Low-yield seismic source analysis and discrimination using local to regional seismic observations

Low-yield seismic source analysis and discrimination using local to regional seismic observations Low-yield explosion monitoring introduces new challenges to current monitoring capabilities. Small-source monitoring requires near source and short-period observations, which often means the number of stations that provide useful signals is limited. Additionally, for some analyses, reliance on short-period observations increases the sensitivity of the inferences drawn from the data to geologic heterogeneity. Successful low-yield source monitoring requires (1) exploiting the dominant and stable features in local- to nearregional seismic observations and (2) understanding the physical basis of explosion discriminants so they can be effectively applied at both local and regional distances and appraised in all cases. Our study of low-yield seismic events will focus on three of the fundamental tools used in nuclear monitoring: estimation of event location and yield, and source-type discrimination. We will investigate the potential to provide increased-precision relative event locations using fundamental-mode Rayleigh waves (Rg) jointly with all other coherent phases. We will test the transportability of MRg, a magnitude based on Rg, which has shown promising results for use constructing magnitude-yield relationships, by exploring its sensitivity to topography, near-surface geology, source depth, as well as azimuthal amplitude variability. Finally, empirically-based P/S ratios are a critical earthquake-explosion discriminate. By analyzing multiple source types and emplacement conditions, we will investigate the sensitivities of short-period P/S ratio discriminants at local to near-regional distances and with a goal to develop a physical understanding of the sensitivities of the discriminants. To accomplish these goals, we will exploit three unique, high-quality local- to regional-distance seismic datasets that provide a diversity and abundance of seismic sources located at shallow source depths (0- 4 km). Results from this study will not only advance our capabilities to locate and to identify lowyield seismic events but will help quantify the sensitivities and map the limitations of current explosion monitoring tools