Accession Number:

ADA327296

Title:

Ocean Bottom/Subbottom Seismic-Acoustic Scattering with Realistic Sediment Properties,

Descriptive Note:

Corporate Author:

STANFORD UNIV CA DEPT OF GEOPHYSICS

Personal Author(s):

Report Date:

1995-06-01

Pagination or Media Count:

40.0

Abstract:

This proposal addresses two related aspects of the acoustic reverberation problem, namely 1 seismic-acoustic properties of ocean bottomsubbottom sediments, and 2 the short range scattering of acousticelastic waves at the rough and heterogeneous bottomsubbottom interface zone. The primary objective of the proposed research is to quantify the importance of bottomsubbottom scattering of compressional and converted shear waves. The approach is to numerically simulate short range scattering using realistic models for the geometry, scales, and vertical and lateral variations in material properties of the ocean bottom and especially subbottom. To treat this problem realistically, a numerical model for constrained sedimentological deposition of sands and clays over basement rock is used to describe the three dimensional geometry of sediment beds and laminae over basement rock. Models for rock properties are then used to determine the seismic velocity, attenuation, density, porosity, and permeability for the suspended and loosely consolidated granular sediment materials and basement rocks. This geological model is then used in three dimensional seismic-acoustic simulators to predict the acoustic fields scattered by the rocks at and below the interface. Two preliminary finding of results by us to date are noteworthy First, acoustic scattering is completely inadequate for describing the interaction, particularly near grazing angles where the elastic boundary conditions play a critical role in establishing the energy balance.

Subject Categories:

  • Physical and Dynamic Oceanography
  • Geology, Geochemistry and Mineralogy
  • Seismology

Distribution Statement:

APPROVED FOR PUBLIC RELEASE