Office of Ground Water
Branch of Geophysics
Geophysical Methods
Applied geophysics research at OGW, BG focuses on
the development and modification of geophysical characterization and monitoring
methods and on the testing of newly developed and emerging geophysical technologies.
OGW, BG uses a variety of geophysical methods and techniques in its ongoing
research and training courses.
Below is a listing of the surface,
borehole, and water-borne geophysical
methods supported by OGW, BG, including emerging techniques under development.
The Branch also supports selected methods for hydraulic
testing in boreholes that are commonly used in conjunction with borehole
geophysical methods.
For additional
information and online support materials for many of these methods, see the
OGW, BG online technology training and transfer information.
- Frequency-domain electromagnetic measurements
- Ground-penetrating radar (GPR)
- Continuous profiling at 80 to 500 megahertz (MHz)
- Step profiling at 25 to 400 MHz
- Applications requiring shielded antennas
- Induced polarization (IP)
- Magnetometer
- Self potential (SP)
- Seismic surveys
- Shallow refraction
- Shallow 2-D and 3-D reflection
- Shallow direct-current (DC) electrical resistivity sounding
- 2-D Resistivity with roll-along capability provides for longer co-linear arrays
- Square-array azimuthal measurements for up to 150-meter square arrays
- Surface magnetic resonance sounding (MRS) -- also known as nuclear magnetic resonance (NMR)
- Time-domain (transient) electromagnetic surveys
- Very low frequency (VLF) electromagnetic measurements
- Integrated global-positioning system (GPS) data in all surveying
- Standard borehole logging methods
- Borehole electromagnetic (EM) induction logging
- Single induction
- Dual induction
- Borehole imaging
- Acoustic Televiewer
- Optical Televiewer
- Borehole video camera (for assessing borehole conditions)
- Borehole radar
- Single-hole reflection logging
- Single-hole directional logging
- Cross-hole tomography
- Surface-to-borehole surveys
- Deviation
- Electrical resistance tomography (ERT)
- Single-hole arrays
- Cross-hole arrays
- Full waveform sonic
- Neutron porosity
- Single detector
- Dual detector
- Spectral gamma
(See a summary of selected borehole logging methods and their relative
cost, difficulty, and speed.)
In addition to processing and analysis of the above methods,
OGW, BG also supports:
- Integrated interpretation of borehole logs
- Geostatistical analysis of tomographic data and for planning tomographic investigations
- Continuous resistivity profiling (CRP)
- Continuous seismic profiling (CSP)
- High frequency
- Low frequency
- Swept frequency chirp
- Marine radar profiling
- Single-channel bathymeter
- Integrated global-positioning system (GPS) data in all surveying
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