Applied Geophysics – a scientific approach including a series of non-destructive survey methods, based on the precise registration of the physical manifestations of the sub-surface environment. Changing conditions in the sub-surface environment cause deformations of the related part of the registered physical field. The variability of the environment, structural failures, infiltration and increased concentration of natural and anthropogenic factors are the elements affecting the physical manifestation of the prevailing environment.

Applied
Geophysics
Geoelectrical
methods
Gravimetry Magnetic
methods
Radionuclide
methods
Seismic
methods

They are among the world's most widely used geophysical methods. Depending on the subject matter, the surveyed end-point is electrical resistance, dielectric constant or a change in the electric field potential. According to the used physical principle, they are broken down into resistant, electromagnetic and induction measuring. The data collection methodology and their processing procedure is selected according to the type of addressed issue and studied phenomenon.

The active development of such methods occurred at the beginning of the 20th century, but English scientist, Robert Were Fox is considered to be the pioneer. In 1830, he experimentally proved the existence of a natural electric field in the vicinity of sulphide ore deposits. His observations also revealed the relationship between the electric field intensity, quantity and concentration of copper in the ore. He used the acquired knowledge and experience in mapping ore veins in copper mines which locates sites with a higher concentration of copper and the advancement direction of abundant ore position.

During the 19th century, many scientists in various places imitated Fox's experiment while most of them can confirm his observations. Their successful tests demonstrate the possibilities of practical use with this method in ore prospection.

In 1880, the US Geological Survey () hired physicist, Carl Barus, whose task was to follow the research of R. W. Fox. During the experiments, Barus was aware that a natural electric field is generated directly by ore body, on the basis of which he concludes that by mapping the equipotential lines of the electric field it is possible to determine the position and approximate spatial course of the ore body. His assumptions were confirmed only in part because of the choice of inappropriate location for his experiment. In fact, his work is an important contribution to the development of these methods.

At the beginning of the 20th century, French physicist, geologist and miner Conrad Schlumberger, chose a different approach; using an artificial source he generates electric field in the environment and at the same time with the changing distance of current electrodes he measures the change in the field potential difference between the other two potential elektrodes. He successfully applies this approach for several exploration campaigns of ore and structural geological exploration. Schlumberger´s proposed method is suitable for the identification of changes in the electrical properties of the environment in a vertical direction (layered environment). In addition, in the same period Schlumberger significantly contributes to popularising of the methods using a natural electric field, when in 1914 he discovered a rich ore deposit in Serbia, in an area where the previous conventional exploration methods had not indicated the presence of the identified deposit. Schlumberger, together with his team established) other sector of the geophysical survey, i.e. drilling geophysics (Well Logging), in that time he used the modified principles of surface electrical methods that he effectively applied in exploratory wells worldwide. Drilling geophysics in the next period developed into a highly specialised scientific discipline encompassing all sectors of surface geophysics. In 1931 Conrad Schlumbergeris the founder of the company which has been the leader in geophysical exploration.

In 1912, American physicist Frank Wenner, an employee of the US Bureau of established standards (now )is devoted to the issue of precise surface measurements of electrical potentials. The conclusions drawn from laboratory experiments are verified in field conditions by small-scale experiments. He compiles theoretical apparatus on the base of the results obtained, describing the relationship between electrical resistance, depth and mutual distance of the electrodes. He published the conclusions of this work in in „A method of measuring earth resistivity“, where he also mentioned the perspective of the method on a much larger areal extent. His field measurements were carried out at several square metres which corresponded to the nature of the addressed issue. In the next period, the prerequisite for effective application on a larger scale was confirmed and Wenner¿s method was applied particularly for work aimed at identifying the physical contrasts in a horizontal direction.

Workflow fieldwork introduced by Conrad Schlumberger and Frank Wenner are still the most widely used and are named after their authors.

Electromagnetic methods, are among the most widely used in the world due to their mobility and data collection speed. Because of the high demands for technical implementation of apparatuses, their development was significantly delayed compared with other geoelectric methods. In 1918, Swedish mining engineers, Hans Lundberg a Harry Nathorstintroduced a unique method using electromagnetic field generated between two long parallel-laid grounded wires. On the area between the cables, covering approx. 100 [ha], they mapped ore deposit which is defined by anomalous behaviour of equipotential lines. In the following years, their method wassuccessfully applied in many locations in Sweden.

American electrical engineer and mining engineer, deals with the possibility of using electromagnetic induction in ore exploration and in 1917, he patented "". His experiments didn´t lead to satisfactory results but built a base for further development of the sector.

Swedish mining engineer, Karl Sundberg verifies the possibilities of several methods of electric and electromagnetic prospecting. In 1922, he put a modified method of H. R. Conklin into practice which is successfully applied in many countries and its efficiency has significantly supported the further development of electromagnetic methods.

Resources:

. Interpretation of resistivity data. Washington: United States Government Printing Office, .

.Study of underground electrical prospecting. Translated by: Kelly,Sherwin. Paris: [s.n.], .

. Úvod do užité geofyziky. Praha: SNTL - Nakladatelství technické literatury, . ISBN: 80-03-00427-6