Joint 3D of muon tomography and gravity data to recover density

Abstract

Cosmic rays producing muons shower the Earth daily. These natural, high-energy particles decay as they pass through matter and are directly affected by density. Recently, sensors have been placed in existing tunnels and mine shafts that observe muon flux in a brown-field mining scenario. We have developed an algorithm to invert these data individually, or jointly with gravity data, to recover a 3D distribution of density. Muon and gravity data are both linear functionals of density but the associated sensitivity functions are substantially different. These differences in physics between muon ray paths and gravity data provide a unique insight into the subsurface. This is illustrated through synthetic examples. Inversion of a set of field data, obtained at a mine site in south-west British Columbia, Canada, illustrates the potential benefits and challenges for the technique to be used in field surveys.