Entries in geophysics (13)


Techniques to Quantify Stream-Groundwater Exchange and Shallow Transport A Hands-on Workshop

Looking forward to participating in the upcoming workshop for hands-on experience with novel techniques that can be used to investigate stream-groundwater interactions. Participants will learn to apply four novel techniques and learn related experimental design, data acquisition, data processing, and analysis issues for stream-groundwater interaction studies. http://www.cuahsi.org/stream-gw-wkshp.html


Gamma Ray Logs

Gamma ray logging is a borehole tool that can provide useful information for environmental and engineering investigations and water resource exploration. In practice, the tool is sensitive to clay content, and functions as a sand/clay log for unconsolidated sediments, or a shale log in rock sequences. The method measures natural gamma irradiation from radioactive isotopes in the sediment/rock minerals. Potassium is the most common radioisotope in surficial geologic materials in the Midwest.

It is particulary helpful for wells with poor or absent boring logs, and can be useful in lithologic correlations. The method ties well with observed lithologic profiles and can be used to help constrain earth resistivity surveys. Ned Bleuer has applied gamma logging to the analysis of glacigenic facies (Indiana Geological Survey Special Report 65).

Gamma ray logs can be obtained from in situ wells and cased boreholes. Because it detects natural gamma radiation, there is no radioactive source within the tooling, and no NRC permitting is required.


GPR imaging of ground water seepage within an earthen dam



This is one slice of a 3-D radar survey performed at an earthen dam in northeastern Indiana (click the image to enlarge). The bright areas near the center of the image indicate ground water saturation. A geotextile layer is imaged as an inclined planar surface, and breaching of ground water from the geotextile into the fill lifts is observed. This indicates failure of the textile to route seepage to the toe drain.

Page 1 2 3