Accession Number : ADA227337


Title :   Ocean Bottom Seismic Scattering


Descriptive Note : Doctoral thesis


Corporate Author : WOODS HOLE OCEANOGRAPHIC INSTITUTION MA


Personal Author(s) : Dougherty, Martin E


Full Text : https://apps.dtic.mil/dtic/tr/fulltext/u2/a227337.pdf


Report Date : Nov 1989


Pagination or Media Count : 310


Abstract : Seismic studies of the ocean crust, both experimental and theoretical, often assume a flat seafloor and laterally homogeneous crust. This is done regardless of the appearance in seismic data of obvious effects duet to scattering from lateral heterogeneities both on and in the seafloor. These heterogeneities have a significant effect on the propagation of seismo/acoustic energy through the crust, especially in the immediate vicinity of the seafloor. This thesis deals with the problem of scattering of seisom/acoustic energy from a number of forms of lateral heterogeneity in the upper in the upper oceanic crust. The finite difference formulation is used to study four distinct phenomena; scattering from discrete deterministic seafloor features; wave propagation through continuous randomly heterogeneous upper oceanic crust; scattering from more complicated topographic profiles and the limitations of the method for the rough seafloor problem; and the problem of plane acoustic wave scattering from an infinite elastic cylinder. The principal finding of this work is that lateral heterogeneities in the upper oceanic crust can have a dramatic affect on seismo/acoustic wave propagation. Scattering from rough seafloors and/ or volume heterogeneities is often quite similar and causes the occurrence of signal generated 'noise' (coda), decorrelation of primary arrivals, and anomalies in arrival time and amplitude. Topographic and volume scatters acting as secondary sources of seismic energy can cause a resonant coupling of body wave energy into interface (Stoneley) waves at the seafloor. Theses.


Descriptors :   *PROFILES , *OCEANIC CRUST , *SEISMIC DATA , *SEISMOLOGY , *OCEAN BOTTOM TOPOGRAPHY , ACOUSTIC WAVES , ENERGY , ELASTIC PROPERTIES , THESES , TOPOGRAPHY , TIME , FINITE DIFFERENCE THEORY , WAVE PROPAGATION , CYLINDRICAL BODIES , SIGNALS , RESONANCE , SEISMIC WAVES , HETEROGENEITY , NOISE , ARRIVAL , ROUGHNESS , PLANE WAVES , DETERMINANTS(MATHEMATICS) , WAVES , FORMULAS(MATHEMATICS) , SECONDARY , SCATTERING , VOLUME , HOMOGENEITY , COUPLING(INTERACTION) , SOURCES


Subject Categories : Seismology


Distribution Statement : APPROVED FOR PUBLIC RELEASE