m (sub b) :M (sub s) screening revisited for large events

Event screening of large-magnitude events (M (sub w) > or =5) based on m (sub b) :M (sub s) is revisited to account for the effect of the source corner frequency relative to the fixed frequencies of the long-period M (sub s) and short-period m (sub b) . For large events this source effect increases the slope of m (sub b) :M (sub s) relative to the 1:1 value expected for small events. The effect is demonstrated in the large earthquake m (sub b) :M (sub s) population and in the behavior of large theoretical explosions that are consistent with the more limited explosion population. The behavior is used to create a more conservative screening criterion that ensures large explosions are not inadvertently screened out by m (sub b) :M (sub s) , while not appreciably decreasing the number of screened earthquakes. This change also makes the variance of the earthquake and explosion populations more equal, which is of utility in statistical analysis. A slight trend in the explosion population and a case study of two large U.S. underground nuclear tests provide support for adopting a more conservative approach.