Earlier studies of the velocity distribution in the outer core have been based on the travel times of SKS.SKS arrivals can only be observed satisfactorily for arc distances at the surface greater than 85°. This lower limit of observation of SKS corresponds to an arc distance of 40.2° within the core. Thus the velocities in the outermost 250 km of the core are based upon an extrapolation. We have used observations of the difference in time of arrival of SKKS and SKS to obtain core travel times extending the range of observation down to a Δ within the core of about 14°. The velocity distribution thus found is significantly lower than those of Jeffreys (Bullen, 1963) and Randall (in press) near the core mantle boundary.

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