What is it like to be a geophysicist

What is geophysics? A tutorial.

The website www.geophysik.de was launched over 15 years ago as “The information portal on geophysics”. Now the site is presented in a new guise as a pure partner site of www.ernstson.de, whereby the original claim to provide information in the form of a tutorial about geophysics, its applications and measurement methods - especially in the service sector - has been maintained.

A short “hike” through geophysics.

What is geophysics? The importance in the geosciences, in geology, hydrogeology, geotechnical engineering, in reservoir, environmental and engineering issues and in archeology.

Geophysics means "physics of the earth" and deals with the material properties and physical processes in and above the earth. Geophysics means earthquakes, geomagnetism, gravity, geothermal heat, earth currents and so on ..

In very many cases, geophysics means that physical measurements are used to look into the subsurface, in some cases to great depths, and to make statements about the structural composition and material content. Geophysics is looking, for example, for deposits such as crude oil, natural gas, coal, ores, water, stones / earths, today increasingly the deposit for geothermal energy, and helps with their development. These deposits are searched for geophysically because they are tied to certain geological structures and their material properties stand out; they are foreign bodies in the earth's crust, and the geophysicist often speaks of disruptive bodies.

Foreign bodies, in the truest sense of the word also disruptive bodies in the earth are contaminated sites, landfills, old armaments, barrels, bombs, etc. with anomalous material properties. It is therefore consistent, for example, to treat contaminated sites with the exact methods, measurement and evaluation methods of geophysics.

Environmental geophysics in general means the use of geophysical measuring methods in the environmental field that correspond to the current state of science and technology.

Geophysics examines non-destructively. Instead of punctiform outcrops through boreholes, continuous observation and integration over larger volumes can take place. Geophysical measurements are inexpensive. Example: For the costs of a 100 m drilling, geoelectrical depth soundings can be carried out at roughly 100 (!) Locations with the same investigation depth.

But: Geophysical measurements - especially with the potential method - provide imprecise depth information. The vertical resolving power - again especially with the potential method - is low. (The high resolution of ground penetrating radar can rarely be used because of the often very low penetration depth.) - Results of geophysical measurements very often lead to ambiguities, which can, however, be limited by complex procedures (i.e. the combined use of different methods). At many localities in the environmental area, geophysical measurements can only be carried out to a very limited extent due to a variety of disruptive factors and often not at all. Certain problem cases - e.g. direct detection and spread of organic compounds, oil in the subsurface - currently cannot be resolved seriously.

Geophysics can only be viewed as an inexpensive replacement for drilling in the rarest of cases (geophysics and drilling). The characteristics of direct exposure through drilling and indirect exploration through geophysics are eminently different. Example: If the relief of the bottom of the landfill is to be determined in an existing landfill and any damage caused by drilling is to be excluded, there is only the alternative of high-resolution (and thus cost-intensive) seismics or waiver of the investigation!

In a project, if necessary, drilling / exploration / prospecting and geophysics must be coordinated with one another in terms of scope, time and costs. It can be useful to carry out geophysical measurements after exposed outcrops. As a rule, it will be wiser to start a geophysical campaign beforehand in order to set the holes according to the results of the geophysics. A clever combination enables the connection of geophysical profiles or measuring networks to the boreholes for subsequent calibration of the evaluation.

Cord Ernstson

Consulting geophysicist and geologist (Consultant) with an office for geophysical measurements in Höchberg near Würzburg

Graduated geophysicist

PhD, Dr. rer. nat., in geophysics

habilitation, Dr. rer. nat. habil., in geology

Professor at the University of Würzburg