Abstract

Influence of Elastic Nonlinearity of the Earth.S Crust on Regional and Teleseismic Waves Generated by Underground Nuclear Explosions

A.M.Ionov (Department "Modeling of Physical Processes in the Environment" (No.39), Moscow Engineering Physics Institute (State University), Moscow, Russia)

e-mail: aionov@hotmail.com

The effect of elastic nonlinearity of the Earth.s crust on regional and teleseismic body phases induced by underground nuclear explosions is investigated in this paper. A considerable contribution to the results predicted by the linear theory should be expected, because the upper crust is characterized by anomalously high magnitudes of the nonlinear parameter. The analysis is based on the evolution equation derived earlier [Ionov A.M., Sirotkin V.K. About asymptotic behaviour of acoustic signal radiated by a spherical source in a nonlinear absorbing medium. Acoust. Phys., 1989, V.25, No. 5], which takes into account nonlinear, absorbing and inhomogeneous properties of the Earth.s interior. An expression for the efficient reduced velocity potential, including the integrated nonlinear properties of the Earth.s crust near the source, is obtained. It is shown that the overall influence of the crustal elastic nonlinearity near the source can increase the P-wave amplitude at the most twice. A local peak is generated in the high-frequency range of the radiated signal due to the integrated nonlinear effects along a path. Separation of the effects contributed by the crustal nonlinearity in the high-frequency range of the signal could be used as an additional criterion for yield estimation.

Section : 6