THE SEISMOLOGICAL IMPLICATIONS OF AEOLOTROPY IN CONTINENTAL STRUCTURE

Abstract

The seismological consequences of a departure from isotropy in the surface layers of the Earth are discussed. It is noted that erroneous values of the focal depth and the thickness of the layers might be found in near earthquakes. For a transversely isotropic continent it is shown that SH waves would travel with a different velocity from that of SV, and that the law of variation of velocity with direction is different. With body waves the sharp distinction into compressional and distortional waves does not hold, and an explosion would generate an S wave as well as a P wave; an apparent difference in the instant of generation of P and S might arise. It is proved that waves of the Rayleigh type can be propagated over the surface of a transversely isotropic body in which the axis of circular symmetry is normal to the free surface, supposed plane; in such waves the diminution of amplitude with depth is different from that in an isotropic body, so that the amplitudes of the surface waves generated by a source at a given depth will be different from what they would be in an isotropic medium. Love waves can be propagated as in isotropic media. Copyright © 1949, Wiley Blackwell. All rights reserved