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Joint And Cooperative Inversion Of Magnetic And Time Domain Electromagnetic Data For The Characterization Of UxoNormal access

Authors: Leonard R. Pasion, Stephen D. Billings and Douglas W. Oldenburg
Event name: 16th EEGS Symposium on the Application of Geophysics to Engineering and Environmental Problems
Session: Unexploded Ordnance
Publication date: 06 April 2003
Organisations: EEGS
Language: English
Info: Extended abstract, PDF ( 1.18Mb )

Summary:
Magnetics and electromagnetic surveys are the primary techniques used for UXO remediation projects.
Magnetometry is a valuable geophysical tool for UXO detection due to ease of data acquisition and its ability
to detect relatively deep targets. However, magnetics data can have large false alarm rates due to geological
noise, and there is an inherent non-uniqueness when trying to determine the orientation, size and shape of
a target. Electromagnetic surveys, on the other hand, are relatively immune to geologic noise and are more
diagnostic for target shape and size but have a reduced depth of investigation. In this paper we aim to improve
discrimination ability by developing an interpretation method that takes advantage of the strengths of
both techniques. We consider two different approaches to the problem: (1) Interpreting the data sets cooperatively,
and (2) Interpreting the data sets jointly. For cooperative inversion information from the inversion of
one data set is used as a constraint for inverting another data set. In joint inversion, target model parameters
common to the forward solution of both types of data are identified and the model parameters from all the
survey data are recovered simultaneously. We compare the confidence with which we can discriminate UXO
from non-UXO targets when applying these different approaches to results from individual inversions. In
this paper we focus on the details of the joint and cooperative inversion methodologies. Examples of the application
of the methodology to TEM and magnetics data sets collected at the former Fort Ord in California
are presented. This work is funded in part by the U.S. Army Engineer Research and Development Center
and the Army Research Office.

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