Development of Ultrasonic Modeling Techniques for the Study of Crustal Inhomogeneities,
Abstract
The effects of topographic features on Rayleigh wave propagation and scattering are investigated in the laboratory using three-dimensional ultrasonic models. The effects of different topographic features on Rayleigh wave transmission and scattering are examined as a function of wavelength and of angle of incidence. In general, backscattered or reflected Rayleigh waves are small compared to transmitted waves. A significant fraction of the Rayleigh wave energy is scattered into body waves. Transmission and reflection coefficients (transmitted or reflected energy scattered into body wave ranges from more than 90% at normal incidence to about zero at near-grazing incidence. At each angle, transmission coefficients vary strongly with frequency. Because of frequency-dependent phase shifts, the transmitted and reflected waves are distorted. The effect of the steps on wave propagation is demonstrated by convolving synthetic dispersed wave trains with the impulse response of the scale models. The ocean-continent margin of the western United States is modelled as a 60 deg ramp scaled to 60 km height. The Tibetan Plateau is modeled as a broad mesa scaled up to 40 km height. In both models the azimuthal dependence of transmitted Rayleigh waves is similar to that observed at WWSSN stations for Rayleigh waves crossing the modeled terrestrial structures.
Document Details
- Document Type
- Technical Report
- Publication Date
- Aug 01, 1984
- Accession Number
- ADA155206
Entities
People
- J. T. Bullitt
- M. Nafi Toksöz
Organizations
- Massachusetts Institute of Technology