Chapter 6: Magnetic Methods in Near-Surface Geophysics
The Role of Magnetic Methods in Near-Surface Investigations
Magnetic methods have a prominent place in near-surface geophysics for a number of reasons. First, the sources of interest often have strong magnetic signatures; sometimes the only measurable geophysical property of the target is its magnetic field. Some examples will be given later in the chapter. Second, magnetic measurements are comparatively simple, rapid, and completely noninvasive. Although the resolution required for near-surface applications generally makes airborne data acquisition impractical, even this is possible in some cases. Finally, in near-surface investigations magnetic data are often easy to interpret; in some cases, visual inspection of essentially raw data is sufficient. For all these reasons, magnetic methods are widely used in almost all areas of near-surface geophysics. In some subfields, such as buried ordnance detection, magnetic methods are particularly important.
Figures & Tables
Near-surface geophysics uses the investigational methods of geophysics to study the nature of the very outermost part of the earth’s crust. Man interacts with this part of the earth’s crust: he walks on it; he drills and excavates into it; he constructs structures on and in it; he utilizes its water and mineral resources; and his wastes are stored on and in it and seep into it. The very outermost part of the Earth’s crust is extremely dynamic-in both technical (physical properties) and nontechnical (political, social, legal) terms-which leads to both technical and nontechnical challenges that are much different than the challenges faced by “traditional” applications of geophysics for regional geologic mapping and for oil and gas exploration (see Chapter 2).