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

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