Geoscience Reference
In-Depth Information
8 Magnetometry, Self-
Potential, and Seismic
Additional Geophysical Methods
Having Potentially Significant
Future Use in Agriculture
Barry J. Allred, Michael Rogers, M. Reza Ehsani,
and Jeffrey J. Daniels
ContentS
8.1 Magnetometry Methods ...................................................................................................... 147
8.1.1 Magnetometry Method Introduction ....................................................................... 147
8.1.2 Types of Magnetometers.......................................................................................... 148
8.1.3 Magnetometry Field Principles................................................................................ 149
8.1.4 Magnetometry Data Processing and Analysis ......................................................... 149
8.1.5 Magnetometry Agricultural Application Example .................................................. 151
8.2 Self-Potential Methods........................................................................................................ 152
8.2.1 Self-Potential Method Introduction ......................................................................... 152
8.2.2 Sources of Consistent and Unidirectional Natural Electric Potential Gradients ..... 153
8.2.3 Self-Potential Equipment, Field Procedures, and Data Analysis Products ............. 153
8.2.4 Possible Agricultural Applications for Self-Potential Methods............................... 155
8.3 Seismic Methods ................................................................................................................. 155
8.3.1 Seismic Method Introduction................................................................................... 155
8.3.2 Seismic Wave Types................................................................................................. 156
8.3.3 Aspects of Seismic Wave Propagation..................................................................... 157
8.3.4 Seismic Method Data Collection, Data Analysis, and Potential Agricultural
Applications ............................................................................................................. 160
References ...................................................................................................................................... 161
8.1
MAGnetoMetRy MethodS
8.1.1 M a g n e t o M e t R y M e t h o d i n t R o d u c t i o n
Magnetometry is a passive remote sensing method that records the magnitude of Earth's local mag-
netic field at a sensor location. The Earth's overall magnetic field is a dipole field with the North
Magnetic Pole and the South Magnetic Pole acting much like the ends of a bar magnet. There are
secondary regional and local variations to the primary dipole field caused by soils and objects with
different magnetic properties located above, on, or beneath the ground surface. Historically, the
oersted and gamma have been the common units for measuring variations in Earth's magnetic field,
147
 
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