High-resolution surface topographic change analyses to characterize a series of underground explosions

The understanding of subsurface events that cannot be directly observed is dependent on the ability to relate surface-based observations to subsurface processes. This is particularly important for nuclear explosion monitoring, as any future clandestine tests will likely be underground. We collected ground-based lidar and optical imagery using remote, very-low-altitude unmanned aerial system platforms, before and after several underground high explosive experiments. For the lidar collections, we used a terrestrial lidar scanner to obtain high-resolution point clouds and create digital elevation models (DEMs). For the imagery collections, we used structure-from-motion photogrammetry techniques and a dense grid of surveyed ground control points to create high-resolution DEMs. Comparisons between the pre- and post-experiment DEMs indicate changes in surface topography that vary between explosive experiments with varying yield and depth parameters. Our work shows that the relationship between explosive yield and the extent of observable surface change differs from the standard scaled-depth-of-burial model. This suggests that the surface morphological change from underground high explosive experiments can help constrain the experiments' yield and depth, and may impact how such activities are monitored and verified.