Statistical Characterization of Rugged Propagation Paths with Application to Rg Scattering Study
Abstract
Motivated by many observations of correlation between the free- surface topography and the coda generation at teleseismic and regional distances, seven simple statistics have been tested whether they can fully characterize the roughness of an arbitrary rugged free-surface topography. Based on 2-dimensional finite-difference simulations, the normalized arc length and Durbin-Watson number are identified as the best and the poorest, respectively, roughness measures, in terms of correlating with the propagation behavior of Rg. The numerical experiments show that rougher topography causes stronger attenuation (as expected), that reflection is an efficient process, and that the bulk of the energy which is not transmitted across the topography is either converted to body waves or reflected back. The scattered P and S waves are radiated as coda to teleseismic distances and some P-SV energy could be trapped in the crustal waveguide. The scattered body waves appear to radiate from the changes in slope and to first order can be visualized as from point diffractors along the rugged free-surface. Rg -to-S conversion is more efficient than that of Rg -to-P. The spatial Q values associated with rough topographic profiles range from 15 to 80, which are in excellent agreement with Q(Beta) Of the uppermost crust in many places of the world. The attenuation coefficient, gamma, and the scattering loss can be asymptotically represented as linear functions of the roughness parameters. This work offers a promising approach to quantify effects of scattering by topography and heterogeneity upon other regional phases.
Document Details
- Document Type
- Technical Report
- Publication Date
- Nov 05, 1993
- Accession Number
- ADA275237
Entities
People
- Rong-song Jih