines.

The test site for the measurement program was located near Brush, Colorado, on gently rolling range land. The site was selected on the basis of easy access, geology suitable for the program objectives (thick Pierre Shale section near the surface and good reflectors at depth), nearby petroleum production and well-log information, and a landowner willing to establish a permanent test site.

The seismic sources used in this study included: (1) vertical and horizontal vibrators, (2) land airgun, (3) weight drop, (4) conventional explosives in shot holes, (5) surface explosives, (6) suspended charges in air (Poulter method), (7) Marthor (registered trademark of IFP), and (8) Betsy (registered trademark of Mapco).

The measurement program consisted of three phases: (1) three-component downhole measurements from 400 to 1,000 ft (120 to 300 m) in 100-ft (30 m) intervals for each source type over a range of horizontal offsets from 50 to 1,000 ft (15 to 300 m); (2) three-component noise spread on the surface for each source covering an offset range of 120 to 8,730 ft (37 to 2,660 m); and (3) a conventional CDP line for each source covering 3 mi (4.8 km) of subsurface with a maximum of 24-fold coverage over the center 1 mi (1.6 km).

The primary test objectives consisted of: (1) quantitative comparison of source waveforms, amplitude and phase spectra, source repeatability, source directivity, and intensity levels from downhole measurements, (2) comparison of surface-wave noise-generation characteristics between different sources from noise spread data, and (3) quantitative comparison of reflection signal characteristics (e.g., bandwidth, S/N ratio, etc) from the CDP shooting.

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