abstract
A model is presented for the simultaneous detemination of the relative variation in transmission properties to different stations and of the relative differences between the seismic sources for closely spaced underground nuclear explosions recorded by a fixed seismological station network. The model is applied to short-period data reported from 24 globally distributed stations from 12 underground nuclear explosions with known yields at Nevada Test Site. The obtained transmission functions vary within a factor of 10 between the different stations and show a weak decrease with epicenter distance and little correlation with the Gutenberg amplitude-distance curve. The relative source functions for 10 explosions in tuff and rhyolite, with yields in the range 16 to 1,200 kt, are with good correlation proportional to explosion yield to 0.9. Two theoretical source-function models, one by Haskell (1967) and one by Mueller and Murphy (1971a), are compared with each other and they agree well for frequencies around 1 Hz and for yields in the range 3 to 300 kt. The Haskell model for tuff is modified to be more compatible with the models for salt, granite and alluvium. The Haskell model predicts stronger variation of the source functions with frequency and yield than the Mueller-Murphy model. The observed relative source functions are compared with the theoretical source functions obtained from the two source models. The agreement is fairly good but the relative decrease of the source functions at yields above 300 kt predicted by the theoretical models is not observed.
