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Interprétation conjointe de cartographies magnétique et électromagnétique des propriétés magnétiques des sols anthropisés

Abstract : The magnetic properties are involved in two geophysical exploration methods: the magnetic method with which we measure the spatial variations of the geomagnetic field, and low frequency electromagnetic method that an artificial electromagnetic field is emitted and we measure the response of soil this field.
The thesis presented here proposes a method for simultaneous interpretation of data from these two types of method. This may make it possible to characterize the different types of magnetization in the near subsurface of the soil and to better assess the depth and geometry of magnetic sources. An extensive magnetic survey conducted in the Hellenistic site of Apamea on the Euphrates shows the interest of such exploration in the context of a search of urgency and importance to refine the interpretation of magnetic data.
The first chapter presents a synthesis on the study of magnetic properties of soil samples. These properties allow to characterize the behaviour of surface horizons and to study pedological and anthropological soil processes. The magnetic and electromagnetic surveys can map the magnetic properties, maps that can be supplemented by studies on samples.
There are many electromagnetic devices for measuring apparent magnetic susceptibility but their performance, especially in terms of depths of investigation, are highly variable. A theoretical and experimental study conducted on a test site shows that the spacing and orientation of the coils selected for CS150 make the device with the best depth of investigation and the order of 1 m, and for which the conductivity of the ground has very little influence on the phase response.
The joint interpretation of magnetic and electromagnetic data is based on linear filtering of electromagnetic data which allows to restore the magnetic anomaly due to induced magnetization. The theoretical study shows that the main difference between the magnetic data and electromagnetic filtered data comes from the difference in depth of investigation between the devices.
Finally, experimental trials on archaeological sites have resulted in one case, to separate the remanent magnetization of the induced magnetization and calculate the depth of the magnetic source and the other case, to separate the viscous magnetization from the induced magnetization and here again to calculate the depth of the magnetic source.
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Contributor : Christophe Benech <>
Submitted on : Monday, August 31, 2009 - 1:16:30 PM
Last modification on : Wednesday, December 9, 2020 - 3:13:10 PM
Long-term archiving on: : Tuesday, June 15, 2010 - 7:42:02 PM


  • HAL Id : tel-00411992, version 1


Christophe Benech. Interprétation conjointe de cartographies magnétique et électromagnétique des propriétés magnétiques des sols anthropisés. Géophysique [physics.geo-ph]. Université Pierre et Marie Curie - Paris VI, 2000. Français. ⟨tel-00411992⟩



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