Seismic surveillance - nuclear test ban verification. Final report, 1 Jan 89-31 Dec 91

The project is aimed at seismic surveillance as part of on-going efforts for improving nuclear test ban verification capabilities. The problem is complex in the sense that underground explosions are most efficiently monitored by seismic means, but that the distinction between signals emitted by natural earthquakes and explosions remains unclear, at least at local and regional distances. In other words, seismic wave propagation in a heterogeneous Earth may easily mask specific source signatures. Section 2 reports on major results from a marine seismic reflection survey in the Skagerrak Sea and the outer Oslo Fjord. In section 3 an experiment is described by which the detector described in Ruud and Husebye (1992) is used for automatically picking P- and S- arrivals in local event records stemming from the Norwegian Seismic Network. In Section 4 two works are presented addressing the problem of seismic wave propagation in inhomogeneous media. Details are given on the methodology used for computing synthetic seismograms from 2D finite difference (FD) solutions of the elastic wave equation. The first attempt on seismic discrimination between earthquakes and underground nuclear explosions is documented in Section 5. This problem is formulated as an exercise in pattern recognition approach analysis. The principalmore » aim of this study was to explore the range of crust/lithosphere structural models which were capable of producing strong and persistent coda waves commonly observed at local and regional distances.« less