Earth surface displacement generated by propagation of acoustic plane waves within a gas-filled buried pipe (theoretical)

Abstract

The theory of surface displacements caused by acoustic plane progressive wave propagating at frequencies of 200–2000 Hz in the gas within a pipe buried in the earth is presented. It is shown that in order to satisfy the boundary conditions at the pipe—earth interface both shear and compressional waves must be excited and that these waves interfere with each other at the surface of the earth, giving a series of maxima and minima separated by about 275 Hz. This interference is a consequence of the large difference between velocities of propagation of compressional and shear waves in the earth medium. Dependence of the magnitude and character of radiation from the pipe walls into the earth medium on these velocities will be discussed. [Work supported by the American Gas Association.]