UXO Characterization by 3D Seismic Constrained Magnetometry Inversion

Marine Unexploded Ordnance (UXO) identification and clearance is a massive growth industry, driven by the expansion into deeper water resources and offshore renewables. The standard survey too of choice is a magnetic gradiometry system, which benefits from being cheap, easy to use, and able to rapidly cover spatially extensive areas. In theory, using the 3D Analytical Signal, such systems are also capable of characterizing the magnetic susceptibility of the UXO targets. Given the huge areas to cover and often large number of identified targets, this kind of material properties information is invaluable for distinguishing between UXO that need removing and those that can remain in situ. However, inversion of the Analytical Signal is a multi-paramter, non-unique process, difficult to perform reliably based on magnetometry data alone. Here we demonstrate the combined use of decimetre-resolution 3D seismic and gradiometer data for UXO characterization. The 3D seismic data are used to constrain the location, size, and burial depth of UXO targets prior to inversion of the Analytical Signal. Together, these techniques are used in combination to characterize 89 UXO targets that are verified using post-survey dredging.