Seismic reflection and refraction methods measure which properties of geological materials?

Seismic reflection and refraction methods measure which properties of geological materials?

• A. Elastic moduli and density
• B. Porosity and permeability
• C. Thermal conductivity and grain size
• D. Magnetic susceptibility and density

Answer: (A)

Seismic reflection and refraction experiments reveal how rocks respond to elastic waves. The speeds of compressional (P) and shear (S) waves depend on the rock’s stiffness (its elastic moduli) and its density. In isotropic rock, Vp and Vs are related to the bulk and shear moduli and to density, so from measured velocities (and any available density data) you can derive elastic moduli such as the bulk modulus, shear modulus, Young’s modulus, and Poisson’s ratio. Reflections arise from impedance contrasts, where impedance is density times velocity; this is why seismic data map layering in terms of how stiff and dense the rocks are. So the properties you’re inferring are elastic moduli and density, not porosity/permeability, thermal conductivity, grain size, or magnetic susceptibility, which seismic data do not measure directly.

Seismic reflection and refraction experiments reveal how rocks respond to elastic waves. The speeds of compressional (P) and shear (S) waves depend on the rock’s stiffness (its elastic moduli) and its density. In isotropic rock, Vp and Vs are related to the bulk and shear moduli and to density, so from measured velocities (and any available density data) you can derive elastic moduli such as the bulk modulus, shear modulus, Young’s modulus, and Poisson’s ratio. Reflections arise from impedance contrasts, where impedance is density times velocity; this is why seismic data map layering in terms of how stiff and dense the rocks are. So the properties you’re inferring are elastic moduli and density, not porosity/permeability, thermal conductivity, grain size, or magnetic susceptibility, which seismic data do not measure directly.