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Geophysics investigates the earth with the help of physical methods (e.g. measurements of electromagnetic fields) and helps to understand the interior processes of the inner earth (e.g. magnetism, earthquakes), surface-near processes (e.g. the impact of seismic waves to buildings), surface-near investigation of structures for engineering purposes (e.g. waste site investigation) and processes on the planets of our solar system.
By calibrating geological and geophysical results, geological structures and non-geological anomalies can be verified or dertermined with a much higher effiency as with one discipline alone.
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Geophysics supports (hydro-) geological and chemical investigations in a very good way. In geology, e.g. drill and soil samples can be analysed very detailed but only for a very small spot / area. Geophysics offers the opportunity to investigate and verify the space between these sample points in a fast and large vertical and horizontal scale. If geophysical measurements are calibrated with e.g. drill hole information, the space between drill holes can be much better interpreted in a geological way, in contrast to interpolations of geological models on the basis of drill hole information alone.
Such an integrated way was used at the EU-project NORISC (www.norisc.com). This project showed that with the help of an interdisciplinary waste site investigation and a tool for in-field data visualisation and modelling, a large reduction of time and costs is possible. With the investigation of the underground, geophysics locates possible "anomalies" which are given to (hydro-) geologists and chemists for a specific, target-oriented investigation in contrast to a standard investigation with an equally spaced sampling grid of the area. This interdisciplinary concept can be easily and successfully extended to questions of larger regions, e.g. for regional groundwater matters (see 'a comparison of geophysical and hydrogeological models'). Our working group wants to intensify the relations with the other earth disciplines and tries to calculate relevant parameters for e.g. hydro-geology directly.
Such an example is the so called "Induced Polarisation" method which measures the attenuation of currents within the earth. With the help of this method, the k-factor can be determined for a larger area.
Further examples are geophysical electrical resistivity / conductivity measurements which are used to investigate the structure of e.g. aquifers.
The following table gives an overview of the investigated fields and related methods in geophysics. | physical field | passive methods | active methods | | gravity field | gravimetry |
| | magnetic field (static) | magnetics |
| | electrical field (static) | Self potential | resistivity measurements | radiation,electro-
magnetical field
(time depending)
| natural radioactivity | VLF, RMT, EM-methods,
Induced Polaristion | seismic waves
| seismology | seismics |
Table 1: Division of methods in Applied Geophysics Figure 1 shows an example of the visualisation-software GSI3D from the NORISC-project. Aim of the investigation was to locate the source of the hydrocarbon pollution. The upper left shows the horizontal distribution of electrical resistivities as a result of a 3D-inversion in a relative depth of 3 m below the surface around the ground water table. Green und blue represent good conductors, indicating clay and silt, red and brown are bad conductors indicating sands. The coulored circles show the location of chemical samples, here for hydrocarbons. Green and yellow are non polluted areas, red and purple are about the allowed threshold level. It should be investigated if the hydrocarbons are related to rather clay / silt or the sand. As can clearly be seen the source of pollution is located within the clay / silt.
During rainy seasons, the hydrocarbons are washed out and reach an aquifer which is used for groundwater extraction.
In the lower part of the figure, geological and chemical information (vertical columns) are projected on a vertical resistivity. Blue indicates good conductors, red bad conductors.
The coloured columns show in the left and middle part geological information (fawn: sand; black and dark green: clay; blue: gravel, red: stones; white/grey: no information) and in the right part the hydrocarbon concentration (green: < 50 mg/kg, red: 100 - 300 mg/ kg, purple: > 300 mg/kg). There is a good correlation between geology and geophysics in the first few meters. A comparison between hydrocarbons and resistivities indicates that near the surface, where only sand and fillings are present, the resistivities are unusual low which can be a hint of bacteriological activity.
In greater depth, the relation between geology and geophysics grows weaker because of the bad signal-noise-ration of the geophysical measurement.
