Surface Wave Attenuation
Abstract
Amplitude spectra for the fundamental Rayleigh mode and for the combined higher Rayleigh modes are used to infer crustal models of shear wave internal friction for a region of the Middle East between southern Iran and western Turkey. This recently developed method requires only a single source and single receiver; thus, it is useful for obtaining shear wave internal friction models for relatively small regions. The model which provides the best fit to the amplitude spectra throughout most of the Iranian Plateau and Turkey consists of a 20 km thick upper crust with an attenuation value of 85 overlying a lower crust with a value of about 300 for shear waves. Data for the region around Meshed, Iran, are, however, better explained by a model in which the upper crust is 33 km thick and is comprised of rock having an average shear attenuation value of about 75. To aid in the problems of detecting and identifying underground nuclear explosions in the U.S.S.R. using regional seismic data, a study of Lg waves generated by explosions and earthquakes within the U.S.S.R. was begun. Attenuation of 1-Hz waves was determined using the coda method recently described by Herrmann. Preliminary results indicate that attenuation for 1-Hz Lg waves is approximately 900 for the interior of the U.S.S.R., similar to that in the eastern United States. High mountains and deep seas reduce this value.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 30, 1980
- Accession Number
- ADA096959
Entities
People
- Brian J. Mitchell
- Otto W. Nuttli
Organizations
- Saint Louis University