Teleseismic body-wave magnitudes due to nuclear tests at Yucca Flat, Nevada, display a fluctuation of approximately ±0.2 mb units. The magnitude anomaly correlates well with geologic structure at this test site, and it is hypothesized that a seismic response model of the local structure could account for most of the variance in the magnitude observations.
A detailed model of the geophysical structure along a profile near the center of Yucca Flat has been constructed from independent geologic and geophysical data. The seismic response of this model has been calculated for a global network of six observing stations. The theoretical mb anomaly compares favorably with the observed anomaly. Corrections to the observed magnitudes based on the model would result in an order of magnitude decrease in the variance of the observations.