Abstract

A method of constructing empirical travel-time curves from a sample of observed times has been programmed for computation on a high-speed data processing machine. The method reduces to a uniform procedure analysis hitherto successful in obtaining the standard travel-time tables, and its speed of operation promises to facilitate the construction of regional tables. The program processes up to 500 observations of the phase under revision, taken from any number of selected earthquakes. The hypocenter and time of origin of each shock are first adjusted by an automatic procedure previously described and the needed correction applied to the observed times. The corrected times are then weighted relative to a provisional travel-time table, and the weights used to fit polynomials up to a specified degree. Sample characteristics are also computed to facilitate statistical treatment. Preliminary results, obtained using the program to process PKIKP times from nine Aleutian shocks and a deep focus New Zealand shock, are presented. These results supply additional evidence that, relative to the standard P tables, J.-B. PKIKP times require the addition of about 1¼ sec.

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