Course Introduction - II
What can (or cannot) a geophysical method detect?
If the subsurface is completely homogeneous then the value of the physical parameter you are measuring will remain constant.
However, to detect variations in the subsurface (change in state of the geologic material, or a contrast to a different geologic material such as layering, or a fault) then the value of the physical parameter must change.
Warning
Different geologic materials may have the same (or strongly overlapping) value of a given physical parameter. If so, then that interface between the material (e.g. a layer boundary) is invisible to that geophysical method.
The above concepts are nicely illustrated in the figure below taken from the I2AG (Introduction to Applied Geophysics) textbook. In this case using only one geophysical method would not allow you to detect both interfaces.
Three layers of different geologic materials and two interfaces as "seen/detected" or "not seen/not detected" by two different geophysical methods.
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