Acoustic microscopy of rocks

Abstract

SUMMARY Acoustic images of two common rocks, granodiorite and limestone, are studied to explore the kind of geological information that they can provide. The contrast is primarily due to Rayleigh waves; in rock specimens they are mainly affected in their propagation by crystal anisotropy and surface discontinuities. Therefore, acoustic microscopy makes possible detailed identification of intragranular structures in the rock‐forming minerals (very fine cracks, grain and subgrain boundaries, etc.); these features may appear more sharply than in transmitted polarized light microscopy or in scanning electron microscopy. In particular the acoustic images are effective in microfractographic studies, they can show not only the finest cracks, even those much less than a wavelength wide, but also their position in relation to the grain and subgrain structure.

Mechanical Compaction

“…introduced the procedure of ion-milling and attained a resolution of 0.02 µm of crack aperture. The acoustic microscope has also been used to delineate the cracks and mineralogical differences (Danburg and Yuhas, 1978;Briggs, 1992), and a resolution of about 1 µm can be obtained at a frequency of 1.6 GHz (Rodriguez-Rey et al, 1990).…”

Effects of pore and differential pressure on compressional wave velocity and quality factor in Berea and Michigan sandstones

“…Bulk and grain densities and porosity were determined by the Archimedes method. The microstructure of the samples was examined under optical microscope and scanning acoustic microscope (Briggs, 1985(Briggs, , 1992Rodriguez-Rey et al, 1990;Prasad et al, 1995).…”

Spherical inclusion characterization by the acoustical microscope: Axisymmetric case

“…Scanning acoustical microscopy or SAM has been used for imaging and characterizing many types of materialsceramics and composites, 1,2 rocks, 3 biological cells, 4 -6 semiconductors, and electronic materials, 7,8 to name a few. A good review of numerous applications of acoustical microscopy can be found in Ref.…”