Use of long-period surface waves for determination of elastic and petrological properties of ice masses

Abstract

Elastic wave propagation has proved to be a powerful tool in the study of the mechanical properties and thicknesses of ice masses. The anisotropy, heterogeneity, and departure from perfect elasticity that plague conventional static tests can all be studied in detail by seismic techniques that have been developed for use both in the field and in the laboratory. Two types of elastic waves can be transmitted by an unbounded, isotropic, elastic media: the dilational and distortional. The velocities of these two waves, along with the density, completely describe the elastic behavior of an extended elastic body. In an inhomogeneous, anisotropic, and imperfectly elastic solid body, these basic wave types are modified. Bounded media will transmit, in addition, guided waves that can be used to give further information on elastic properties. The combined use of body wave and guided wave data permit a detailed description to be made of the mechanical properties of a bounded body, such as a sea ice sheet or a glacier. The same battery of elastic waves can be applied in the laboratory, where the seismic, or ultrasonic, method becomes a sensitive analytical tool for the determination of composition and structure.