Recent research has shown the stability of root-mean-square Lg measurements for the accurate estimation of yields of Soviet underground nuclear explosions. Hansen, Ringdal, and Richards (1990) presented log-rms Lg data for 16 well-recorded Soviet underground nuclear explosions from eight seismic stations in Norway, the USSR, and China and a worldwide mb measurement for the same events. These data were analyzed using a relative magnitude model in which the parameters represent relative or normalized versions of the station intercepts, slopes and log-yields from the usual seismic magnitude / yield relationship. These normalized parameters are estimable without yield data and are simple transformations of the actual station intercepts, station slopes, and log-yields.

Relative magnitude modeling permits comparisons of the seismic magnitude / yield relationships of the individual stations and the worldwide mb measurements without yield data. The slope at the China Digital Seismograph Network station Hailar was found to be significantly different from that of the other stations in the study. The residual analysis estimated the precision of the log-rms Lg measurements of well-recorded explosions to be 0.0279 in magnitude units, which is in agreement with the findings of Hansen, Ringdal, and Richards (1990).

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