HR: 08:15h
AN: NS21A-02    [Abstracts]
TI: 3D constrained inversion of geophysical and geological information applying Spatial Mutually Constrained Inversion.
AU: * Nielsen, O F
EM: ofn@cowi.dk
AF: COWI A/S Denmark, Parallelvej 2, Kongens Lyngby, 2800, Denmark
AU: Ploug, C
EM: cpl@cowi.dk
AF: COWI A/S Denmark, Parallelvej 2, Kongens Lyngby, 2800, Denmark
AU: Mendoza, J A
EM: jame@cowi.dk
AF: COWI A/S Denmark, Parallelvej 2, Kongens Lyngby, 2800, Denmark
AU: Martínez, K
EM: kemr@cowi.dk
AF: COWI A/S Denmark, Parallelvej 2, Kongens Lyngby, 2800, Denmark
AB: The need for increaseding accuracy and reduced ambiguities in the inversion results has resulted in focus on the development of more advanced inversion methods of geophysical data. Over the past few years more advanced inversion techniques have been developed to improve the results. Real 3D-inversion is time consuming and therefore often not the best solution in a cost-efficient perspective. This has motivated the development of 3D constrained inversions, where 1D-models are constrained in 3D, also known as a Spatial Constrained Inversion (SCI). Moreover, inversion of several different data types in one inversion has been developed, known as Mutually Constrained Inversion (MCI). In this paper a presentation of a Spatial Mutually Constrained Inversion method (SMCI) is given. This method allows 1D-inversion applied to different geophysical datasets and geological information constrained in 3D. Application of two or more types of geophysical methods in the inversion has proved to reduce the equivalence problem and to increase the resolution in the inversion results. The use of geological information from borehole data or digital geological models can be integrated in the inversion. In the SMCI, a 1D inversion code is used to model soundings that are constrained in three dimensions according to their relative position in space. This solution enhances the accuracy of the inversion and produces distinct layers thicknesses and resistivities. It is very efficient in the mapping of a layered geology but still also capable of mapping layer discontinuities that are, in many cases, related to fracturing and faulting or due to valley fills. Geological information may be included in the inversion directly or used only to form a starting model for the individual soundings in the inversion. In order to show the effectiveness of the method, examples are presented from both synthetic data and real data. The examples include DC-soundings as well as land-based and airborne TEM-soundings. The SMCI here combines the capability of the DC- resistivity method to map resistive areas with the capability of the EM method to map conductive zones in order to produce models that are more in agreement with the expected geological formations. Furthermore, the results from the SMCI inversion are compared with traditional inversion methods. The comparison is made from resistivity maps where the resolution of the method can be evaluated with known lithology, water levels, etc. The results from SMCI inversion demonstrate significant improvement over those derived from standard 2D constrained inversion. The SMCI is applicable in general geological mapping, groundwater surveys, mineral exploration or other surveys where geophysical information of different types can be combined or where geological information is available.
DE: 0684 Transient and time domain
DE: 0699 General or miscellaneous
SC: Near-Surface Geophysics [NS]
MN: 2009 Joint Assembly