Integration of Noble Gas and Seismic Measurements for Small Yield Event Discrimination and Yield Estimation

The experiment series will include a series of explosions above and below the water table to evaluate the influence of water saturation on gas transport. The explosions will have different yields and depths of burial in order to examine the effects of these important parameters on the gas transport as well as on seismic wave radiation. The below water table GDE will be the first of its kind. Even if SF6 is completely sequestered beneath the water table due to capillary effects, it would be an important result. We will perform extensive pre- and post-explosion subsurface site characterization, including cross-hole tomography, TEM/DC resistivity formation fracture aperture mapping, slug testing, and rock coring to characterize the subsurface properties (density, porosity, fracture density, and permeability) as a function of distance from the explosion source. In addition, we will collect and analyze seismic data from the explosions. Seismic data from the explosions with different emplacement conditions (combined with known gas signatures) could provide additional information for detection and yield estimation of small explosions, such as those apparently being conducted by N. Korea. We are particularly interested in determining whether there is correlation between the shear wave amplitudes, the formation of long fractures and the prompt venting of the tracer gas following the formation of the long fractures.