Five different geophysical methods were used near Sierra Vista, Arizona in order
to determine the presence or absence of impermeable silt-clay layers in reference to a
proposed water-retention system. Geophysical investigations were conducted at
Woodcutters 3 and Basin Floor 1 (both approximately one kilometer long north-south and
east-west transects), and School Basin (10 meter by 50 meter area where only TEM data
were collected). Magnetic, VLF, seismic, EM 31 and 34, and TEM survey data were
collected on February 28th and 29th and March 20th and 21st of 2004. Magnetic and VLF
surveys conducted at the Woodcutters 3 and Basin Floor 1 sites had relatively flat profiles
that indicated only a few single-station anomalies with little difference between the two
sites. Seismic survey data produced velocities in two-layer earth models that were similar
between the two sites in the upper 5 meters, again indicating little difference between the
sites. The EM 31 and 34 surveys, with depths of investigation in the 3-6 meter range,
measured higher ground conductivity values in the upper 10 meters at the Woodcutters 3
site. This agreed with shallow borehole data from the Woodcutters 3 and Basin Floor 1
sites. The higher ground conductivity is indicative of higher water content, which may be
due to the increased percentage of clay. For the TEM surveys, conducted at all three sites
and with depths of investigations in the 0-50 meter range, it was found that a low
resistivity layer at 30-50 meter depth resides at the Basin Floor 1 site. This layer is deeper
than the available borehole data. At both sites the borehole data do not show definitive
clay layers, making it difficult to correlate the high conductivity values with clay content
percentages.
| Identifer | oai:union.ndltd.org:arizona.edu/oai:arizona.openrepository.com:10150/624621 |
| Date | 07 June 2004 |
| Creators | Asbury, Nicholas A., Barker, Margaret E., Blainey, Joan, Fabijanic, J. Matthew, Hazwezwe, Nchimunya M., Miller, Thomas E., Musosha, Chalwe P., O’Brien, Gillian E., Sternberg, Ben K. |
| Contributors | University of Arizona |
| Publisher | LASI Laboratory for Advanced Surface Imaging, The University of Arizona (Tucson, AZ) |
| Source Sets | University of Arizona |
| Language | en_US |
| Detected Language | English |
| Type | Book |
| Rights | Copyright © Arizona Board of Regents |
| Relation | LASI, http://www.lasi.arizona.edu/ |
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