ASA 129th Meeting - Washington, DC - 1995 May 30 .. Jun 06

5aPA10. Observation of seismic wave propagation in particulate composite material with various inclusion sizes and concentrations.

Seiji Nakagawa

Neville G. W. Cook

Dept. of Mater. Sci. & Mineral Eng., Univ. of California, Berkeley, CA 94720

K. T. Nihei

L. R. Myer

Lawrence Berkeley Laboratory, Berkeley, CA 94720

Two-phase particulate composite samples with inclusions of varying size and concentration were made with cement and sand or pebbles. The velocities of P-wave (60-kHz) and S-wave (150-kHz) pulses and the attenuation of S-wave pulses were examined. The results of the tests suggested that the velocities were consistent with the results of effective media models which were inclusion size independent. However, the frequency-dependent attenuation of the S wave was strongly affected by the size of the inclusions. For inclusions sized on the order of 1/10 of the wavelength, the waves showed decreasing attenuation with increasing concentration, while for the sizes of about 1/4 and 1/1 of the wavelength, the waves showed maximum attenuation at volumetric concentrations of about 30% and 70%, respectively. Many aspects of the observed wave behavior for moderate concentrations were similar to numerical simulations of 1-D wave propagation in a layered media, where the matrix and inclusions were represented by alternating layers with different seismic properties and stochastically varied thicknesses. [Work supported by NSF.]