Basic Research in Nuclear Test Monitoring: Seismic Wave Scattering from IrregularInterfaces

摘要

We report on two investigations of seismic wave scattering from irregularinterfaces. The first is a laboratory study of the scattering of ultrasonic waves incident on a glass surface etched to produce a highly irregular 3-D interface. We find that 2-D numerical simulations predict the 3-D experimental results well at small incident angles. Both numerical and experimental results strongly support the presence of enhanced backscattering. The second study is an analysis of regional P wave coda observed from events recorded at the Scandinavian NORESS, FINESA, and ARCESS arrays and the New England NYNEX array. The F-K spectra of the P coda are dominated by on-azimuth energy with apparent velocities between Pn (or faster) and Lg. Following this analysis, reflection coefficients calculated with a boundary integral scheme are used to study the role irregular interfaces play in the creation of regional P coda. We find that observed crustal scattering in these regions is strikingly consistent with P-P and P-SV scattering from the 2-D irregular Moho and even more consistent with scattering from a 2-D irregular near surface interface. (MM).