m_b: M_s Screening Revisited for Large Events

摘要

Event screening of large-magnitude events (M_w ?5) based on m_b: M_s is revisited to account for the effect of the source corner frequency relative to the fixed frequencies of the long-period M_s and short-period m_b. For large events this source effect increases the slope of m_b: M_s relative to the 1:1 value expected for small events. The effect is demonstrated in the large earthquake m_b: M_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_b: M_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.