Class Code: 8606
Per NCCI's Scopes Code Description:
Code 8606 is applicable to the various methods of geophysical exploration. Each method exploits fundamental physical aspects of earth material to infer the most likely properties of large volumes of rock. The most common methods of geophysical exploration include gravitational, electric, magnetic, and seismic. These surveys are often used by the oil industry to locate oil and natural gas.
The gravitational method uses delicate pendulums and torsion balances that are capable of detecting differences in the gravity pull of the earth at various places. This enables a geologist to tell where oil is likely to be found.
There are two electrical methods—resistivity and inductive. In the resistivity method, measurements are taken on an ohmmeter, which indicates the resistivity of the subsurface. The inductive method determines the conductivity of subsurface formations. Both methods enable the geologist to determine the character of the subsurface being studied.
The magnetic method uses a highly developed form of magnetic dipping needle with a telescope magnifier. The magnetic attraction exerted by magnetic rocks, formations, etc., causes the needle to deflect from its horizontal plane, thereby enabling a geologist to develop contour maps with lines of equal magnetic attraction.
Geophysical exploration using the seismic method is the study of “earthshaking” events. These events may be natural, such as earthquakes or meteorite hits, or manufactured, such as bomb detonations. Seismic waves are the vibrations that travel through earth’s subsurface as a result of these earthshaking events. Geologists set up instruments known as seismographs to record these vibrations and interpret the recordings to reach conclusions regarding the time, location, and magnitude of these events. Additionally, geologists may initiate their own events using equipment such as dynamite, guns, or sledgehammers to create vibrations that are to be measured.
Geophysical exploration crews are classified to Code 8606 when these activities are conducted as a separate and distinct business.