Development of Surface Wave Dispersion and Attenuation Maps and Improved Methods for Measuring Surface Waves
Abstract
The objective of this project is to optimize measurement of surface waves, particularly at regional and local distances and at periods of 8-15 s. An important part of the project is the development of global regionalized dispersion and attenuation maps, with a particular focus on determining attenuation maps for Eurasia in the 8-15 s period band. Both the dispersion and attenuation maps are corrected for scattering and diffraction from heterogeneous earth structure, and amplitude correction "maps" are also being developed. Surface wave propagation in the frequency band of interest is strongly affected by heterogeneous earth structure as well as attenuation, particularly along paths crossing deep sedimentary basins. Two such basins of interest in Eurasia are the Tarim Basin in Western China, and the West Siberian Basin. Explosions within these basins generate unusually high amplitude and persistent high frequency fundamental mode surface waves. The Quartz3 and Kimberlite peaceful nuclear explosions (PNEs) were conducted in the West Siberian Basin, and their data give a particularly good sampling of the surface wave propagation access the basin, so we are analyzing these events in detail. We implemented the algorithm of Zhou et al. (2004) for calculating finite frequency sensitivity kernels for dispersion and amplitude variations, and have been testing the algorithms using the one-degree dispersion maps of Stevens et al. (2005). We performed a large test inversion similar to our earlier great circle path inversions, but using the finite frequency sensitivity kernels. While the inversion looks reasonable, it is not yet clear whether the results fit the data significantly better than the simpler great-circle representation. Amplitude corrections predicted by the Born approximation for the one degree model seem unreasonably large on long paths. This likely reflects the limit of the approximation when large velocity contrasts are encountered.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 01, 2006
- Accession Number
- ADA462265
Entities
People
- G. E. Baker
- Heming Xu
- Jeffrey W. Given
- Jeffry L. Stevens
Organizations
- Leidos