Accession Number : ADA134501

Title :   Development of Ultrasonic Modeling Techniques for the Study of Crustal Inhomogeneities.

Descriptive Note : Final rept. 1 Jun 81-30 Sep 82,

Corporate Author : MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF EARTH AND PLANETARY SCIENCES

Personal Author(s) : Toksoz,M Nafi

PDF Url : ADA134501

Report Date : Aug 1983

Pagination or Media Count : 53

Abstract : The character of surface wave scattering at local distances depends strongly upon surface topography and local crustal structure. Ultrasonic methods were used to investigate the behavior of seismic waves propagating through scale models of topographic structures suspected of contributing to the scattering of seismic waves. Simple models, consisting of steps and rectangular-and triangular-shaped 'mountains' of varying dimension, were used in an empirical analysis of scattering of surface waves. Realistic seismograms were generated for a detailed scale model of the surface topography at Dry Valley Lake, Nevada. The addition of horizontal layers results in more complex seismograms, owing to dispersion and multiple reflections and conversions of the incident Rayleigh wave energy. Transmission of Rayleigh waves through the structure is improved with the addition of sedimentary layers. Finite difference methods were used to investigate the nature of the scattering produced by a scale rectangular 'mountain'. Upon encountering the 'mountain', the incident Rayleigh wave becomes severely distorted, and the 'mountain' re-radiates much of the incident energy in the form of body waves.

Descriptors :   *SEISMIC WAVES, SURFACE WAVES, RAYLEIGH WAVES, SCATTERING, EARTH CRUST, HOMOGENEITY, TOPOGRAPHY, TERRAIN MODELS, SCALE MODELS, ELECTROACOUSTIC TRANSDUCERS, ULTRASONIC RADIATION, LAYERS

Subject Categories : Seismology

Distribution Statement : APPROVED FOR PUBLIC RELEASE