A comparative analysis of geophysical fields for multi-sensor applications Kamil Erkan ⁎, Christopher Jekeli Division of Geodetic Science, School of Earth Sciences, The Ohio State University, 125 S. Oval Mall, Columbus, OH, 43210 USA abstract article info Article history: Received 29 May 2009 Accepted 30 March 2011 Available online 12 April 2011 Keywords: Multi-sensor Integrated modeling Detection Gravity gradiometry Geologic investigations based on the measurement of a single geophysical field usually result in an ambiguous interpretation, whereas combining measurements of multiple geophysical fields (multi-sensor approach) leads to more reliable earth system models. A fundamental problem in the multi-sensor approach is that the response of each geophysical field to the earth's subsurface is different, which may result in discordant observations. We suggest that a common approach to geophysical fields and their applications (geophysical methods) would contribute to establishing efficient multi-sensor systems. In this study, we compare the conventional geophysical methods from both theoretical and practical aspects using their common terminologies, which reveal their basic analogies and differences. In particular, we compare shallow applications of geophysical methods as the multi- sensor approach is vitally useful for such problems. We finally discuss a practical tool for side-by-side comparison of detection reliabilities of different geophysical methods. This technique can set conditional or unconditional requirements on methods depending on a particular subsurface problem. Examples of the detection reliability from gravity gradiometry, magnetometry, and ground penetrating radar (GPR) are presented. Published by Elsevier B.V. Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142 2. A unified approach to geophysical fields . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143 3. Analogies in geophysical methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143 3.1. Static/stationary fields . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144 3.2. Quasi-stationary fields . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144 3.3. Transient fields . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145 4. Geophysical methods for shallow applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145 5. Detection reliability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145 5.1. Gravity gradiometry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 146 5.2. Magnetometry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 146 5.3. GPR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 146 6. Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 147 7. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149 1. Introduction In solid earth sciences active and passive geophysical fields are used to obtain knowledge of the subsurface. Information obtained this way is never complete due to the inability of direct sampling of the earth's subsurface (Parker, 1977). As a consequence of this, a single geophysical method usually does not provide all the necessary information needed for a successful geophysical survey; and a variety of geophysical fields have to be incorporated to increase the reliability of the final interpretation. Using information theory, Khesin et al. (1996) argued that compared to increasing accuracy from a single type of geophysical sensor, use of multiple geophysical sensors provides far greater information of the subsurface target. Furthermore, Raiche et al. (1985) showed that combined data from different geophysical methods can have a synergetic effect on the final model that is beyond a compromised model among a family of ordinary models. Journal of Applied Geophysics 74 (2011) 142–150 ⁎ Corresponding author. Tel.: +1 614 292 2721; fax: +1 614 292 7688. E-mail address: erkan.1@geology.ohio-state.edu (K. Erkan). 0926-9851/$ – see front matter. Published by Elsevier B.V. doi:10.1016/j.jappgeo.2011.03.006 Contents lists available at ScienceDirect Journal of Applied Geophysics journal homepage: www.elsevier.com/locate/jappgeo