In the upper right of the figure, we see some vertical and a horizontal result of the resistivity measurements combined with borehole data (columns).
As a result, the remediation action was changed from a water remediation towards the excavation of the clay as the source of pollution. 
Fig. 1 shows a screenshot from the program GSI3D. Upper left: horizontal distribution of resistivities in about 3 m depth including related hydrocarbon locations (coulored circles). In the upper right we have a 3D view at some vertical and horizontal results from the resistivity measurements and the location of boreholes. In the lower part we see a result from a 2D inversion of a vertical resistivity profile. Geological and chemical borehole data is projected on the profile.
For my Ph.D. thesis, the program GSI3D is extended for a better in-field interpretation and calibration of geophysical data. This is realized by the ability of calibrating e.g. resistivity data from DC or RMT measurements with geological drill log data or resistivity Direct Push results. Thus, a more accurate geological underground model is created than by a single method alone and the position of contaminants and possible contamination plumes can be located with much higher accuracy.
List of add-ons for my Ph.D. for the GSI3D: modules for 2D-DC-resistivity- and 2D-RadioMagnetoTelluric- (RMT) and 1D-TransientElectroMagnetics (TEM) inversions modules for 2D-DC-resistivity- and 2D-RadioMagnetoTelluric- (RMT) grid creators routines for loading and displaying 1D data (DC, TransientElectroMagnetics, DirectPush), 2D data (DC resistivity & RMT ) and 3D data (normally DC; can also be used for different kind of data)
List of Publications - Perk, M., Tezkan, B., Hoerdt, A. (2003). Interdisziplinaere Altlastenuntersuchung (das EU-Projekt NORISC). 20. EMTF-Kolloqium der Deutschen Geophysikalischen Gesellschaft, Abtract-Band , S. 63 - 77
- Perk, M., Tezkan, B., Hoerdt, A. (2003). Interdisziplinäre Untersuchung einer Altlastflaeche in Köln (NORISC-Projekt). 63. Jahrestagung der Deutschen Geophysikalischen Gesellschaft. Abstract-Band, S. 400
- Perk, M., Tezkan, B., Hoerdt, A. (2004). Interdisziplinary Waste Site Investigation in Balassagyarmat (Hungary). EAGS / Near Surface Geopyhsics-Meeting. Extended Abstracts Book, B036
- Perk, M., Tezkan, B., Sobisch, H.-G. (2004). Der Feld-Einsatz der Visualisierungssoftware GSI3D (Geological Surveying and Investigation in 3D) im EU-Projekt NORISC am Beispiel der Testflaeche Balassagyarmat (Ungarn). Schriftenreihe der Deutschen Geologischen Gesellschaft (GeoLeipzig 2004, Abstract-Band), Heft Nr. 34, S. 386
- Perk, M., Tezkan, B., Hoerdt, A. (2004). Interdisziplinaere Untersuchung einer Altlastflaeche in Balassagyarmat / Ungarn (NORISC-Projekt). 64. Jahrestagung der Deutschen Geophysikalischen Gesellschaft. Abstract-Band, UI08
- Perk, M., Tezkan, B., Sobisch, H.-G. (2005). Kalibierung geophysikalischer Daten auf kontaminierten Flaechen mit Hilfe der Visualisierungssoftware GSI3D. 65. Jahrestagung der Deutschen Geophysikalischen Gesellschaft. Abstract-Band, S. 289
- Kremer, M., Perk, M., (2005). Minimierung des Restrisikos durch Altlast-untersuchungen. BEW (Bildungszentrum für Entsorgung und Wasser-wirtschaft), Forum Bodenschutz, September 2005
- Perk, M., Tezkan, B., Sobisch, H.-G. (2006): Infield-Kalibrierung geophysikalischer Daten auf kontaminierten Flächen mit Hilfe der Visualsierungssoftware GSI3D.- 66. Jahrestagung der Deutschen Geophysikalischen Gesellschaft. Abstract-Band.
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