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→How MT differs from electric logs
==How MT differs from electric logs==
==How MT differs from electric logs==
[[Applying-magnetotellurics fig16-1.png|thumb|{{figure number|1}} Simplified relationship between a lithologic log, an electric log, an MT sounding, and an inversion run using the MT sounding data.]]
MT differs from an inductive electric log in three major ways:
MT differs from an inductive electric log in three major ways:
| Respond only to changes in average bulk resistivity || Respond to individual rock layers along the wall of the borehole
| Respond only to changes in average bulk resistivity || Respond to individual rock layers along the wall of the borehole
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[[:Applying-magnetotellurics fig16-1.png|Figure 1]] shows the simplified relationship between a lithologic log, an electric log, an MT sounding, and an inversion run using the MT sounding data. We can also take electric log data and run a forward MT model to produce an MT sounding curve.
==Subsurface layers resolved==
Subsurface layers are resolved by inverse modeling of MT data acquired across a spec- trum of frequencies, as illustrated in [[:Applying-magnetotellurics fig16-1.png|Figure 1]].
==MT resolution==
The rule-of-thumb for MT resolution for depth of burial vs. layer thickness is 10:1. For example, to “see” a layer at a depth of 1,500 m (5,000 ft), the thickness of the layer needs to be approximately 150 m (500 ft) or more. Low-resistivity layers are more easily delineated than high-resistivity layers. It is difficult for MT to resolve more than three or four subsurface layers.
==See also==
==See also==