Propagation of Elastic Waves in Ice. Part I

Abstract

Measurements of the velocity of sound vibrations in ice have been made in some detail both by direct and resonance methods. The velocity of longitudinal waves was measured directly on large bodies of ice. Blasting caps were used to create elastic disturbances and the time of travel was recorded by an electric seismograph placed at suitable distances. A plot of time against distance gives a remarkably straight line showing a velocity of 3410 m/sec. Laboratory measurements were made on long thin rods of ice which were excited by an oscillator and resonance frequencies measured both for longitudinal and torsional vibrations. The velocities for these vibrations are found to be 3163 m/sec. and 1913 m/sec., respectively. A formula is derived by which the velocity of longitudinal waves in a thin infinite plate can be found from these velocities. This formula gives a value of 3400 m/sec. which checks with that obtained directly by less than one percent. Various other elastic constants for ice are also deduced from these measurements. The values of Young's modulus and Poisson's ratio for ice are found to be 9.17×10¹⁰ dynes/cm² and 0.365, respectively, in the range −5°C to −15°C.