Journal ArticleDOI
Elastic properties of marine sediments
TLDR
In this article, it was shown that for small stresses (such as from a sound wave), water-saturated sediments respond elastically, and that the elastic equations of the Hookean model can be used to compute unmeasured elastic constants.Abstract:
This report includes discussions of elastic and viscoelastic models for water-saturated porous media, and measurements and computations of elastic constants including compressibility, incompressibility (bulk modulus), rigidity (shear modulus), Lame's constant, Poisson's ratio, density, and compressional- and shear-wave velocity. The sediments involved are from three major physiographic provinces in the North Pacific and adjacent areas: continental terrace (shelf and slope), abyssal plain (turbidite), and abyssal hill (pelagic). It is concluded that for small stresses (such as from a sound wave), water-saturated sediments respond elastically, and that the elastic equations of the Hookean model can be used to compute unmeasured elastic constants. However, to account for wave attenuation, the favored model is ‘nearly elastic,’ or linear viscoelastic. In this model the rigidity modulus μ and Lame's constant λ in the equations of elasticity, are replaced by complex Lame constants (μ + iμ′) and (λ + iλ′), which are independent of frequency; μ and λ represent elastic response (as in the Hookean model), and iμ′ and iλ′ represent damping of wave energy. This model implies that wave velocities and the specific dissipation function 1/Q are independent of frequency, and attenuation in decibels per unit length varies linearly with frequency in the range from a few hertz to the megahertz range. The components of the water-mineral system bulk modulus are porosity, the bulk modulus of pore water, an aggregate bulk modulus of mineral grains, and a bulk modulus of the structure, or frame, formed by the mineral grains. Good values of these components are available in the literature, except for the frame bulk modulus. A relationship between porosity and dynamic frame bulk modulus was established that allowed computation of a system bulk modulus that was used with measured values of density and compressional-wave velocity to compute other elastic constants. Some average laboratory values for common sediment types are given. The underlying methods of computation should apply to any water-saturated sediment. If this is so, values given in this paper predict elastic constants for the major sediment types.read more
Citations
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Relationships between compressional‐wave and shear‐wave velocities in clastic silicate rocks
TL;DR: In this article, the authors analyzed new velocity data in addition to literature data derived from sonic log, seismic, and laboratory measurements for clastic silicate rocks and demonstrated simple systematic relationships between compressional and shear wave velocities.
Journal ArticleDOI
Controls on Sonic Velocity in Carbonates
TL;DR: In this article, compressive and shear-wave velocities of carbonate minicores from different areas and ages were measured under variable confining and porefluid pressures.
Journal ArticleDOI
Sediments with gas hydrates: Internal structure from seismic AVO
TL;DR: In this paper, the amplitude variation with offset (AVO) data from a bottom simulating reflector (BSR) offshore Florida was used to infer the internal structure of the hydrated sediment.
Journal ArticleDOI
Elasticity of marine sediments: Rock physics modeling
TL;DR: In this article, the elastic moduli of high-porosity ocean bottom sediments are calculated from those of the dry frame using Gassmann's equation, and the model assigns non-zero elastic constants to the dry-sediment frame and can predict the shear-wave velocity.
Journal ArticleDOI
Influence of gas hydrate morphology on the seismic velocities of sands
TL;DR: In this paper, the results of a series of resonant column tests on specimens where gas hydrate has been formed in sands using an "excess water" technique are reported.
References
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