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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.[an error occurred while processing this directive] USGS Water Science Centers interested in learning more about the specific equipment systems the Branch supports should see the OGW BG Geophysical Equipment Program online information.

• Frequency-domain electromagnetic measurements
• EM-34
• EM31
• EM38
• GEM-2
• 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
• Compact digital logging systems.
• Caliper
• Gamma
• Single-point resistance
• Self potential
• Normal resistivity
• Fluid resistivity
• Temperature
• Magnetic susceptibility
• 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

• Borehole liners to prevent cross-contamination[an error occurred while processing this directive] (Internal USGS: Learn more!)
• Borehole wire-line packers and downhole transducer (for differential head measurements)
• Cross-well flow testing and monitoring
• Flowmeter logging in ambient or stressed, single- and cross-hole surveys
• Borehole heat-pulse flowmeter
• Borehole electromagnetic (EM) flowmeter
• Spinner flowmeter
• Multifunction borehole testing apparatus for discrete-zone hydraulic tests
• Semi-permanent packers to prevent cross-contamination and provide hydraulic-head and water-quality monitoring

• Continuous resistivity profiling (CRP)
• Continuous seismic profiling (CSP) [an error occurred while processing this directive] (Internal USGS: Learn more!)
• 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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