A level-set approach for joint inversion of surface and borehole magnetic data

We present a level-set approach to investigate the joint inversion of surface and borehole magnetic data for target delineation in mineral exploration. The method is an extension of the recently developed level-set inversion algorithm for surface magnetic data only. The level-set inversion provides novel means to alleviate the difficulties caused by the ambiguity in the source distance from the observation, and opens new avenues for examining a class of magnetic inverse problems that are of more practical importance. We examine the ability of such inversion in resolving the configuration and spatial separation of complex magnetic sources that are difficult to achieve in general unless site specific parametrization is adopted. We also examine the use of sparse borehole intersection information in estimating the crucially important susceptibility values within the context of level-set inversion. We demonstrate that the modified level-set inversion provides an effective means to image and delineate magnetic causative bodies with complex structure by jointly inverting surface magnetic data, borehole magnetic data, and sparse drill hole intersection data.