THE LOG (RMS LG)-M(B) SCALING LAW SLOPE

The Lg phase has been demonstrated to have unusual stability and preci sion of relative scaling with the global m(b) or yield of nuclear expl osions on a path by path basis. However, Lg scaling slopes with magnit ude for different propagation paths are often quite different, an unex plained effect which complicates nuclear monitoring procedures. In thi s study, both data analysis and numerical simulations are used to expl ore the factors influencing Lg scaling. Digital seismic data from broa dband stations in Eurasia for explosions at the former Soviet Union nu clear test site in Balapan are analyzed. The data suggest that yield s caling of the source spectrum, combined with frequency selection prope rties of propagation on each path are responsible for the observed var iations in scaling slope. Loss of high-frequency energy by attenuation causes high scaling slopes along some paths. Variations in site effec ts and instrument responses may also contribute to the scatter of Lg s caling slopes. Numerical simulations, used to calculate synthetic scal ing laws, support these inferences.