Discrimination of Problem Seismic Events by Modeling the Combined Effects of Deterministic and Statistical Structure on Regional Seismograms

Monitoring the Comprehensive Nuclear Test Ban Treaty requires analysts to discriminate seismic signals generated by earthquakes vs nuclear explosions. Seismologists are generally able to discriminate large energy events (> 5 mb) at teleseismic distances (greater than about 1,000 km). However, lower energy events need to be analyzed at regional distances because the energy attenuates with distance. At regional distances (< 1,000 km), the seismic energy travels primarily through the Earth’s crust and can be affected by large- and small-scale crustal structures. This can have the effect of making earthquakes look more like explosions and vice versa and is very dependent on the region through which the energy travels. Therefore new methods are needed to assist in the discrimination of events recorded at regional distances. The work discussed here uses a new computer code to model the combined effects of known 3-D relatively large (deterministic) Earth structures and relatively small (statistical) structures to generate improved structural models and evaluate the performance of yield estimators and discriminants at selected seismic stations in Eurasia. This is accomplished by synthesizing seismograms using a radiative transpor