EFFECT OF A FLUID CORE ON PROPAGATION OF AN SH‐TORQUE PULSE FROM A POINT‐SOURCE IN A SPHERE

Abstract

An exact solution is obtained for the displacement of the surface of a sphere consisting of a fluid core and an elastic solid mantle, due to an impulsive SH‐torque source. Theoretical seismograms are computed for several distances from a surface source and from a deep source, and are compared with results for a homogeneous sphere. The seismograms show reflected pulses of H‐type and of Lg‐type, and pulses after diffraction at the core and at the surface. In agreement with observation and as expected by steepest‐descent analysis, it is found that the Lg‐type pulses start before the ray arrival time. Traveltime and amplitude curves for reflected and diffracted pulses are given.