Applied Geophysics

Seismics

Elastic wave are emitted by a artifical source (eg. sledge hammer, drop down). They propagate throught the subsurface, where they may be reflected, refracted or diffracted. Those waves, which reach again the surface, are recorded with sensors (geophones, hydrophones).

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Magnetics

Magnetic measurements measure the Earth’s magnetic field. Objects in the subsurface with different magnetic susceptibility than the surrounding material and/or with remanent magnetization cause small-scale anomalies in the measured field.

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Ground penetrating radar (GPR)

Ground Penetrating Radar (GPR) uses electromagnetic waves that are emitted by an antenna as short pulses into the subsurface. If the dielectric permittivity of the material changes, parts of the electromagnetic wave are reflected back and received by another antenna. An image of the subsurface is produced.

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Electromagnetic Induction (EMI)

Electric current can be induced in the subsurface by artifical or natural electromagentic sources. By analysing the observed electric and magnetic field the conductivity of the subsurface an be derived.

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Resistivity method

An apparent electrical resistivity is derived by measuring an electrical current flow between two electrodes and the difference of the electric potential between two different electrodes. A model of the spatial distribution of the electrical resistivity can be derived by analysing the measurements.

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